Forensic Chemistry and Toxicology Syllabi/Table of Specification

The registered criminologist can perform the competencies under the following sub-topics:

  1. Explain the principles of forensic chemistry and toxicology with crime detection and investigation
  2. Demonstrate accepted protocols for handling chemical and biological evidence (blood, semen, fiber, explosives, drugs, etc.) from the crime scene to the courtroom
  3. Recognize standardized tests and appropriate laboratory equipment in processing biological evidence and physical evidence
  4. Apply scientific procedures in the recognition, collection, and preservation of drugs, poisons, and other toxicological concerns
  5. Generate case reports and present factual reports in support of a court trial

Forensic Chemistry is defined as that branch of Chemistry that deals with the application of chemical principles in the solution of crimes. Like the other forensic sciences, Forensic Chemistry plays a very important part in the speedy investigation and in the administration of justice.


- Identification of evidence, and its physical and chemical properties. 

- Collection, preservation, examination, and study of blood, semen, and other body fluids; 

- examination of dangerous drugs; 

- examination of body fluid to determine the presence of dangerous drugs;

- Alcohol (liquor) test; examination of fake products for unfair trade competition; 

- arson investigation; 

- macro etching examination;

- bullet trajectory; 

- ultraviolet examination

- tools and other marks;

- gunshot residues (gunpowder nitrates, paraffin test; distance determination; and firearms examination);

- principles and examination of explosives, hair, and textile fibers

- chemical aspects of document and examination;

- problems with glass fragments and glass fractures, 

- moulage, metallurgy, and petrography as applied to crime investigation. 

- Forensic Chemistry also includes the study and examination of Deoxyribonucleic acid or DNA for brevity. (Case of Webb)

Forensic Toxicology deals with the examination of human internal organs, food samples, and water and gastric contents to detect the presence of poisonous substances, their dosage, effects, and treatment. 

The work of a Forensic Chemist is divided into four stages, namely:

1. Collection or reception of the specimen

2. The actual examination

3. The communication of the results of the examination

4. Court appearance.

Equipment Used in the Forensic Examination

The following are some of the most common laboratory equipment used in forensic examination:

1. HPLC (High Powered Liquid Chromatography) 

This scientific equipment is used for the qualitative and quantitative determination of a volatile or non-volatile compound based on the chromatographic separation of its components.

2. Ultra-violet spectrophotometer

It is used for the qualitative and quantitative analysis of organic compounds.

3. EMIT (Enzyme Multiple Immuno Assay Technique)

It is used for screening of abused urine samples.

4. SEM (Scanning Electron Microscope)

This scientific equipment is used for the physical identification of various questioned specimens. It is a software-controlled digital scanning electron microscope used to produce sticking images over a wide range of magnification (3x3,000,000x) on rough or covered surfaces of minute specimens such as hair, fibers, paint particles, drugs, metal, etc.

5. FTIR (Fourier Transform Infrared Spectroscopy)

Used for the identification of pure organic substances. It identifies organic substances particularly abused drugs and explosive ingredients based on their characteristic functional groups. In layman’s terms, the resulting spectrum could be referred to as the fingerprints of the substance.

Scientific Evidence

Evidence is a proof of allegation, it is a means sanctioned by law of ascertaining in a judicial proceeding the truth respecting a matter of fact (Sec Rule 128,   Revised Rules on Evidence). 

Such scientific evidence must have such a relation to the fact in issue as to induce belief in its existence or non-existence.

Evidence may be  

(a) direct;   

(b) indirect, which includes circumstantial evidence; and 

(c) hearsay.

Forms of Scientific Evidence

(a) Real or Autoptic evidence –  is that evidence which is addressed to the senses of the court. It is not limited to that which can be known by the sense of vision but extends to those which are perceived by the senses of hearing, taste, smell, or touch.

(b) Testimonial Evidence – An expert may be called on the witness stand to answer all questions propounded by both parties in the case. (Oral testimony)

(c) Documentary evidence – Any written evidence presented by an expert in court that is relevant to the subject matter in dispute and not excluded by the Rules of   Court. Formal written reports, expert opinions, certificates, and dispositions are included in this group.


Witness defined.

A witness in court may be an ordinary or expert witness.

This kind of evidence is called the testimony of an expert witness.

Distinctions between an ordinary witness and an expert witness

Ordinary witness

1. Can only state what his senses have perceived.

2. May not be skilled on the line he is testifying.

3. Cannot testify on things or facts he has not perceived except those provided for by law.

Expert witness

1. State what he has perceived and also give his opinion, deductions, or conclusions to his perception.

2. Must be skilled in the art, science, or trade he is testifying.

3. Testify on things that he has not seen by giving his opinions, deductions, or conclusions on the statements of facts.


Drug defined.

A drug is a chemical substance that brings about physical, physiological, behavioral, and/or psychological changes in a person taking it.

All medicines are drugs, but not all drugs are medicine drugs.

Medicinal Drugs

A substance which when taken into the human body cures illness and/or relieves signs/symptoms of disease.

Dangerous Drugs

A substance affecting the central nervous system which when taken into the human body brings about physical, emotional, or behavioral changes in a person taking it.

Drug Abuse

Any non-medical use of drugs that causes physical, psychological, legal, economic, or social damage to the user or to people affected by the user’s behavior.

Abuse usually refers to illegal drugs but may also apply to drugs that are available legally, such as prescribed medications and certain over-the-counter medications.


According to origin:

a.  Natural Drugs  - are active ingredients, secondary metabolic products of plants, and other living systems that may be isolated by extraction.


Raw opium


Coca bush

b. Synthetic Drugs  –   are artificially produced substances, synthesized in the laboratory for the illicit market, which are almost wholly manufactured from chemical compounds in illicit laboratories.




According to Legal classification: 

a. RA   9165   (Comprehensive Dangerous Drug Act of 2002)

b. PD 1619 (Volatile Substances)

c. RA 6425 (Classified as Regulated and Prohibited)

Under RA 9165, otherwise known as the Comprehensive Dangerous Drugs Act of 2002, the term prohibited and regulated was changed into  dangerous drug with the following classification:

1.  Immediate precursors  –   a chemical substance used in the clandestine manufacturing process becomes incorporated in full or in part into the final molecules of a substance under international control.

2. Essential chemicals – chemical substances used as reagents or solvents in the illegal manufacture of controlled substances.

3. Narcotic, psychotropic, and designer

According to International Classification:

a. Narcotics substance

b. Psychotropic substances

c. Designer drugs

According to Pharmacological Classification (Effects):

a. Stimulants

b. Hallucinogens

c. Depressants

d. Inhalants

STIMULANTS  – are drugs that increase the alertness of physical disposition

Example: Amphetamine

Street Name: Eye   opener,   lid   poppers,   pep   pills,  uppers, hearts

What it is: Reduces appetite Relieves mental depression Comfort fatigue and sleepiness

Example: Shabu   (Methamphetamine Hydrochloride)

Street Name: Poor Man’s Cocaine, S, shabs, ubas, siopao, sha,

HALLUCINOGENS - are drugs that affect sensation, thinking, self-awareness, and emotion.

Example: Ecstacy

Street Name:  XTC, Adam, essence, E, herbals           

LSD (Lysergic Acid Diethylamide) 


Street Name: Mary Jane, Flower, pampapogi, brownies, Damo, pot, tea, joint, Dope Comes from Cannabis Sativa L.(Indian hemp);  looks like fine, green tobacco

DEPRESSANTS – are drugs which depress or lower the functions of the Central Nervous System

Types of Depressants:

Narcotics –  a drug that induces sleep  (Hypnotics)or stupor and relieves pain (Analgesics)

Tranquilizers  –  a substance that reduces anxiety, eases tension and relaxes muscles.

Sedatives and Hypnotics – calm the nerves, reduce tension, and induce sleep. Example: Barbiturates, alcohol

INHALANTS – these are any liquid, solid, or mixed substance that has the property of releasing toxic(psychoactive) vapors or fumes.

Examples: solvent, glue, gasoline, kerosene, paint, thinner, naphthalene.

What are considered Dangerous Drugs?

A Dangerous Drug is a substance affecting the central nervous system which when taken into the human body brings about physical, emotional, or behavioral changes in a person taking it.

It is a substance that when taken into the human body alters mood, perception, feelings, and behavior.

Under Republic Act 6425, otherwise known as the Dangerous Drugs Act of 1972, dangerous drugs are classified into three (3) main categories, namely:

A. Prohibited Drugs

B. Regulated Drugs

C. Volatile Substances

Republic Act 9165, otherwise known as the Dangerous Drugs Act of 2002, gives a single definition for prohibited and regulated drugs. The old law defines the term “dangerous drugs” as either a “prohibited drug” or a “regulated drug”.“

Drug Dependence” – means a state of psychological or physical dependence, or both, on a dangerous drug, arising in a person following administration or use of that drug on a periodic or continuous basis.


Drug Identification – is a branch of Forensic Chemistry that deals with the scientific examination of drugs and volatile substances.

Forms of Dangerous Drugs

Drugs are in various forms. This includes tablets, capsules, liquid, powder, brick or decks of marijuana, crushed leaves, and uprooted plants.

A. Examination of the sample taken from the alleged confiscated Dangerous Drugs

Methods of Examination

1. Qualitative examination

2. Quantitative examination

Two phases in the examination of the alleged confiscated Dangerous Drugs

1. Screening test/Preliminary test (also known as the color test)

This test is nonspecific and preliminary in nature. It is employed to reduce the family or group of drugs to a small and manageable number.

Screening test includes a series of color tests producing characteristic colors for each family or group of drugs. This is done by adding a specific reagent to an unknown sample in a spot plate.

