Paraffin & Toxicology

Paraffin Test and Gunpowder Residue

The paraffin test is a method used to detect gunshot residue. It aims to determine if a person has recently fired a gun. While it provides corroborative evidence, it is not conclusive on its own.

Other Names for the Paraffin Test

The paraffin test is also known by several other names:

• Lunge's test

• Diphenylamine test

• Dermal nitrate test

• Gonzales test (named after Dr. Gonzalo Iturrios) - to locate/extract the particles of the nitrate

How the Paraffin Test Works

The test is based on the detection of nitrates present in gunpowder residue. When a person fires a gun, tiny particles containing nitrates are deposited on their hands, particularly on the thumb and forefingers.

1. A paraffin cast is made of the subject's hands.

2. This cast extracts the nitrate particles.

3. When diphenylamine (DPA) reagent is added to the cast, the nitrates react to form distinctive tailing deep blue specks.

For optimal results, the cast should be performed within 72 hours (3 days) of the potential gun discharge.

Limitations and False Positives

The paraffin test is not conclusive because:

• A person who fired a gun might still yield a negative result due to various factors.

• Many other substances, known as oxidizers, contain nitrates and will react with the DPA reagent in the same way, leading to false positive results. These include:

• Cigarette ash

• Fertilizer

• Tobacco

• Explosives

• Certain cosmetics

• Urine

• Some food samples

Paraffin Testing ProcedureMaterials

Paraffin wax, cotton, hot plate, a small pot, medicine dropper, forceps, DPA reagent, 2 sheets of long bond paper. Must be height distance between the dropper to the subject's hand.

Instructions

1. Volunteer Preparation: Two volunteers are assigned. One washes hands with plain water, the other with laundry detergent and water.

2. Melt Paraffin: Melt paraffin wax at 37∘C in a small pot on a hot plate.

3. Hand Preparation: Volunteers place their hands on bond paper, which is then labeled with their names and signatures.

4. Prepare Wax: Place cotton in the melted paraffin wax and mix carefully with forceps.

5. Apply Wax (First Layer): Test the wax temperature to ensure it's safe. Apply several drops of melted paraffin wax to both hands of the volunteers. Repeat until both hands are completely covered.

6. Apply Cotton and Wax (Second Layer): Cover the first wax layer with cotton, then apply an additional layer of paraffin wax.

7. Repeat Layering: Repeat the previous step (cotton and wax).

8. Dry Cast: Allow the paraffin cast to dry for 30 minutes.

9. Remove Cast: Slowly remove the casts from the hands. Instruct subjects not to submerge hands in water immediately to prevent injury.

10. Apply Reagent: Place several drops of diphenylamine reagent on both paraffin casts and observe the color reaction.

11. Conclusion: Conclude based on the experiment's findings.

Types of GunpowderBlack Powder

A mixture composed of:

• Carbon or charcoal (15%)

• Sulfur (10%)

• Potassium nitrate (75%)

Smokeless Powder

• Single base: Composed primarily of nitrocellulose.

• Double base: Composed of nitrocellulose, nitroglycerine, and other stabilizers.

Tests for Gunpowder NitratesGunshot Range (GSR) Test

This test analyzes the size and density of gunpowder patterns on clothing to determine the distance between the firer and the victim.

• As distance increases, the pattern size increases, while density decreases.

Neutron Activation Analysis

This advanced technique uses access to a nuclear reactor to determine radiation levels, which can help identify specific elements from gunpowder residue.

Gunpowder Residue Test (GPR)

• Diphenylamine reagent is applied to cotton swabs taken from the barrel and chamber of a suspected firearm.

• A deep blue color indicates the presence of gunpowder residue, suggesting the firearm was recently fired.

Paraffin-Diphenylamine Test

• Uses Lunge's reagent, prepared by dissolving 0.5g of diphenylamine in 100cc of C.P. sulfuric acid and adding 20cc of water (also known as DPA reagent).

• A positive result is indicated by tailing deep blue specks.

Factors Affecting Paraffin Examination Results

Several factors can influence the outcome of a paraffin test:

• Length of the barrel

• Type of caliber of ammunition

• Wind velocity and direction

• Age of the gun / efficiency of its mechanism

• Humidity / percent moisture in the air

• Use of gloves

• Direction of firing

• Passage of time (especially beyond 72 hours)

Guidelines for Estimating Target DistancesContact Less Than 1 Inch from Target

• Heavy concentration of smoke-like vaporous around the bullet's entrance hole.

• If tthe wound is smaller than the bullet, t's an entrance. But, if the wound is bigger than the bullet, it's an exit.

• Scorch marks on loose fibers around the entry hole.

• Presence of a stellate tear pattern around the hole due to muzzle gases blowing back.

Contact 12 to 18 Inches or Less from Target

• A halo of vaporous lead deposit around the bullet hole.

Contact 25 Inches (Closed)

• Scattered specks of unburned and partially burned powder grains, with no accompanying soot. Near the wound

Contact 36 Inches (Tattoing)

• Scattered gunpowder particles, typically from ball powder ammunition. Away from the wound

Contact More Than 3 Feet from Target

• Typically no deposit of any powder residues on the target.

