Forensic Toxicology and Chemistry

Vocabulary practice flashcards covering core definitions, biological sample matrices, presumptive colorimetric tests, confirmatory instrumental analysis, and drug scheduling classifications from the Forensic Toxicology and Chemistry lecture.

Forensic Toxicology

The scientific study of drugs and poisons, encompassing their identification, quantification, and confirmation in biological specimens or evidence to determine whether their concentration contributed to death or specific behaviours.

Blood (Toxicological Specimen)

The specimen of choice for quantifying substance levels and establishing a direct correlation to intoxication, serving as an indicator of recent drug exposure.

Urine (Toxicological Specimen)

A biological specimen collected pre- and post-mortem that is rapid and easy to obtain, often containing drugs in higher concentrations and for longer durations than blood, though exact dosage and ingestion timing are difficult to determine.

Hair (Toxicological Specimen)

A post-mortem or antemortem sample cut close to the scalp from the back of the head that grows approximately $1\,\text{cm}$ per month, useful for documenting long-term drug history and distinguishing between internal ingestion and external contamination.

Nails (Toxicological Specimen)

Keratin-rich structures collected as clippings or intact whole units that contain keratin $4\times$ thicker than hair, used to assess chronic drug exposure by trapping metabolites as the nail grows in thickness and length.

Saliva (Toxicological Specimen)

A non-invasive oral fluid sample suitable for detecting relatively recent drug consumption, though drug concentrations vary compared to blood and can be affected by food intake or drug-altered salivary flow.

Liver (Toxicological Specimen)

The primary solid organ tissue collected deep within the right lobe during post-mortem examination, which processes drugs and often retains high concentrations of parent compounds and metabolites long after they clear the bloodstream.

Vitreous Humour

An anatomically isolated, stable, clear fluid in the eyeball that can be collected up to $4\text{ days}$ after death, useful for post-mortem blood alcohol comparison and identifying hydrophilic drugs such as cocaine and heroin.

Lungs (Toxicological Specimen)

A whole left or right organ specimen primarily evaluated on a qualitative (yes/no) basis when volatile substance abuse, toxic gas inhalation, or drowning is suspected.

Stomach Contents

The entire gastric contents collected during autopsy—with intact pills or tablets isolated separately—to locate the primary ingestion source of an acute drug or poison exposure.

Forensic Chemistry

The identification and chemical analysis of non-biological unknown physical evidence recovered from crime scenes (such as powders, drug paraphernalia, cigarettes, and plant materials) to identify active drugs and cutting additives.

Presumptive Drug Tests

Initial on-the-spot or bench screening methods—including colorimetric assays, crystal morphology observation, and UV spectroscopy—used to quickly characterize a suspect substance and direct subsequent confirmatory protocols.

Marquis Test

A presumptive chemical spot test using $2\%$ formaldehyde in a sulfuric acid solution that turns purple for opiates (heroin, morphine), orange for amphetamines and methamphetamines, blue/black for ecstasy (MDMA), and bubbles without color change for cocaine.

Dille-Koppanyi Test

A two-step colorimetric screening test for barbiturates involving the sequential addition of $1\%$ cobalt acetate followed by $5\%$ isopropylamine in methanol, yielding a violet-blue reaction.

Duquenois-Levine Test

A presumptive reagent test for marijuana that combines Solution A ($2\%$ vanillin and $1\%$ acetaldehyde in ethyl alcohol), Solution B (concentrated hydrochloric acid), and Solution C (chloroform), confirmed positive when the chloroform layer turns purple.

Van Urk Test

A colorimetric test for detecting LSD (lysergic acid diethylamide) using $1\%$ p-dimethylaminobenzaldehyde in $10\%$ concentrated hydrochloric acid and ethyl alcohol, developing a dark blue-purple hue.

Scott Test

A three-stage presumptive colorimetric assay for cocaine using cobalt thiocyanate in water:glycerine ($1:1$), hydrochloric acid, and chloroform, yielding a sequential blue, then pink, then blue chloroform layer result.

Microcrystalline Test

A presumptive identification technique where a specific chemical reagent is added to an isolated substance on a microscope slide to observe the growth of distinct, substance-specific crystalline structures.

Confirmatory Drug Tests

Definitive multi-step analytical protocols combining physical separation techniques (such as GC, LC, or electrophoresis) with spectral identification to verify an unknown substance against certified reference standards.

Mass Spectrometry

A confirmatory instrumental method where vaporized molecules are bombarded with high-energy electron beams, shattering them into characteristic fragment ion spectra compared against reference libraries.

Infrared Spectroscopy

A confirmatory analytical technique examining the absorption of infrared energy by chemical bonds, measuring atomic vibrational modes to identify organic functional groups.

Drug Scheduling Criteria (US)

The federal regulatory classification criteria that categorize controlled substances based on four specific metrics: potential for abuse, safety, addictive potential, and legitimacy of accepted medical use.

Schedule I Drugs

Substances classified under US drug law as having high abuse potential, no currently accepted medical usage, and lack of accepted safety (e.g., heroin, LSD, peyote, MDMA).

Schedule II Drugs

Controlled substances with high potential for abuse and severe dependence liabilities, but accepted for severely restricted medical applications (e.g., cocaine, methamphetamine, methodone, oxycodone, ritalin).

Schedule III Drugs

Therapeutic substances with accepted medical utility, moderate abuse potential, and moderate-to-low physical or high psychological dependence liability (e.g., barbiturates, anabolic steroids, ketamine, testosterone).

Schedule IV Drugs

Pharmaceutical medications widely employed in clinical practice that carry low abuse liability and limited risks of physical or psychological dependence (e.g., Xanax, Valium, and other tranquilizers).

Schedule V Drugs

Prescription or over-the-counter preparations with very low potential for abuse containing limited quantities of narcotic ingredients (e.g., Robitussin, paracetamol, lomotil).