Color Reactions:

Upon addition of specific reagents to a sample of dangerous drugs, a specific color reaction is produced such as:


Duquenois-Levin = violet

Fast Blue B salt = purple-red


Cobalt Thiocyanate test or CT test = blue

Scott test or Modified CT test:                           

Reagent 1 = blue            

Reagent 2 = pink

Reagent 3 = blue

Wagner test = brown (specific test for cocaine)

Diazepam: Zimmerman   test   =   reddish  purple  or  pink(some benzodiazepine derivatives do not give color with this test)

Hydrochloric acid = yellow

Vitali-Morin test = yellow orange

Opium: Marquis = violet

Ferric Sulfate = Brownish purple

Mecke = Blue to green

Nitric acid = Orange to red to yellow


Marquis = Violet to reddish-purple


Mecke = Blue to green 

Nitric acid = Orange to yellow


Mecke = Blue to green

Nitric acid = Yellow to green

Dille-Koppanyi test = reddish purple (for barbiturates)

Methamphetamine Hydrochloride: 

Simon test = Blue

Marquis test = Orange to brown


Simon test = Blue

Methaqualone and Phencyclidine: 

CT test =blue

Lysergide or LSD: 

Ehrlich = violet


Marquis test = Orange

Liebermann = black


It must be noted that the Positive results of these tests are not conclusive, as there are substances that may give the same positive color reaction/s upon the addition of the specific reagents. Hence, confirmatory tests must be performed by the Forensic Chemist/Chemical officer on the case to establish the presence and identification of dangerous drugs. It must also be noted that only those specimens that yielded presumptive positive results are subject to confirmatory tests to confirm if the positive result of the screening test is really positive.

2. Confirmatory Test

A confirmatory test is the method employed to confirm the results of the screening/preliminary test. This test involves the application of an analytical procedure to identify the presence of a specific drug or metabolite. This is independent of the screening test and which uses techniques and chemical principles different from that of the initial test to ensure reliability and accuracy. 

There are several methods used in the confirmatory test. Some of these methods are:

Chromatography  – is the process of separating the mixture and comparing the migration of each component with the standard. Some chromatographic techniques include:

Gas chromatography

Thin Layer chromatography

High-Pressure Liquid chromatography

What is a GAS Chromatography?

- It is a separate technique

- The mobile phase is a gas

- Separation is based on the difference in migration rates among sample components.

Spectroscopy – a confirmatory method whereby light is used to identify the sample specimen.

Fourier   –  Transform   Infrared  Spectroscopy(FTIR) - Used for the identification of pure organic substances. Identifies organic substances particularly dangerous drugs and explosive ingredients based on their characteristic functional groups. Inlayman’s term, the resulting spectrum could be referred to as the fingerprints of the substance.

Ultraviolet-visible spectroscopy – Used for screening of dangerous drugs in urine specimens.


Basically, gunshot residue comes from the powder component of the bullet and elements from cartridge cases and gun barrels where the bullet passes. When these components are burned, certain products of combustion are formed which include partially burned and unburned particles. These particles are deposited on the target as a definite pattern depending upon the distance between the muzzle of the gun and the target at the time of discharge.

Upon discharge of the firearm, gunpowder residues(nitrates) may be deposited on a person at close proximity, so the interpretations as to who discharged the firearm should be made with caution. (Thorton, 1986) A hand or body part close to the fired weapon may have gunpowder residues consistent with having discharged the weapon. However, the absence of gunpowder residues on the person’s hands or body parts does not mean that he/she did not discharge a firearm.

Gunpowder residue may be found on the skin or clothing of the person who discharged the gun, on the entrance bullet hole of the garment or wound of the victim, or on other target materials at the scene.

Components of gunshot residue

1. Primer or lead residue

2. Gunpowder residue

3. Elemental components from cartridge case residues

Composition of Primer

Primer elements may be easier to detect in residues because they do not get as hot as that powder. 

Types of gunpowder

1. Single-based - when the basic ingredient is nitrocellulose

2. Double based   - nitrocellulose + 1 to 40% nitroglycerine

3. Triple based   - nitrocellulose + nitroglycerine + nitroguanidine.

These can be differentiated using a mass spectrophotometer.

Composition of cartridge case, bullet coating, and metal jacket

1. Cartridge and primer cases; BRASS (7:3  COPPER-ZINC)

2. Bullet cores: lead, lead, antimony, and a few iron alloy

3. Bullet jackets: brass (9:1   copper-zinc), some are iron or aluminum alloy. Some contain nickel.



Gunshot residue examinations are performed to help the investigators in determining whether a person has discharged/fired a firearm/gun or not; whether a firearm was discharged or not; and the possible gunshot range or the distance of the shooter to the victim. Both hands of the suspect, as well as those of the victim, the firearms, and clothing of the victim, must be examined to determine the presence of gunpowder nitrates.

Types of Powder used in the ammunition of small firearms

There are two types of powder used in the ammunition of small firearms. These are:

1. Black Powder - this consists of a mixture of carbon(Charcoal), sulfur, and potassium nitrate. This mixture is used as an igniter in smokeless gun propellant. It consists of a mixture of 15% Charcoal, 10% Sulfur and 75% Potassium nitrates.   Aluminum is added to enhance the burning property. When this powder is burned, a combustion reaction takes place:

2KNO3 + 2o2 + S + C  CO2 + SO2 + k2O2 + 2NO2

2. Smokeless Powder - This mixture consists of Cellulose or glycerol nitrate combined with some stabilizers (nitrobenzene or graphite nitrates, dichromate, and oxalates). When this powder explodes, the chemical reaction takes placeCellulose nitrate: C12H14O4(NO3)6 + 6H2O+3N2+4CO2+8CO+H2

Glycerol nitrate : C3H5(NO3)3 + CO2 + H2O + N2 + O2


To explode a low explosive, flame is required. In guns, the flame is applied by means of a primer. Primer produces flame on percussion. A typical primer consists of a case containing an initiating explosive such as mercury culminate, an oxidizing agent such as potassium chlorate or barium nitrate, and a fuel such as antimony sulfide. This component is the basis for the examination of gunshot residue particularly primer residues for distance determination.


The following are common methods used by most crime laboratories to detect gunshot residue:

1. Paraffin test (most common in the practice)

2. Lead residue (detection limit: up to 30 feet and always present on the opposite sides of the penetrated target). Reported from intermediate glass target present.

3. Gunpowder residue examination (detection limit: highly variable up to 20 cm, and up to 21 inches is common)

4. Other examinations

The last two methods are classical. Color development or modern methods such as Neutron Activation  Analysis(NAA), atomic absorption spectrophotometry (AAS), Scanning Electron microscopy with energy dispersive analysis (SEM-EDA), and inductively coupled plasma with mass spectrophotometry (ICP-MS) are used. History of Paraffin test/dermal nitrate or Diphenylaminetest.

The Paraffin test originated in Cuba when  Dr.Gonzalo Iturrios first used paraffin for collecting gunpowder residues from a discharged firearm. In 1933, Teodoro Gonzales of Criminal Identification Laboratory, Mexico City introduced the test in the United States. In this test, the hands were coated with a layer of melted paraffin. After cooling, the casts were removed and treated with Diphenylamine (5% DPA in 60% sulfuric).

Methods of Examination

Paraffin Test

To determine whether a person has discharged a firearm, the Paraffin–Diphenylamine test is used. The basis of this test is the presence of nitrates in the gunpowder residue. When a warm melted paraffin wax is applied to the hands of the alleged shooter, it will cause the pores of the skin to open and exude the particles of gunpowder residue. These particles of gunpowder residue are being extracted by the paraffin cast with the use of melted paraffin wax) and will appear as blue specks, when diphenylamine reagent (DPA for brevity) is added to the cast. It must be noted that the specks are generally located on the area of the thumb and forefingers.


The blue color that appears indicates the reaction of nitrates with diphenylamine reagent. Thus, nitrate from other sources like fertilizers will give the same reaction. Other substances similar to nitrate known as oxidizers will also react with the reagent in the same way. 

However, it must also be noted that the blue specks have the characteristic of “tailing”.

What is the Principle behind the Paraffin test?

While   the   burned   and   partially   burned   particles(gunpowder residue) is deposited on the target and in the barrel of the gun, some of these burned and partially burned particles may escape around the breech of the gun and some may be embedded on the exposed surface of the hand/s of the person discharging the firearm. 

Thus, the presence of these residues can be detected by way of paraffin examination.

Paraffin casting of the alleged shooter shall only be done within seventy-two  (72) hours from the time of the alleged shooting incident.  No person shall be subjected to paraffin casting after the lapse of the specified period.

Embalmed cadavers who allegedly discharged a firearm shall no longer be subjected to paraffin examination because of the impossibility of extracting the gunpowder nitrates from the former’s hands.

Paraffin wax (M.P. 38-40 C)

Different names of this test:

Lunge’s test

Diphenylamine test

Dermal nitrate test

Gonzales test - named after the one who improved the test

Question:   Is there any means of removing these nitrates from the hands? How long will they stay in the pores?

Answer: None. Ordinary washing will not remove the nitrates from the pores of the skin. Usually, gunpowder nitrates that are embedded in the skin stay for 72 hours. That is why paraffin casting should be conducted within the specified period.

Substances giving false positive results:

1. fertilizers

2. explosives

3. tobacco

4. urine

5. certain cosmetics

6. food samples

7. cigarette

Question: Will these substances not give positive results for the paraffin test?

Answer: If the hands of the subject person are contaminated with nitrates other than from gunpowder, one will expect to find smudges or just a smear of blue color or a conglomeration of blue specks. But nitrates from gunpowder appear as blue specks with tailings because these particles were embedded into the hands with force.

Question: Is the paraffin test result conclusive evidence? Why?

Answer: No. It is just corroborative evidence that intends to support the testimony of eyewitnesses, There are instances wherein a person who actually discharged a firearm would still give a negative result to the paraffin test because of several factors.

Question: What are these factors?


1. Types of caliber of ammunition

2. Use of gloves

3. Length of the barrel

4. Age of the gun/efficiency of the mechanism

5. Direction of firing

6. Wind direction and velocity

7. Humidity/percentage moisture in air

8. When 72 hours had already lapsed(3 days)

False Positive result

1. Contamination or transfer of gunshot residue (GSR)to the body by mishandling, or when the body is heavily contaminated by GSR from a previous shooting.

2. Washing of hands where samples are collected 

3. Type of ammunition such as rifle and shotgun.

Length of the barrel. 