• A "bullet wipe" or dark ring around the perimeter of the bullet hole.

Two Types of DiscolorationTattooing

• The presence of a black, coarsely peppered pattern around the entry wound.

• Caused by partially burned and unburned particles of gunpowder embedded in the skin or clothing.

Smudging

• A dirty, grimy appearance deposited around the entrance hole.

• Caused by soot from burned powder.

What is Gun Residue?

Gun residue, also known as Firearm Discharge Residue (FDR) or Cartridge Discharge Residue (CDR), is composed of:

• Burned and unburned particles from the propellant (gunpowder).

• Particles from the explosive primer.

• Components from the bullet itself.

• Components from the cartridge case.

• Material from the firearm.

Toxicology: The Science of Poisons 🧪

Toxicology is the scientific study of detecting and identifying drugs and poisons within tissues, organs, and body fluids. It encompasses various related fields and concepts:

Key Definitions

• Toxinology: A specialized branch focusing on toxins produced by animals, plants, and microbes.

• Toxin: Naturally occurring poisonous substances created by living organisms.

• Toxic Substances: Synthetic poisonous substances derived from chemicals.

History of Toxicology 📜

Toxicology has evolved significantly over centuries:

• 16th Century: Paracelsus famously stated that "all substances are poison," highlighting the dose-dependent nature of toxicity.

• 1786: Plenck emphasized the crucial need to identify poisons within the body.

• 1821: Mathieu Orfila, a French physician, pioneered the first classification system for poisons.

• 1836: Arsenic was successfully extracted from a cadaver for the first time, with James Marsh performing the inaugural arsenic test.

• 1842: The Reinsch test was developed to detect arsenic and mercury.

• 1850: Methods for testing metals were established, and Stratas-Otto introduced a technique for alkaloid extraction.

• 1910: Dr. Alexander Gettler, a chemistry professor, laid the foundation for forensic toxicology in the United States.

Importance of Toxicology

Toxicology plays a vital role in several areas:

• Verifying Poisoning Cases: Determines if poisoning is the cause of illness or death.

• Guiding Treatment: Provides crucial information for effective medical intervention.

• Forwarding Justice: Serves as a critical tool in legal investigations and forensic science.

Understanding Poisons

A poison is any substance that, when introduced into the body, can cause injury or death.

• Suicide Method: Overdosing on pills is a common method of suicide.

• Painless Death: Some poisons can lead to a relatively painless death.

• Mimicking Diseases: Certain poisons can imitate symptoms of diseases, leading to misdiagnosis or weakening the body, making it susceptible to other illnesses.

Commonly Used PoisonsArsenic (highly toxic chemical)

• Description: A frequently used poison.

• Symptoms: Includes vomiting, diarrhea with blood, and severe stomach discomfort.

Cyanide

• Mechanism: Prevents red blood cells from absorbing sufficient oxygen.

• Result: Leads to "internal shortness of breath."

Types of Poisons

• Corrosive Poisons: Substances that destroy tissues upon contact. Causes irritation

• True Poisons: Natural poisons, such as cyanide found in silver cleaners. Through absorbing

• Cumulative Poisons: Poisons whose effects intensify with gradual accumulation (e.g., arsenic).

Types of Poisoning

• Acute Poisoning: Results from immediate exposure to a poison, often leading to rapid death.

• Chronic Poisoning: Occurs due to gradual exposure, where the effects do not manifest immediately.

Classification of Poison वर्गीकरण

Poisons can be classified based on various characteristics:

Based on Origin

• Animal

• Mineral

• Synthetic

• Microbial

• Vegetable

Based on Chemical Properties

• Metallic: Detected through isolation and extraction using solvent extraction and flame tests (e.g., arsenic exhibits a blue flame).

• Non-Volatile: Analyzed through solvent extraction and confirmed using Fourier Transformed Infrared Spectrophotometer (FT-IR).

• Volatile Poisons: Isolated by distillation, with the distillate analyzed using GC-MS.

• Anions: Detected using qualitative methods of examination for the presence of specific anions.

• Miscellaneous: Other poisons, such as pesticides.

Based on Physical Form

• Solid

• Gas

• Aerosols

• Vapor

• Liquid

Based on Physical Effects

• Irritants: Cause nausea, vomiting, and diarrhea upon contact with sensory organs.

• Corrosives: Strong acids and bases that destroy tissues upon contact.

• Neurotics: Affect the nervous system.

• Spine neurotics: Picrotoxin, cerebrospinal.

• Cerebral neurotics: Alcohol, opium, tobacco.

• Cerebrospinal neurotics: Further classified as deliriants and depressants.

• Aesthetics/Exhaustive: Agents causing exhaustion, marked by loss of vital or muscular power.

• Exito-Motor in Action: Poisons that stimulate motor functions.

• Poisonous and Irrespirable Gases: Gases that are toxic and prevent breathing.

