Forensic Toxicology and Drug Identification

Vocabulary flashcards covering biological specimen collection, detection windows, presumptive colour reagents, confirmatory instrumentation, and United States drug schedules from the Week 11 Forensic Toxicology lecture.

Forensic Toxicology

The scientific study of drugs and poisons in a forensic context, involving the identification, quantification, and evaluation of substances in biological samples to assess their contribution to death or behavioural effects.

Paracelsus's Principle

The foundational toxicological concept that 'the dose makes the poison,' stating that any substance can potentially be toxic depending on the amount present, in conjunction with individual characteristics and metabolism.

Drug Metabolism

The chemical modification of drugs within the body, typically mediated by enzyme activity, which converts a parent drug into one or more metabolites.

Parent Drug

The original chemical form of a drug prior to undergoing metabolic breakdown or biotransformation in the body.

Metabolite

A distinct chemical substance produced as a result of the metabolic conversion and breakdown of a parent drug within the body.

Quantification

The analytical process of determining the exact amount or concentration of a substance present in a biological or physical specimen.

Identification

The analytical determination of the specific chemical identity or class of a substance present in a specimen.

Toxicity

The intrinsic capacity of a chemical substance to cause harmful, damaging, or lethal effects to an organism.

Blood (Toxicology Specimen)

The specimen of choice for forensic quantification; it indicates relatively recent drug exposure and enables investigators to relate measured drug concentrations directly to intoxication or death.

Urine (Toxicology Specimen)

A biological sample that is easy and rapid to collect before or after death, offering longer detection windows than blood but presenting challenges in estimating exact dosage and timing of use.

Hair (Toxicology Specimen)

A biological specimen cut close to the scalp from the back of the head, growing at approximately $1\,\text{cm}$ per month, used to evaluate historical or chronic drug exposure.

Nail Sampling

A toxicological testing method for chronic exposure; nail keratin is approximately four times thicker than hair and incorporates drugs and metabolites as nails grow.

Saliva (Oral Fluid) Sampling

A non-invasive biological specimen used to detect relatively recent drug exposure; its concentrations can vary widely and do not correspond directly to blood concentrations.

Liver (Toxicology Specimen)

The primary solid organ tissue sampled in post-mortem toxicological examinations, collected from deep within the right lobe to identify accumulated drugs and metabolites.

Vitreous Humour

The clear, colourless, anatomically isolated, and stable fluid of the eyeball, collectable up to four days post-mortem and particularly useful for detecting hydrophilic substances and assessing alcohol concentration.

Lung Sampling

A post-mortem tissue or fluid collection (typically a whole left or right lung or tied-off lung) analysed primarily qualitatively when exposure to gases or volatile compounds is suspected.

Stomach Contents

A post-mortem sample collected completely during suspected oral ingestions or poisonings, where intact pills or tablets are separated to identify the original substance ingested.

Forensic Chemistry

The discipline focused on identifying non-biological unknown chemical evidence recovered from crime scenes, including active ingredients and additives in powders, tablets, and paraphernalia.

Presumptive Test

A preliminary, non-conclusive screening test performed at a crime scene or laboratory to indicate general substance characteristics and narrow down possible drug classes.

Marquis Test

A colour screening test using 2% formaldehyde in sulfuric acid, yielding purple for opiates, orange for amphetamines/methamphetamines, blue-black for MDMA, and fizzing with no colour change for cocaine.

Dillie-Koppanyi Test

A two-step presumptive colour test for barbiturates employing Solution 1 (1% cobalt acetate) and Solution 2 (5% isopropylamine in methanol) to produce a violet-blue colour.

Duquenois-Levine Test

A presumptive test for marijuana utilizing vanillin and acetaldehyde in ethanol, concentrated hydrochloric acid, and chloroform, with a positive result indicated by a purple chloroform layer.

Van Urk Test

A presumptive test for LSD using p-dimethylaminobenzaldehyde in hydrochloric acid and ethyl alcohol, resulting in a dark blue-purple colour reaction.

Scott Test

A three-step presumptive colour screening test for cocaine using cobalt thiocyanate, concentrated hydrochloric acid, and chloroform, resulting in a blue to pink to blue colour sequence.

Microcrystalline Testing

A presumptive analytical technique in which a chemical reagent is added to an unknown substance to observe characteristic microscopic crystal formations.

Ultraviolet (UV) Spectroscopy

A preliminary screening method that measures the characteristic absorption of ultraviolet radiation by a substance to gain chemical structural information.

Gas Chromatography (GC)

An analytical separation technique that dissolves, vaporises, and separates mixtures into individual components displayed as retention peaks on a chromatogram.

Confirmatory Drug Testing

A high-specificity analytical protocol that uses separation and instrumental identification to conclusively establish the identity of a substance against reference standards.

Mass Spectrometry (MS)

A confirmatory analytical method wherein vaporised molecules are fragmented by an electron beam to generate characteristic mass-to-charge ($m/z$) spectral patterns compared against known references.

Infrared (IR) Spectroscopy

A confirmatory instrumental method that measures the vibrational absorption of infrared radiation by chemical bonds, revealing molecular functional groups and structural identity.

Schedule I Controlled Substances

Under the United States scheduling system, drugs defined as having a high potential for abuse and no accepted medicinal use, including heroin, LSD, peyote, and MDMA.

Schedule II Controlled Substances

Drugs defined under the United States system as having a high potential for abuse but accepted, severely restricted medical use, such as cocaine, methamphetamine, methadone, oxycodone, and Ritalin.

Schedule III Controlled Substances

Drugs classified under the United States system as having accepted medical use, a moderate potential for abuse, and low to moderate dependence risk, including barbiturates, steroids, ketamine, and testosterone.

Schedule IV Controlled Substances

Drugs defined under the United States system as widely used medically with a low potential for abuse and low dependency risk, including Xanax, Valium, and other tranquilisers.

Schedule V Controlled Substances

Drugs classified under the United States system as widely accepted for medical use with very low abuse potential, often containing limited narcotics, such as Robitussin, paracetamol, and Lomotil.