A weapon with a 2-inch barrel will deposit residue over a larger area than a weapon with a 5-inch barrel (even if they are discharged from the same distance with the same type of ammunition). In a longer barrel, the hand is farther away from the muzzle end of the gun. It takes a bullet to travel in more time, thus using up/burning up more, if not all, of the nitrates. In a short barrel, the bullet travels through the barrel in less time leaving behind a greater amount of unburned particles.

Age of the gun/efficiency of the mechanism. 

Complete combustion or the conversion of all nitrates into its end product(CO, CO,N,O,-OH) is more likely to occur in a new weapon compared to an old one. Besides, leakage of gunpowder is more likely to happen in the old weapon where the breech mechanism is no longer tightly fitted.

Direction of firing.   

More powder residues will be obtained when the gun is discharged pointing upward than downward. Gunpowder residues have weight and will naturally fall down because of gravity.

Wind direction and velocity.  

In high velocity (strong wind), the powder residues will be blown in the direction of the wind. One is more likely to be positive for gunpowder nitrates if there is no wind, or the wind direction is towards the shooter.

Humidity/percentage moisture in the air. 

Humidity lessens the extent of combustion yielding more gunpowder nitrates.

False Positive reaction - a smear of blue color or a conglomeration of blue specks on both dorsal and palm aspects of the hand.

Failure to find traces of nitrate on the hand of the person does not prove that he did not fire a gun. However, it is submitted that the paraffin test has some value due to the psychological effect on the persons whose hands were found positive. Also, the finding of actual traces of gunpowder nitrates on the hand/s of the person does not conclusively determine or establish that he has discharged a gun. It is possible that the GPR particle may have been blown on the hand directly from the barrel of the gun being discharged by another person.

Gunpowder Residue Test on Firearms

The diphenylamine reagent is also applied to cotton swabbing of the barrel and chambers of the gun to determine if the firearm was discharged. A deep blue color resulting from the reaction of nitrates with the reagent indicates the presence of gunpowder residue.

Gunshot Range (GSR) Determination (Also known as gunshot distance determination)

When a firearm is discharged, gunpowder residue may also be deposited on the clothing of the victim. The size and density of the pattern of gunpowder residue found on the clothing are the main factors considered in determining the approximate distance of the shooter to the victim. As the distance to the victim increases, the size of the pattern expands while density decreases and vice-versa.

Distance determination - the method of determining the distance between the firearm and the target. This is usually based on the distance of the powder patterns or the spread of the shot pattern.

Importance of Distance Determination

1. In connection to self-defense pleas

2. In the distinction between murder and suicide.  It is possible to state with certainty the distance of the gun from the target by means of the patterns and residues left on the target. Not only the type of gun, but also the condition and type of ammunition that will affect this pattern.  

In ascertaining the gunshot range (GSR) the examiner should note and observe the following:

1. Entrance and Exit holes

2. Powder residue pattern (Burning, singeing, smudging, tattooing - a  black coarsely peppered pattern)

Entrance and Exit holes:

The entrance hole contains gunpowder residue (bullet wipe residue) and it is slightly burned.

The diameter of the entrance hole is smaller than the exit hole.

The exit hole is frayed outward while the entrance hole is inward.

Other Entrance hole characteristics:

a. Angled bullet entrance hole has an elongated hole.

b. Contact fires have uneven margins but all entrance holes typically have even margins.

c. Grazing bullet hole (several small holes created from a folded garment)

Classification of gunshot distance

- Burning (direct)

- Singeing (1 to 2 inches)

- Smudging (2 to 8 inches)

- Tattooing (8 to 18 inches)

The distance of the muzzle of the gun to the target is classified into three (3):

1. Direct contact

2. 2 inches to 36 inches away

3. 36 inches away or more

Characteristics of Gunshot Wounds

a. Direct/Contact wounds

The principal damage is more visible due to the flame and the muzzle blast than to the penetration of bullet. The following observations may be noted:

1. Gaping hole where fabric is badly torn

2. Blackened area surrounding the bullet hole

3. The presence of partially burned powder residues around the entrance hole

b. Wounds inflicted at a Distance from 2-36 inches:

If the gun is discharged closely to the body of the victim, two (2) types of discoloration will be observed around the hole of the entrance namely:  

(1) smudging and   

(2) powder tattooing (black coarsely peppered pattern).

Smudging is produced when the gun is held from about 2 inches to a maximum of 8 inches. The smoke and soot from the burned pores are deposited around the hole of the entrance producing a dirty appearance.

The size of the smudge depends upon the following: 

A. Length of the barrel: 

A weapon with a 2-inch barrel will deposit residue over a larger area than a weapon with a 5-inch barrel (even if they are fired from a distance with the same type of ammunition). In a longer barrel, the hand is farther away from the muzzle end of the gun. It takes a bullet to travel in more time, thus, using up/burning up more, if not all, of the nitrates. In a short barrel, the bullet travels through the barrel in less time, leaving behind more unburned particles.

B. Age of the gun/efficiency of the mechanism.

Complete combustion or the conversion of all nitrates into it send product is more likely to occur in a new weapon compared to an old one. Besides, leakage of gunpowder is more likely to happen in the old weapon where the breech mechanism is no longer tightly fitted.

C. Direction of Firing.    

More powder residues will be obtained when the gun is fired upward rather than downward. Gunpowder residues have weight and will naturally fall down because of gravity.

D. Wind Direction and Velocity.    

In high velocity (strong wind), the powder residues will be blown in the direction of the wind. One is more likely to be positive for gunpowder nitrates if there is no wind, or the direction is away from the body.

E. Humidity/percentage moisture in air. 

Humidity lessens the extent of combustion yielding more gunpowder nitrates.

Powder tattooing produces a black coarsely peppered pattern. Individual specks of tattooing around the hole are visible to the naked eye.

The area of blackening around the perforation will be found to diminish in size as the muzzle of the gun is held further away from the target.

Take note that the size of the area of powder tattooing will also depend on the following:

- Caliber

- Powder charge

- Distance of firing

c. Wounds inflicted at a Distance of more than 36 inches:

-  Powder tattooing is seldom present

-  Nitrates found will not be sufficient for GSR


Methods used to determine the probable time the firearm has been discharged.

a. Lucas test

A characteristic smell that decreases in intensity with the lapse of time is present immediately after firing but even after several weeks, some slight smell remains.

b. Odor (Hydrogen Sulfide) 

This is another product resulting from the combustion of gunpowder which is present in the gaseous state. This compound can be detected using a lead acetate paper test.

If the breech of the gun is kept closed, this persists between 2-3 hours.

Sulfide - the greater part disappears in about 4-5 hours but frequently a trace remains for a longer time, the longest period being 10 hours.

c. Odor of the Barrel (rusting)

As a rule, no rust can be detected inside the barrel of a firearm if such firearm has not been discharged. But if the firearm has been discharged, iron salts are formed and can be detected inside the barrel. These iron salts are soon oxidized resulting in the formation of rust. The formation of rust is affected by the humidity of the air so in the interpretation of the result, this factor must always be considered.

d. Presence of Nitrates (by cotton swabbing method)

Nitrates diminish after a lapse of time.  Nitrates can be detected by swabbing a portion of residue in a barrel and mixing the residue with Diphenylamine solution (DPA).

e. Dermal Nitrate test

The test is designed to determine the presence of gunpowder nitrates on the hands of the alleged shooter.

Distance from which the gun has been discharged 


a. In connection with self-defense 

b. In the distinction between murder and suicide. It can be stated with certainty the distance of the gun from the target by way of patterns of residues left on the victim.

Scorching or Singeing

If a firearm was discharged very close to the target as in a case of alleged suicide and sometimes in murder, burns or scorches may result. This resulting reaction is caused by a flame that emerges from the muzzle and travels only a short distance from it. This distance will vary with the length of the barrel, the size of the powder charge, and the degree to which the bullet fills the barrel. The presence of scorch is a proof that the firearm was discharged a few inches away from the target. Scorching is very rare if the victim was shot 3 inches or more away from the muzzle.

Other Methods of Examination

The following are the sophisticated instruments used to determine the gunshot range residue (GSR):

AAS - Atomic Absorption Spectrophotometer

NAA - Neutron Activation Analysis

SEM-EDX - Scanning Electron Microscope with Energy Dispersive X-ray Analysis

ICP-MS - Inductively coupled plasma with Mass Spectrophotometry


The following are the guidelines for the proper preservation and safekeeping of evidence:

1. A proper chain of custody shall always be observed.

2. All examined pieces of evidence (drugs and other paraphernalia, explosives, firearms, etc.) shall be personally turned over by the examiner on the case to the evidence custodian. The latter, in turn, shall execute its documentation by recording all received as well as released evidence for court presentation. No examiners shall keep in their possession evidence once examined.

3. Evidence shall be properly placed in suitable dry containers for proper preservation and shall be placed inside the concrete evidence room.

Firearms evidence shall be kept in a separate evidence room specially designed for the purpose. However, hazardous evidence such as explosives and other inflammable evidence is photographed after examination with its corresponding case number before turning it over to the Explosive Ordnance Disposal Unit (EODU) with proper receipt for safekeeping or proper disposal.

4. Clothing removed from the victim should be cautiously and carefully handled to prevent powder residues from becoming dislodged.

5. Do not wad the specimen or pack it loosely for shipment.

6 Secure the area to be tested between two layers of heavy cardboard fastened together tightly to prevent the specimen from becoming postlude about in transit.

7. Each specimen should be wrapped tightly and marked.

8. Clothing heavily smeared with blood should be dried thoroughly before packing.

9. The gun recovered from the scene of the crime and the ammunition available should be preserved.

10. A person suspected to have discharged a firearm should be subjected to a paraffin test. (Cover his hands with paper bags to avoid contamination). Examination must be performed immediately and in no case should it be postponed 72 hours after the shooting.


Body fluid and seminal stains are important evidence. Whether they are bloodstains or seminal stains, they can be employed to determine whether a person is involved in a crime or not. The succeeding paragraphs provide for the proper collection and preservation of blood, saliva, semen, and urine, and the standard for comparison.