• Contact Poison: Poisons that act upon direct contact.

• Vulnerants: Substances that cause wounds or injuries.

Based on Effects on the Body

• Local destruction on the skin

• Blood poisons

• Nervous poisons

• Cardiac poisons

Based on Chemical Standpoint

• Gaseous Poisons: Poisons in a gaseous state.

• Inorganic Poisons: Corrosive chemicals and metallic salts.

• Organic Poisons: Volatile liquids.

• Miscellaneous Poisons:

• Food poisoning

• Poisonous plants

• Poisonous animals and their poisons

• Biological products

• Ground glass

According to Methods of Isolation

• Volatile Poisons: Isolated by distillation, with or without steam.

• Non-Volatile Poisons: Isolated by extraction with organic solvents.

• Metallic Poisons: Require specific methods.

• Substances Requiring Special Methods of Isolation: Poisons that do not fit into the above categories.

Common Poisons and Their Symptoms 🤒

Site of Action of Poison

Poisons can act in different ways:

• Local Action: Acts directly on the skin, mucous membrane, or application site.

• Remote Action: Acts on distant parts of the body. This can occur:

• By inducing shock.

• By absorption into the blood and transport to target organs.

• By nerve transmission from local parts to nerve centers, then reflected to organs.

• Both Local and Remote: Acts at the application site and other remote parts of the body.

Site of Remote Actions of Different Poisons

• Brain: Narcotics, alcohols, cerebral stimulants like caffeine.

• Spinal Cord: Strychnine.

• Peripheral Nerves: Conium, curare.

• Alimentary Tract: Corrosives.

• Kidneys: Cantharides.

• Salivary Glands: Mercury.

• Liver: Phosphorus.

• Mucous Membrane: Arsenic.

• Heart: Digitalis.

• Blood Vessels: Ergot, nitrates.

• Blood Cells: Snake venom.

Types of Poisoning (Medical & Legal)Medical Point of View

• Acute Poisoning: Immediate and severe effects.

• Sub-acute Poisoning: Effects developing over a short period, less intense than acute but more prolonged.

• Chronic Poisoning: Gradual effects due to prolonged exposure.

Legal Point of View

• Accidental

• Suicidal

• Homicidal

• Undetermined

Treatment of Acute Poisoning 🏥Evacuation of the Stomach

Methods to remove poison from the stomach:

• Stomach Tube: Gastric lavage.

• Administration of Emetics: Substances that induce vomiting.

• Zinc Sulphate (30 grams)

• Ipecacuanha (20-30 grams in 2-6 drachms of wine)

• Mustard and water (one tablespoon in one tumbler of water)

• Salt and water

• Apomorphine (1/10 gr. Hypodermically)

Neutralization of Remaining Poison in the Stomach

• Direct Chemical Reaction:

• Acids neutralize alkalies.

• Alkalies neutralize acids.

• Physiochemical Reaction:

• Silver nitrate is precipitated by common salt.

• Iodine reacts with starch.

• Physical Reaction: Formation of insoluble compounds to prevent absorption.

• Tannic acid precipitates strychnine.

• Egg albumen precipitates mercuric chloride.

Conditions Making Poison Examination Meaningless

• Embalming: Preservative chemicals can interfere with poison detection.

• Putrefaction: Decomposition of the body can alter or destroy evidence of poisons.

Methods of Examining Poisons

• Identification: Involves screening and confirmatory tests to establish the presence of poisons.

• Isolation: The process of obtaining the desired substance in its pure form through techniques like distillation, solvent extraction, and chromatography.

Kinds of Antidotes

• Mechanical Antidotes: Remove poisons from the body without altering their chemical nature.

• Chemical Antidotes: React with poisons to render them harmless.

• Physiological Antidotes: Counteract the effects produced by poisons.

Application of Physiological Antidotes

• Strychnine may be used to stimulate respiration.

• Depression of the heart by aconite may be counteracted by digitalis.

• Blood vessels may be constricted by ergot.

• Morphine, bromides, or barbiturates may be given for poisoning by stimulants.

Eliminating the Poison

The body eliminates poisons through various mechanisms, aided by specific substances:

• Purgatives: Aid in bowel movements to expel poisons.

• Sudorifics: Induce sweating.

• Diuretics: Increase urination.

Encouraging Sweating: Hot baths, warm packing, and apomorphine injections.

Other Elimination Routes:

• Emesis (vomiting)

• Respiration

• Feces

• Urine

• Milk

• Sweat

• Saliva

• Tears

Alcohol Intoxication 🍻

• Source: Primarily ethanol.

• Fermentation: Yields 12%- 15% alcohol.

• Distillation: Concentrates alcohol to 40%- 60%.

• Breathalyzer: Used to detect alcohol intoxication, especially in suspected drunk drivers.

Tolerance and Idiosyncrasy

• Tolerance: A condition where the body requires larger doses of a toxic substance to produce the same effect due to repeated exposure.

• Idiosyncrasy: The opposite of tolerance, where even small amounts of a substance can have a fatal effect on an individual.