1. Blood

It is a must that before collecting bloodstains, a precise description of the extent and pattern of blood spatters should be made. This means that close-up scaled photographs of bloodstains should be done.

If materials with bloodstains are sent to the laboratory, the following procedures should be complied.

a. Air-dry the material on clean paper.

b. When dried, put the material inside a paper bag, Mark the bag with initials, the date and an exhibit number before fastening it. Do not bag items if they are not thoroughly dried.

c. If the material has to be folded, cover the stained area with clean paper. Avoid folding across the stained area.

d. Bloodstained materials should be packaged individually.

e. Collect a comparison standard. The comparison standard is 5cc of blood each taken from the victim and the suspect which are placed in separate vials. A qualified physician is tasked with extracting the blood. The vials are marked with the donor’s name, doctor’s name, date, exhibit number, and other pertinent information.

2. Saliva

a. Air-dry the material on clean paper.

b. When dried, put the material inside a paper bag. Mark the bag with initials, the date, and an exhibit number before fastening. Do not bag items if they are not thoroughly dried.

c. If the material has to be folded, cover the stained area with clean paper. Avoid folding across the stained area.

d. Materials stained with saliva should be packed individually.

e. Collect a comparison standard. The comparison standard is a cotton swab each from the victim’s and the suspect’s mouths.  The swabs are dried and packed separately in paper envelopes. The envelopes are marked with your initials, the donor’s name, the date, the exhibit number, and other pertinent information.

3. Semen

a. Air-dry the material on clean paper.

b. When dried, put the material inside a paper bag. Mark the bag with your initials, the date, and an exhibit number before fastening it. Do not bag items if they are not thoroughly dried.

c. If the material has to be folded, cover the stained area with clean paper. Avoid folding across the stained area.

d. Materials/objects stained with semen should be packed individually.

e. Collect a comparison standard. Get blood and saliva samples following steps 1 and 2.

4. Sweat

Obtain sweat evidence following the steps shown in 3.

5. Urine

Obtain urine evidence following the steps shown in 3.


Latent impressions, regardless of the area of the ridges present, are of the greatest importance to the criminal investigator as their identification may solve the crime and result in the successful prosecution of the subject. Consequently, every effort should be made to preserve and identify them.

It is imperative that fingerprints hidden on no-porous surfaces should be collected immediately and sent to the laboratory since they disintegrate rapidly. When packaging fingerprints, be sure that they are shielded from smudging or deterioration. The succeeding paragraphs will show how fingerprints from non-porous and absorbent surfaces should be gathered and preserved.

1. On Absorbent Materials

a. Put the absorbent material in a plastic bag. Mark the bag with initials, the date, and an exhibit number.

b. Do not directly handle the material with your fingers. Wear a pair of light cloth gloves. Handle an object only by its edges or surfaces, insofar as it is necessary.

c. Avoid processing the fingerprints on absorbent surfaces unless you are trained to perform such a function.

d. Collect standard fingerprints that were properly and legibly taken for comparison.

Lifting Latent prints

a. Get a piece of lifting tape from the roll without cutting. Do not jerk, but pull slowly and gradually, not straight out from the roll but back and downward.

b. Hold the roll in one hand and the tape in the other. Place the end of the tape about ½ inch in front of the print and firmly press the tape evenly over the print by sliding your thumb over it.

c. Remove the tape from the surface by pulling slowly until the tape is almost entirely clear from the surface.

d. Cut off the section used and mount the lifted print on a Crime Scene Evidence Logbook.

e. During the entire operation, never touch the gummed side of the tape.

f. Mark fingerprint evidence collected properly with your initials, the date, and location, and have it initialed by at least two witnesses.

g. Collect standard fingerprints which were properly and legibly taken for comparison.

2. On Soft Surfaces 

a. Be extra careful when extracting fingerprint impressions on soft surfaces such as putty. Permit as much excess material surrounding the fingerprint as possible.

b. Paste the material with the fingerprints on a  stiff cardboard surface. Mark the cardboard surface with your initials, the date, and an exhibit number.

c. Tape a paper cup or glass baby food jar on the evidence for protection. Do not touch the fingerprint.

d. Collect a comparison standard. Submit the tape containing the fingerprint impressions to the laboratory in the condition when it was found.

3. On Skin

a. Fingerprints may be found on the victim’s skin especially if the suspect held him/her. Collect the prints immediately since fingerprints on the skin deteriorate rapidly. When extracting the prints, use methods like dusting, chemical, electronic or photographic techniques. Avoid washing the skin area before processing the fingerprints.

b. Collect a comparison standard. Gather and identify the fingerprints of the suspect, the victim, and those who touched an object under investigation. Put the fingerprint evidence in an envelope and fasten it. Mark the envelope with your initials, the date, and an exhibit number.


Bullets and cartridges have the unique markings of the firearm from which they were discharged. In addition, firearms leave a visible residue on the shooter’s hands. The succeeding paragraphs provide for the proper collection and preservation of the gunshot residue, firearms, serial numbered items, weapons, spent bullets, and spent cartridges.

1. Gunshot Residue

a. Wash your hands or wear a pair of gloves.

b. Get swabs of the back of the suspect’s left and right hand using cotton swabs moistened with 5 percent nitric acid. Do the same for the suspect’s right and left-hand palm areas. Put the swabs in a plastic bag and mark them with your initials, the date, and an exhibit number.

c. Get swabs of the right and left facial cheek areas if a rifle or shotgun is involved.

d. Do not attempt to collect swabs if a .22 caliber was involved; if more than six hours have lapsed; or if the suspect has washed his hands.

e. Make a control swab by wetting a cotton swab with dilute acid. Then put the swab inside a plastic bag marked as “Control swab”.

f. Get a swab of the interior of a spent casing using water, instead of acid. Put the swab in plastic bag marked as “casing”.

g. Put clothing evidence intended for gunshot residue testing inside a plastic bag. Mark the bag with your initials, the date, and an exhibit number.

h. Send the firearm to the laboratory to determine the distance from the bullet hole to the firearm muzzle. If the ammunition is available, send it with the weapon.

2. Small Firearms

a. Photograph the weapon before conducting the examination.

b. Dust the weapon for fingerprints.

c. Remove magazines from automatic loading weapons.

d. Do not operate the mechanism except to unload.

e. Sketch the relative position of the spent casings and live rounds with respect to the barrel.

f. Affix an identification tag to the weapon which will contain a brief description of the firearm, make, model type caliber, or gauge destination serial number, your initials, the date, and an exhibit number.

g. Scratch initials or marks of identification on the side of the frame received back strap, bangle, etc.

h. Do not use “X” to mark stocks, or side plates that can be readily removed or replaced.

i. Record the absence or presence of a round in the chamber. Dust the outer surface of the clip for prints. Put the clip in an envelope then mark.

j. Put the weapon in a plastic bag or paper bag. Mark the bag with your initials, the date, and an exhibit number.

k. Do not send a loaded firearm through the mail.

3. Serial Numbers

a. If the serial number has been erased put an identifying mark on the weapon.

b. Attach an identification tag to the weapon with your initials, the date, and an exhibit number.

c. Put the weapon in a paper or plastic bag.

d. Do not attempt to retrieve the serial number using acid-etch solutions.

4. Shoulder Weapons

a. Photograph the weapon before conducting the examination.

b. Dust the weapon for concealed prints.

c. Do not clean or fire.

d. Record the absence or presence of a round in the chamber.

e. Attach an evidence tag to the weapon with the weapon’s description and serial number.

f. Dust the outer surface of the clip for hidden fingerprints.

g. Put the clip in an envelope and mark.

h. Put the unloaded weapon in a wooden or rigid cardboard box and fasten it. Mark the box with your initials, the date, and an exhibit number.

5. Fired Bullets

a. Photograph the bullets before conducting the examination.

b. Extract the used bullet from the object excluding the material around it.

c. Do not wash or clean.

d. Cover the bullet with cotton then place it in an unbreakable container. Pack the bullets separately.

e. Mark the container with your initials, the date, and an exhibit number.

6. Fired Cartridge Cases

a. Photograph the fired metallic cartridge case before conducting the examination.

b. Do not mutilate, scratch, or nick the head of the shell.

c. If recovered in revolver cylinder mark chambers to correspond with shell designation.

d. Note as to mark of identification used. 

e. Sketch showing the relative position of shells if recovered on floor, or sheet.

f. Transmit the information to the laboratory. Scratch the initial or mark of identification near the mouth of the shell, preferably inside the mouth.

g. Do not scratch, mutilate the head, or read the portion of the cartridge case.

h. Roll individually on paper.

i. Place a rubber band around the paper.

j. Place wrapped cartridges in a heavy paper envelope.

k. Forward to the laboratory. Mark the bag with your initials, the date, and an exhibit number.

7. Fired Paper Shot Shells

a. Photograph the fired paper shot shells before conducting the examination.

b. Do not mutilate, scratch, or nick the head of the shell.

c. Note as to mark of identification used.

d. Sketch showing the relative position of shells when recovered on the floor or streets.

e. Transmit the information to the laboratory.

f. With ink or an indelible pencil, mark the inside of shells using the initials of the person recovering.

g. Do not scratch, nick, or mutilate the brass head of the shell.

h. Roll individually on paper.

i. Place wrapped cartridges in a heavy paper envelope.

j. Forward to a laboratory. Mark the bag with your initials, the date, and an exhibit number.

8. Shot Pellets

a.  Photograph the shot pellets before conducting the examination.

b.  Recover as many as possible. Do not mutilate in removal.

c.  Source the position of recovered pellets.

d.  Record the number and send it to the laboratory.

e.  Note mark of identification used on a seal.

f.  Seal container-marking seal with a mark of identification on the gum label seal on the envelope.

g.  Use a pillbox as the shipping container.

h.  Place the box in the envelope, and seal the envelope.

i.  Indicate the source of pellets on the envelope.

j.  Forward to the laboratory. Mark the bag with your initials, the date, and an exhibit number.

9. Shot Wads

a. Photograph the shot wads before conducting the examination.

b. Recover as many as possible.

c. Recover the source of the wads.

d. Transmit the information to the laboratory.

e. Make notes on the mark of identification used.

f. Using ink or an indelible pencil, inscribe the initials of the person recovering or mark identification.

g. Do not use “X”, place in a paper envelope, sealing for transmission to the laboratory.

h. Place in a paper envelope indicating the source on the envelope.

i. Forward to laboratory. Mark the bag with your initials, the date, and an exhibit number.

j. Gather the spent wads and record their locations. Put them separately in paper envelopes.

k. Mark the envelope with the required identification.

1. Liquids

a. Gather a minimum of one pint of the liquid using a leakproof container.

b. Fasten the container with adhesive tape and mark with your initials, the date and exhibit number.

c. Mark glass containers with “fragile”.

d. Collect a comparison standard.

2. Plant Materials

a. Air dry samples by putting it on a piece of paper for 24 hours.

b. When thoroughly dried, put the evidence in a pillbox or a vial and fasten it with tape.

c. Pack each sample separately.

d. Weigh the contents.

e. Mark the container with your initials, the date, and the exhibit number.

f. Collect a comparison standard.

3. Powder or Solids

a. Put in a container such as a pillbox or a vial.

b. Weigh the contents.

c. Fasten the container and mark with your initials, the date, and an exhibit number.

d. Refrigerate the evidence if required. Do not attempt to add preservatives to solid food samples.

e. Collect a comparison standard.

4. Tablets and Capsules

a. Put the evidence in a plastic vial or a pillbox.

b. Record the contents.

c. Fasten the container and mark with your initials, the date, and an exhibit number.

d. Collect a comparison standard. Search the refrigerator or cupboard for similar materials, which are marked. Avoid removing the samples from their original containers. Put them in sterile, clean containers and refrigerate to inhibit the growth of bacteria. Similarly, comparison standards for drugs are collected following the same procedure.  Do not mix specimens in a single bag even if they were found close to each other or even if they are similar in appearance.


Explosive, Defined.

Explosive is any substance that may cause an explosion by its sudden decomposition or combustion.

It is any chemical compound or mixture that under the influence of heat, pressure, friction, or shock, undergoes a sudden chemical change or decomposition.


I. According to the Velocity of the Reaction involved

A. Low explosives 

These are low-burning and used mainly as propellants like black and smokeless powder

B. Primary and initiating explosive 

This kind of explosive is extremely sensitive to detonation by heat, shock, friction, and impact. It detonates without burning, like lead oxide and mercury fulminate. This is used primarily to start an explosion.

Example: Initiators, blasting caps, shock primer, and stable

C. High explosives

These explosives have very fast or high detonating rates like dynamites, TNT, and Cyclonite (RDX).

II. According to their Chemical structure

a. Organic explosives

b. Inorganic explosives

A. Organic explosives - Nitro-containing organic compound

B. Inorganic explosives – These are salt-containing explosives

III. According to their application or design

a. Military explosives

b. Industrial explosives

Implosion is a similar phenomenon except that the energy released is initially directed inward.

Types of Explosions

a. Mechanical explosion - it is a sudden breaking apart, shattering, or bursting into pieces by internal pressure, such as those caused by the expansion of gas producing high pressure beyond the capacity of the container. Also known as pressure explosion.

b. Atomic explosion - resulting from atomic transformations.

c. Chemical explosion - a source of explosion wherein the source of energy comes from an explosive substance such as gunpowder produced through the extremely rapid transformation of the unstable substances accompanied by the formation of heat.


What evidence to collect

1. Formation of saucer-like crater

2. Presence of fragments and furrow lines (striation marks) ripped through grasses by flying fragments

3. Blast, suction, and fragment damage to nearby structures and vegetation

4. Characteristic smell of burned explosives closest to the crater

5. Blackening of the earth in the crater (carbon deposit)


Fire, defined.

Fire is a chemical reaction (rapid oxidation) that produces physical effects with the evolution of heat and light. This reaction is called combustion.

Fire Investigation is the comprehensive analytical approach to understanding the fundamental properties of fire by determining the chemistry of fires, fuels, and combustion. It is advantageous for an investigator and lawyer on the case if they have at least basic knowledge about the fire.

Classification of Fire Investigation

1. Natural

2. Accidental

3. Unknown origin

4. Suspicious

5. Incendiary (obvious arson)

Incendiary fire

This is the largest and most obvious fire investigated. The primordial intent is to destroy the property/ies of another.

Arson Investigation

Under the law, arson is the malicious burning of a dwelling, house, or building of another. In all fires, there must be a cause before an effect is produced. This cause is known as combustion. Combustion is the effect of certain causes and if these causes are not present, there can be no combustion, spontaneous or otherwise.

The assistance of a Forensic expert plays an important role in arson investigation.

Technical Aspects of Arson Cases

Burning or combustion is the rapid oxidation of substances accompanied by the generation of heat and light. Burning occurs only when three (3) essential ingredients are present: fuel, oxygen, and heat. Obviously, to create a fire, there must be combustible materials. It may be solid, liquid, or gas. Strictly speaking, only gases burn.

The solids and liquids must be heated to liberate flammable gases. The gases in turn must rise to the proper temperature before ignition occurs. Hence, there must be a presence of combustible materials to burn and a source of heat to raise the temperature of the fuel to the kindling point.

Finally, there must be a supply of oxygen since burning is a process of oxidation. Oxygen may be supplied from the air or from oxidizing agents.


Combustion, defined.

Combustion is a burning reaction in which a substance combines with a gas. Heat and light are usually accompanied by combustion reactions and most of these reactions involve oxygen. 

Example: Hydrogen combined with oxygen will undergo rapid oxidation and produce water and heat.

Two types of Combustion

1. Flaming - destructive, gaseous combustion where both the fuel and oxidizer are gases. Flaming fire is achieved when gas or vapor is continuously burning.

2. Glowing - absence of fire but presence of very hot materials on the surface of which combustion is proceeding.

Two kinds of Combustion

a. Complete combustion - all of the reactants are consumed

b. Incomplete combustion - only some parts of the reactant are consumed

Matter - elements, and compounds: composed of atoms combined forming molecules

Air – composed of 21% oxygen and 75% Nitrogen

Oxidation - is a combination of elements and compounds with oxygen-producing stable substances. Those compounds and elements that combine with oxygen and produce fire are called flammable substances and the process is called combustion.

Pyrolisis - comes from the Greek words pyro (fire) and lysis (decompose); a process of decomposition of material to simpler compounds brought about by heat from a fire.

Flame - is a gaseous reaction where the plume of hot gases rises by convection when air and its oxygen is maintained by solid (soot) or liquid (aerosol) in a closed room.


- If oxygen falls below 15%, the combustion rate decreases.

- If the temperature reaches 900-1000 degrees C, post-flashover room fires in which oxygen concentration is only 5-8%.

- If 0-5% and the temperature reaches 1000 degree C - flaming hot

Laboratory Examination

1. Color test using “Sudan Black”.

In this method of examination, the accelerants are allowed to evaporate and the vapors are reacted with this chemical until the pink color of the solution appears which indicates the presence of any accelerant.

2. Confirmatory examination: Gas chromatography with Headspace 

This analytical method is used to detect the specific volatile accelerants by comparing it with known standards such as kerosene, gasoline, etc.


A tool is an instrument or object capable of making a mark on another object. 

A tool mark is defined as any impression, cut, scratch, gouge, abrasion, or any other marking left on an object by another hard object or instrument. A tool mark may be classified as a negative impression, as an abrasion or friction-type mark, or as a combination of the two.

Negative impression - is made when a tool is pressed against or into a receiving surface. This type of mark is usually made when a crowbar is used to pry open a door or a window.

An abrasion or friction mark - is made when a tool cuts into or slides across a surface. This type of mark may be made by a pair of pliers, a bolt cutter, knife, ax, saw, drill, plane, or a die used in the manufacture of wire.


Combination mark - is made, for example, when a crowbar is forcefully inserted into the space between a door and the door facing and pressure is applied to the handle of the tool to force the door open. The forceful insertion of the crowbar produces an abrasion or friction mark and the levering action produces a negative impression.

Why are tool marks important in the crime scene investigation?

Tool marks are important in crime scene investigation because you can tell what kind of tool was used, and by that, you can see if the suspect’s tools match the tool mark.


Glass, defined.

Glass is an inorganic substance in a condition that is continuous with, and analogous to, the liquid state of that substance, but which, as the result of a reversible change in viscosity is, for all practical purposes, rigid.

Glass is normally a fused mixture of silica usually in the form of natural sand and two or more alkaline bases such as soda, lime, or potash. 

Properties of Glass

Glass fractures

Glass fractures may be caused by excessive exposure to heat or caused by impact of a blunt instrument or object, or caused by projectiles.

Types of Glass fracture:

1. Radial Fractures - primary fracture resembles the spokes of a wheel where the radiating rod originates at a common point. When glass breaks, the lines that radiate from the hole are caused by the glass bending away from the point of impact. The radial fractures originate on the opposite side of the glass because this is the surface that is the first to feel the tension. As the front of the glass is pushed in, the opposite side is bent backward. When the limit of glad elasticity is reached, it breaks, with cracking resulting along the radial lines.

2. Concentric Fractures - secondary fractures have the appearance of circles around the point of impact connecting one radiating crack to the other, thus forming triangular pieces of glass. While the radial fractures are forming, triangles are created between the fractures. The newly formed triangle glass between the radial fractures also bends away from the direction of force.  When the limit of elasticity for these triangles is reached, the glass breaks into concentric lines. Concentric fractures originate on the front of the glass.

3. Conchoidal Fractures - A characteristic of glass is that when it breaks, the fracture edges appear shell-like in form - that is, having elevations or depressions in the shape of a shell. The technical name for this condition is “conchoidal” fracture.

1. Entrance and Exit Hole

Point of entry is where the force is being applied and it may produce a smaller hole than the exit. The exit is bigger than the entry for the reason that the force applied to the glass exceeded its desired force. The point of entry has a smooth hole while the exit hole has the characteristic of roughness.

Causes of Glass Fracture

Glass fracture may be due to the following:

1. Due to Natural Means - exhibits plain wavy lines

2. Due to Mechanical Means - exhibits a regular pattern of radial/concentric fracture

Factors to be determined in glass fracture

A. Point of Impact:

Entrance Side

1. Concentric fracture

2. Clear cut edges

3. Absence of depression

4. Absence of flaking

Exit Side

1. Radial Fracture

2. Rugged edges

3. With Depression

4. With flakings

B. Position of the Shooter

1. Perpendicular Shot - exhibits an even distribution of chippings on the exit side of the glass

2. Angle from the Right - heavy flakings or chippings on the left side of the glass

3. Angle from the Left - heavy flakings on the right side of the glass

C. Age of Fracture

1. Fresh Fracture - exhibits a regular pattern of radial/concentric fracture

2. Old Fracture - the presence of a short extension line at the end of the radial fracture


Hair is the outermost covering of the different parts of the body with the exception of the palm of the hand and the sole of the foot.

Through microscopic examination, the forensic examiner will first determine if the hair samples are of animal or human origin. If the hair is of animal origin, a general determination as to species may be made, i.e., cat, dog, horse, cow, carabao, etc.

In the case of human hair, the following can be determined:

1. The race of the person the hair originated from - Negroid, Mongolian, and Caucasian

2. The area of the body surface that the hair originated from - head, face, chest, axilla, and pubic region

3. How hair was removed - naturally or forcibly

4. Whether the hair was cut with a dull or sharp instrument or was crushed or burned

5. Usually examination will not permit conclusive determination of age and sex

Structural Parts of the Hair

A. Inner Aspect:

1.  Cuticle  – the outermost part which is scale-like  in  appearance

2.  Cortex  –   the innermost  portion  that contains  the pigment

3. Medulla – the central canal of the hair

B. Outer Aspect:

1. Tip - the distal end portion of the hair

2. Shaft - portion of the hair above the surface of the skull

3. Root - portion that is embedded in the skin


Ultraviolet examination is a method of scientific examination of evidence using ultraviolet light. Documents, weapons,  chemicals,  minerals, petroleum products, and other items of evidence should be observed routinely under the ultraviolet lamp.

Method of examination

Only suitable ultraviolet lamp and darkroom are necessary for ultraviolet examination. The room should contain adequate table space on which garments and other items to be examined may be spread. The evidence is placed under the ultraviolet lamp.


Questioned fabric may be determined if similar to known fabrics. Positive identification may be made where a questioned piece of fabric may be fitted back into the known fabrics. This type of fabric examination is based on matching broken ends of yarn together.

Generally, fiber matches are not positive evidence and require substantiation with other corroborative evidence.


The examination is similar to fabric examination which generally involves the matching of the ends of pieces of tape used at the scene of a crime with the end of tape on a roll found in the possession of a suspect.

The known sample is compared with the unknown and occasionally, ends may be matched or the manufacturer may be determined.


The paint specimen is examined and compared by using a microscope to determine the color, texture, layer, structure, and any unique characteristics that may serve as points of similarity or dissimilarity.

Paint specimens or scraping is further analyzed using a Quarts Spectrograph to determine and compare the elemental composition of the questioned and standard.


What is the purpose of this test?

Basically, the purpose of this test is to determine whether or not a person is intoxicated with liquor. This test is being conducted to determine the amount of ethyl alcohol present in the blood sample taken from the person suspected to have been intoxicated with alcohol.

Laboratory Examination

Quantitative examination is conducted to determine the amount of ethyl alcohol (or ethanol) present in the blood.

Significance   of   determining   whether   a   person   is intoxicated with alcohol

Intoxication as an alternative circumstance must be taken into consideration as aggravating or mitigating according to the nature and effects of the crime and the other conditions attending its commission.

The intoxication of the offender shall be taken into consideration as a mitigating circumstance when the offender has committed a felony in a state of intoxication, if the same is not habitual or subsequent to the plan to commit said felony; but when the intoxication is habitual or intentional, it shall be considered as an aggravating circumstance.


DNA or Deoxyribonucleic acid is a chemical substance found in all cells whose composition has been passed on from parent to their children. All cells in the body have the same DNA composition except individual egg and sperm cells.

Biological evidence that can be submitted for DNA Analysis:

a) blood and bloodstains

b) semen and seminal stains

c) hairs with follicle or root

d) saliva or buccal swab

e) bones and organs

f) tissues and cells

Cases where DNA Analysis can be of help:

a) Sexual assault

b) Murder

c) Homicide

d) Robbery

e) Hit and run

f) Extortion

g) Paternity case

h) Identification of remains from mass disaster cases and missing persons

How DNA Analysis is used to identify with accuracy the perpetrators of crime

Human tissues such as hair strands, bloodstain, saliva, and other body tissues are often left at the crime scene. By proper collection, preservation, and examination through DNA tests of such pieces of tissues, their owner can be identified.

The Supreme Court, in a recent case, has made a pronouncement on the admissibility of the DNA test result.

Hair strands left by the kidnapper in cases of kidnapping, lairs, bloodstains in clothing associated with murder, saliva stains in cigarette butts, stamps, and envelopes associated with extortion, may all be used to help identify the perpetrators.

How DNA Typing is done

DNA typing is done by first carefully extracting the DNA from the evidentiary samples. The DNA is then analyzed to give a particular pattern. The patterns are compared with that of a known individual to determine a match. In individual identification, the pattern obtained from the evidentiary sample is compared with that of a suspect.


DNA, the genetic “blueprint” of life, is found in every cell of the human body which contains a nucleus. Short for “deoxyribonucleic acid”, DNA is located in chromosomes found within the nucleus of most cells.

Cells that have nuclei, and therefore DNA, are found throughout the human body.

Blood, sperm, hair roots, bone, teeth, organs, muscle, and other tissues all contain DNA which can be tested by forensic scientists.

Body fluids in liquid or dried form, such as saliva and vagina secretions, can also be tested, in as much as these fluids normally contain cells referred to as “epithelial cells”, such as those from the lining of the mouth and vagina.

The types of physiological evidence in criminal cases from which DNA can be extracted and tested are numerous.

Examples include:

a. Blood and semen stains on clothing, weapons, and other surfaces.

b. Swabs taken from victims in sexual assault cases.

c. Hairs with roots attached.

d. Other, less common, sources of DNA evidence include partially decomposed tissue and bone, teeth, and envelopes and postage stamps previously moistened with saliva.



This term is used to describe a broad scope of laboratory tests which used specific antigen and serum antibody reactions.


Blood refers to a highly complex mixture of cells, enzymes, proteins and inorganic substances.

Significance of Blood and Bloodstains

Blood and bloodstains are very vital as evidence in crimes of violence.

Two (2) Main Components of blood

1. Plasma (55% of blood content)-fluid portion of blood composed principally of water.

2. Suspended solid cells (45% of blood content)

a. Red blood cells (erythrocytes)- function to transport oxygen from the lungs to the body tissues and in turn remove carbon dioxide from tissues/organ and transporting it out to the body through lungs. On the surface of these cells, millions   of characteristic proteins were residing which gives blood type characteristic. These proteins were called antigens.

Antigen system 

More than 15 blood antigen systems have been identified. The two most common are the A-B-O system and the Rh system.

b. White blood cells (leukocytes)

c. Platelets


Spot Test - tests for the presence of blood:

a. Benzidine test - presumptive test for the presence of blood.

b. Kastle-Meyer test - using phenolphthalein and hydrogen peroxide forming pink coloration due to the presence of peroxidase   (enzyme) activity of the blood hemoglobin.

c. Luminol test - a spray reagent used to test for the presence of blood even if the blood is not visible under ordinary light. This is viewed under ultraviolet lamp.

d. Takayama test

e. Teichmann test

Tests to determine whether the blood is from Man or Animal

a. Precipitin test - antigen and antibody reaction forming precipitate. This serum will form a precipitin band on the junction between the serum and human blood being tested.

b. Gel diffusion - using agar to test for human blood.

c. Electrophoresis

Blood Clotting

When a protein in blood called fibrin is trapped and enmeshes red blood cells, blood clothing occurs. Removing clotted blood yields a yellowish liquid called serum. This yellow liquid contains certain proteins known as antibodies. The serum that contains antibodies is called antiserum.


Antibody is a protein that destroys or inactivates a specific antigen. Usually denotes a prefix “anti”. By principle, for every antigen, there exists a specific antibody. The reaction of the two is specific. When the two reacts, they immediately combine causing the antibody to attach itself to the cell.

Two (2) antigen-antibody reactions

a. Two different antigen and antibody will not combine. Example: Anti B and A antigen.

b. Link together or agglutinate.


Bloodstain and patterns are useful for interpreting and reconstruction of events that occurred during bleeding.

Characteristic of blood pattern:

a. Surface texture - the harder and less porous the surface, the less spatter results

b. The direction of travel of blood striking an object may be discerned by the stain’s shape. Pointed end of a blood stain always faces its direction of travel.

c. Angle of impact can be determined by measuring the degree of circular distortion of the stain.

d. Origin of blood spatter in a two dimensional configuration can be established by drawing straight lines through the long axis of several individual bloodstains. The intersection or point of convergence of the lines represents the point from which the blood emanated.


Toxicology is a scientific study of poisons, their nature, properties, effects and detection and the treatment in case of poisoning.

Frequently, toxicological examinations are requested in cases of sudden and unexplained deaths. The internal organs and contents obtained during the medico-legal autopsy are the usual specimen submitted, as well as the suspected source of the poison such as food, drinks or medicine. If not fatal, the vomits, blood and urine of the victims are examined. In cases of   mass food poisoning, identification of the poison by the laboratory is important not only in investigation but more in the treatment of the victims. Internal organs and other parts of animals (chicken, dog, cat, etc.), too, are received frequently in connection with complaints of malicious mischief.

Importance of Toxicology

a. To verify if it is a case of poisoning

b. To be able to treat as the occasion demands

c. To forward justice

The reason for the application of Toxicology is to determine the presence of volatile, non-volatile and metallic poisons in cases of alleged poisoning.


Poison is a substance that when introduced into or absorbed by a living organism causes death or injury.

Types of Poisons

1. True poison - is one that still poisons no matter how diluted it is. E.g. Hydrogen Cyanide (HCN)

2. Corrosive poison - is one which by contact with it chemically produces local destruction of tissues. E.g. Nitric acid   (HNO3), mercuric chloride-acid poison used as herbicides.

3. Cumulative poison - is one that increases suddenly in its intensity of action after gradual additions of it.

Ex. digitalis; arsenic


A. Acute Poisoning - one in which there is prompt and marked disturbance of function or death within a shorter period of time and is due to:

1. Taking a strong poison

2. Excessive single dose

3. Several doses, small but frequent

B.  Chronic Poisoning - kind of poisoning in which there is gradual deterioration of functions of tissues and may or may not result in death. It may be produced by:

1. Taking several small doses at long intervals

2. Taking only toxic doses of the drug

Three (3) Major Case Load Areas

1. Police Cases - toxicological aspect of criminal investigations

2. Postmortem cases - analytical studies in support of the medical examiner to determine the cause of death

3. Drug abuse cases - resulting from the illegal use of drugs.

Evidence of Poisoning

1. Circumstantial or moral evidence 

Circumstantial or moral evidence is an evidence deduced from occurrence of facts or circumstances. Ex.- motives for   poisoning, purchasing the poison; keeping the materials used. This is not strong evidence.

2. Symptomatic evidence 

This includes the symptoms observed during the poisoning. This is not conclusive because some diseases may show similar symptoms as those of poisoning

Ex. arsenic poisoning is like cholera; alcoholic coma may stimulate diabetic coma.

3. Chemical evidence 

This is evidence obtained by chemical analysis of the suspected substance or the vomit or secretion of the body. This alone is not reliable because the poison may be decomposed or changed or it may have been replaced after death.

4. Postmortem evidence 

This evidence is obtained from an examination of the tissues and organs after death. There are many poisons, however, that do not produce characteristic findings. Also, the findings may be like those produced by diseases.

5. Experimental evidence 

Experimental evidence is obtained by administering the suspected substance to some living animal and noting the effect or symptoms. This alone is also not conclusive because the tolerance may not be the same as in man.

Methods of Examination

The examination may be divided in two (2) stages, namely, isolation and identification.

1. Isolation

When the submitted specimen is in pure form, the poison must first be isolated. This procedure does not only limit the search to a manageable class of poisons but also reduces the interference from other substances that may occur during the  identification stage. Thus, poison may be classified according to their method of isolation as volatile poisons, non-volatile poisons, and metallic poisons.

a. Volatile poisons - isolated by extraction with alcohol and chloroform

b. Non-volatile poisons - isolated by extraction with organic solvents such as strychnine and other alkaloids

c. Metallic poisons - these are poisons such as arsenic, mercury and lead

d. Other substances requiring special methods of isolation like corrosive acids

2. Identification

1. Preliminary tests

2. Confirmatory tests (modern instruments like the infrared (FT-IR)spectrophotometer and gas chromatograph (GC) can be used in the confirmatory test.

History of Modern Toxicology

Paracelsus - (16th  Century) German Swiss physician/alchemist; first stressed the chemical nature of poison and its action by experimentation. He introduced dose concept.

Prof. Matthieu Orfila - (19th Century) attending physician to Louis XVIII; correlated chemistry of toxins with the biological effects it produces in a poisoned individual.


A. Classification based on Origin

1. Animal/Toxin  –   a   poison   produced   by   livingorganism stimulating antibodies. Usually transferredthrough bites and stings of venomous terrestrial ormarine animals.

2. Vegetable – Poison Ivy and Jimsonweed plants

3. Mineral – Hydrochloric Acid, caustic alkali

4. Microbial – Produced by microscopic organisms Ex.bacteria, fungi 

5. Synthetic - Manufactured by Chemists such as drugs, pesticides as well as chemical purified from natural sources such as   metals from ores and solvents from gasoline.

B. According to chemical properties

1. Volatile Poisons - poisonous compounds that can be isolated using steam distillation and analyzed using Gas Chromatography with thermal head attached on it. Ex: (acidic medium) cyanide, ethanol, methanol, nitrobenzene

2. Non-volatile Poisons - most drugs are non-volatile

3. Anions

4. Metallic

5. Miscellaneous (e.g. Pesticides)

C. Classification based on Physical Form or Property

1. Solid - not well absorbed into the blood, they must be dissolved in aqueous liquid  lining the intestinal tract if ingested or respiratory tract if inhaled.

2. Liquid

3. Gas

4. Vapor

5. Aerosol

D. According to action (Physiological)

1. Irritants - by direct contact, this poison inflames the mucous membrane or the parts it comes in contact with resulting to nausea, vomiting, pain, and diarrhea. 

Ex. Bromine 

True Irritants - Bromine, Chloride, Cotton Oil

2. Corrosives  – by direct contact, chemically produces local destruction of tissues.

Ex: Phenol, HCl,  HNO3 , Caustic Soda (NaOH)

3. Neurotics - those that affect the central nervous system 

a. Cerebral Neurotics: Narcotics - inducing drowsiness, sleep stupor, complete or incomplete insensibility or loss of feeling. 

Ex: alcohol, opium, tobacco

b. Spinal Neurotics: Tetanics - a poison that act on the spinal cord producing spasmodic or continuous contractions of muscles resulting in stiffness of the parts to which they are attached.

Ex: Strychnine, Picrotoxin

c. Cerebrospinal Neurotics

a. Deliriants - are poisons that act on the brain causing disorder of mental functions resulting to confusion of free will.

Ex: cannabis indica, cocaine

b.  Depressants - a substance that depress or retard the physiological action of an organ.

Ex: Antipyrine, lobella

4. Aesthetics/Exhaustive - poisons that cause marked loss of vital or muscular power or general weakness.

Ex: Aconite, KCN, Digitalis

According to their effects on the body/target sites

1. Those which cause local destruction (skin) - phenol, HCl

2. Blood Poisons - Carbon Monoxide (CO), Hydrogen Cyanide (HCN)

3. Nervous Poisons (nervous system)  

4. Cardiac Poisons (Cardiovascular System) - stop the heart beat e.g Digitalis, antipyrine

Solubility of the Drugs

In order for a substance to act as poison, it must be capable of forming solution and readily absorbed by the blood. Barium   Chloride, which is readily soluble, is extremely toxic while Barium Sulfate is not because it is insoluble.


As a rule, the greater the size the greater the effect. This is not always true. Arsenic in large doses irritates the stomach causing vomiting and prompt ejection of the poison so that few or no symptoms result. In small doses absorption occurs and produces fatal effect.

The Physical State or Form of Poison 

A poison is more rapidly absorbed when it is in gaseous state than in solid or liquid form. Also the solvent containing the poison exerts a marked effect upon its action. Thus, between alcoholic, watery or oily solution, the first is more rapidly absorbed.


Generally, when a poison is diluted, the absorption is rapid, thus, resulting to intense toxic effects. An exception to this   is in the case of corrosive poisons. Corrosive poisons produce less toxic effect when diluted.

Mode of Administration 

Basically, poison is more rapidly absorbed when injected in the veins than when taken orally. The intravenous route produces more rapid effects.

Association with other Poisons

Association with other kinds of poisons may increasethe toxic effect. For instance, morphine and chloral together has greater effect than alone. 

Also where the blood supply is greater such as in muscles, absorption is more rapid. Hence, absorption is more rapid in muscles than in skin. Food in the stomach may delay absorption or reacts with the poison.

Entrance and Elimination of Poisons

Poison may enter the body through:



Nose and Eyes

Rectum and Vagina 



They may be eliminated by:






Sweat, Saliva and Tears


Posology is a science which deals with the study of the dosage of medicine to be administered within a certain period.


Medicine is any substance which can be administered to correct or alleviate the disease or disordered state of the system.


Dose is the quantity of medicine to be administered at one time.

The dosage concept is important. Whether a drug acts as a therapy or poison, it will depend on the dose. Even water is poisonous if too much is ingested.

Types of Dose

Safe Dose is one that does not cause harmful effects. Sometimes, however, it may be too small to produce the desired effects.

Minimum Dose is the smallest amount of medicine that can produce the desired therapeutic effect without causing harm.

Maximum Dose is the largest amount that will cause no injury but at the same time produce the desired therapeutic effects.

Toxic or Poisonous Dose is one that is harmful both to the healthy and the sick.

Lethal or Fatal Dose is the dose that kills.


Antidote is any agent that neutralizesa poison or otherwise counteracts or opposes its effects.

Physiological antidote, symptomatic (antagonist) is an agent that acts upon the system so as to counteract the effects of the poison. E.g. (chloral for strychnine convulsions)

Emetics - is an agent that causes vomiting.

Cathartic - is an agent that produces intestinal evacuation.

Uses of Cathartics:

1. To remove the compound that is formed by the action of the chemical antidote.

2. To hasten elimination of poison.

Demulcent - is an agent that forms a protective film; soothes and protects the parts where demulcent is applied.

Precipitants - are substances that prevent absorption of poisons by precipitating them and rendering them insoluble.

Causes of Death in Poisoning

1. Cardiac failure

2. Respiratory failure

3. General devitalizing

4. Shock to the nervous system 


Crime Scene, defined.

Crime scene is an area or vicinity of occurrence of physical evidence.

What Constitute a Crime Scene?

The crime scene can be understood to include all areas in which the criminal, any possible victim, and any eye witnesses moved during the time the crime was committed.

In some crimes, however, the crime scene may actually comprise several different sites.

Illustrative case:

One evening, a young girl was forcibly abducted from her bedroom. She was then transported by car to a small hut in an isolated place. Then and there, she was willfully, feloniously and intentionally sexually assaulted.

Subsequently, the abductor shot her to death and then the former carried the body into the woods where he buried it in a shallow grave.

What are the locations in the given example that constitute the crime scene?

1. Bedroom

2. Car

3. Small hut

4. Area around the grave

Crime Scene Investigation, defined.

It is the conduct of processes, more particularly the recognition, search, handling, preservation and documentation of physical evidence to include the identification and interview of witnesses and the arrest of suspect/s at the crime scene.

First Responder

First responder is any police officer who first arrives at the crime scene and shall endeavor to protect and secure the crime scene. The first responder must be able to properly preserve the crime scene in order to get maximum scientifici nformation that will help in the successful prosecution of the perpetrator of the crime.

The first responder must do the following upon arrival at the crime scene:

a. Cordon off the crime scene with whatever available materials like police line, if available, or ropes, straws or human barricade;

b. Evacuate injured persons to the nearest hospital;

c. Prepare to take the “dying declaration” of severely injured person, if any;

d. Prevent entry/exit of persons within the cordonedarea; and

e. Prepare to brief the investigators of the situation upon their arrival.

Crime Scene Analysis or Crime Scene Response

Crime scene analysis or crime scene response is much more than processing (searching) and documenting (notes, photos, sketches), and certainly more than packaging (collecting) and tagging (preserving evidence).

Crime scene analysis is a slow, methodical, systematic, and orderly process of collecting physical evidence based on proper   recognition and collection to be processed in the laboratory by forensic examiner to uncover significant clues from them.

Crime laboratories do not solve crimes; only a thorough and competent investigation conducted by professional police officers  enhances chances for the successful outcome of a criminal investigation. If the investigator cannot recognize or preserve   physical evidence, no sophisticated machine in the laboratory or technical expertise can save the situation.

It must be noted that in the crime scene, proper crime scene processing based on scientific method of investigation must be made for the identification and successful prosecution of the person responsible for the commission of a crime.

The following are the lists of physical evidence which will most likely yield significant results upon examination:

1. Blood, semen and saliva (liquid or dried, animal orhuman)

2. Documents (written and typed) - paper, ink, indented writings, obliterations and burned or charred documents

3. Drugs

4. Explosives (any object that contain an explosive residue)

5. Hairs and Fibers

6. Fingerprints (latent and visible)

7. Firearms and Ammunition

8. Glass particles or fragments that may have been transferred to person or object involved in a crime.

9. Impressions (shoe prints, depressions in soils and other tracks, glove and fabric impression, and bitemark)

Cases Falling Under the SOCO Category

a) Murder

b) Homicide

c) Rape with Homicide

d) Arson

e) Robbery with Homicide

f) Other heinous/sensational cases as directed by higher headquarters and other cases where SOCO assistance is necessary

Composition of SOCO Team

a) Team Leader

b) Driver/Evidence Custodian

c) SOCO Specialists/Technicians

a. Health officer

b. Crime photographer

c. Sketcher/Measurer

d. Forensic chemical officer

Basic SOCO Equipment / Materials

1. Police Line

2. Measuring device e.g. ruler and measuring tape

3. Recording materials e.g. chalk, notebook, sketching and paper pad, pencils, Pentel pens, permanent ink marker, and coupon bond

4. SLR camera with film

5. Video camera

6. Tape recorder

7. Evidence collection kit

8. Compass

9. Searchlight with battery charger

10. Evidence tags/markers

11. First Aid kit 

12. Paper bags (all sizes)

13. Stylus

14. Vernier Caliper

15. Micrometer

16. Paraffin wax

17. SOCO forms and Crime Lab request form

18. Gloves

19. Gauze

20. Fingerprint card

21. Black and White latent lifting card

22. Eraser

23. Stapler with extra staple wire

24. Kit board

SOCO Tools

1. Flashlight

2. Scissors

3. Knife (heavy duty and folding)

4. Rulers and measuring tapes

5. Adjustable wrench

6. Pliers

7. Wire cutter

8. Complete screwdriver set

9. Saw

10. Hammer

11. Ax or hatchet

12. Shovel

13. Fingerprint magnifier

14. Nylon brush

15. Magnet

16. Spatula

17. Box of plaster of Paris for the casting of lifting

18. Goggles

19. Sitting screen

20. Funnel (different sizes)

21. Scalpels

22. Ladder


Basic Equipment

1. Police line

2. Marker

3. Camera with film

4. Evidence collection kit

5. Video camera & tape recorder

6. Measuring device e.g. ruler and measuring tape

7. Flashlights, hand gloves, masks, eye goggles, hair net

8. Recording materials e.g. chalk bond paper, pencil, clipboard, Pentel pens

Evidence Containers

1. Glass vials

2. Absorbent cotton

3. Cardboard boxes

4. Paper bags, plastic bags

5. String tags – large and small

6. Plastic gallons, bottles (small and large)

7. Evidence tape of masking/scotch tape

Approaching the Crime Scene:

Be alert

Make pertinent notes as to possible entry and exit points of the perpetrator.

Crime Scene Investigation Proper

The following  are the procedures in the crime scene investigation:

a. Receipt of briefing and designation of command post 

The Team Leader upon arrival at the crime scene receives the briefing from the first responder and shall immediately designate a command post.

Command Post - is an area that is ideally located adjacent to the crime scene where the CSI evidence custodian stays and receives the pieces of evidence turned over to him for safekeeping by the other evidence collectors.

b. Initiation of Preliminary Survey

The Team Leader makes a general assessment of the scene, takes a cautious walk-through of the crime scene, takes down extensive notes to document important factors, and establishes the evidence most likely to be encountered. He then defines the extent of the search area determines the personnel and equipment needed, and makes specific assignments. From his assessments, he develops a general theory of the crime scene.

c. Preparation of Narrative Report

The Team Leader uses the systematic approach in making a narrative report.

d. Documentation of the Crime Scene

The photographer should begin taking photographs as soon as possible. The taking of photographs of the crime scene must be from general to specific areas. The evidence collectors should not touch or move any evidence where it is originally located until it has been identified, photographed, sketched, measured, and recorded.

e. Crime Scene Sketches

A rough sketch should be prepared indicating the actual measurement of things with scale and proportion observed and oriented to the North Pole. All necessary information should be placed in the sketch.

f. Detailed Search

The search for physical evidence must be done using the accepted methods of search depending upon the actual location to be searched.

g. Collection of Physical Evidence

The competence to recognize and properly collect physical evidence is critical to both solving and prosecuting crimes. The  Team Leader should be informed always of the significant evidence located. It must be noted that the evidence collector should put his initial, location, and date of collection on the item and turn it over to the evidence custodian for documentation and safekeeping. 

h. Conduct of Final Survey

The Team Leader shall make a final review of the crime scene to determine whether or not the processing has been completed.

i. Release of the Crime Scene

The release of the crime scene shall be done if the investigator is satisfied that all pieces of evidence have been recovered. Hence, the investigator must evaluate the items recovered from the results of the interrogation of the suspect/s and the interview of the witnesses. It must be noted that upon formal release of the crime scene to the proper authority, a warrant is already required for his re-entry to the crime scene.

Crime Scene Photography

The purpose of taking photographs of the crime scene is to create an accurate objective visual record of the crime scene before any physical evidence is moved or removed from its original location.

Guidelines for taking photographs of a Crime Scene

During the conduct of the crime scene operation, it is basic that photographs of a crime scene should be taken as soon as possible before the start of note-taking, sketching, and searching for physical evidence.

It must be noted that the photographs should illustrate the original, uncontaminated condition of the crime scene. 

Photographs should be taken of the crime scene only. No investigator or any police personnel should be photographed at the crime scene. The photographs must form an organized sequence and show all relevant locations and objects. The crime scene photographs must progress from general to specific.

Crime Scene Sketches 

Sketches are useful in questioning suspects and witnesses as well as in writing investigative reports.

A rough sketch must be made indicating the actual measurement of things with scale and proportion observed and oriented to the North Pole. All necessary information must be placed in the sketch.

Sketches are excellent companions to photograph. Where photographs provide exact details, sketches give accurate information about the placement of objects and they show relationships and distances between things.


Note-taking must be a constant activity throughout the processing of the crime scene.

Notes must include:

a. Detailed written description of the Crime Scene with locations of physical evidence received.

b. The time when the physical evidence was discovered.

c. The person who discovered and collected the physical evidence.

d. How the evidence was packaged and marked.

e. The disposition of the item when it was collected.


Documentation is made by the crime scene investigator for purposes of future crime scene reconstruction which will help the prosecutor and the judge understand conditions at the crime scene.


The search for physical evidence is done using the accepted methods of search depending on the actual location to be searched.

The crime scene search could only be started after the crime scene had been photographed and sketched.

The primary duty of the SOCO Team Leader upon arrival at the crime scene is to make proper coordination with the investigator-on-case or the officer-in-charge. The purpose of coordination is to secure the approval of the investigator before the SOCO assumes control of the crime scene. The team may proceed with the processing after conducting the general survey and after establishing a common approach path.

As every crime scene is unique, the employment of each method of search depends on the physical nature of the scene and the kind of offense involved. Each approach varies as the situation dictates. For purposes of the scene of crime operation or crime scene processing, the following methods may be employed:


In this method, one searcher is assigned to a quadrant. Then each quadrant is cut into another set of quadrants.


In this method, the area is blocked out in the form of a rectangle. The searcher proceeds slowly at the same pace along a path parallel to one side of the rectangle. When a piece of evidence is found, the finder announces his discovery and the search must stop until the evidence has been cared for. A photographer is called, if necessary. The evidence is collected and tagged and the search proceeds at the given signal. At the end of the rectangle, the searcher turns and proceeds along new lanes as shown in the above illustration.


In this method, the searchers follow each other along the path of a spiral, beginning on the outside and spiraling towards the center.


The grid or double strip method of search is a modification of the strip search method. Here, the rectangle is traversed first parallel to the base and then parallel to the side.


In this method of search, the area is considered to be approximately circular.  The searchers gather at the center and proceed outward along radii or spokes. The procedure should be repeated several times depending on the size of the circle and the number or searchers. One shortcoming of this method is the great increase in the area to be observed as the searcher departs from the center. Another is the possibility of evidence contamination or destruction with the likelihood that the searchers will step on them as they converge at the center. 

Purpose of a Crime Scene Search

a. To systematically look for physical evidence that may prove useful in establishing that a crime has been committed.

b. To determine what method of operation the perpetrator may have used.