Forensic Toxicology & Drug Chemistry

A comprehensive flashcard deck covering key concepts in forensic toxicology and drug chemistry, including drug scheduling, testing methods, specimen types, and legislative context.

Who collects toxicology specimens during an autopsy?

The forensic pathologist or medical examiner.

What is the “chain of custody”?

The documented path of evidence from collection to courtroom ensuring no tampering occurred.

What happens if the chain of custody is broken?

The evidence may be ruled inadmissible in court.

What specimens are most useful in postmortem toxicology?

Blood, urine, liver, vitreous humour, bile, hair, gastric contents.

Why are multiple specimens tested?

To confirm consistency and eliminate false negatives/positives from decomposition or contamination.

Why might vitreous humour be used for alcohol testing?

It resists postmortem decomposition and shows BAC more reliably than blood.

Why are pre-hospital admission blood samples important?

They show true antemortem concentrations before metabolism or treatment interference.

What toxicology result is considered “screening only”?

A positive immunoassay result without GC-MS confirmation.

Recommended specimens for Suicide / motor vehicle / industrial accident

Blood, urine, vitreous humour, liver

Recommended specimens for Homicide / suspicious death

Blood, urine, vitreous humour, gastric contents, bile, liver, hair

Recommended specimens for Drug-related death

Blood, urine, vitreous humour, gastric contents, bile, liver, hair

Recommended specimens for Volatile substance abuse

Blood, urine, vitreous humour, lung fluid or tied-off lung, liver

Recommended specimens for Heavy metal poisoning

Blood, urine, vitreous humour, liver, hair, kidney

Why is hair useful for toxicology?

It provides a long-term exposure record (weeks to months).

Why are stomach contents tested?

To identify undissolved pills or poisons in acute overdose cases.

Why is the liver so valuable in toxicology?

It’s where most drug metabolism occurs, and drugs concentrate there.

Why is urine often tested even though it doesn’t show intoxication?

It shows recent use via drug metabolites.

What’s the purpose of presumptive testing?

To indicate a drug may be present (field or lab screening).

What’s the purpose of confirmatory testing?

To definitively identify the drug using advanced instrumentation.

Examples of presumptive tests?

Colorimetric, microcrystalline, UV spectroscopy, microscopic analysis.

Examples of confirmatory tests?

GC-MS, LC-MS, IR spectroscopy, capillary electrophoresis.

What is GC-MS used for?

Separating and identifying components by mass spectral fingerprint.

What does LC-MS stand for?

Liquid Chromatography–Mass Spectrometry. Used for heat-sensitive drugs.

What does IR spectroscopy detect?

Bond vibrations to determine functional groups and compound identity.

What does capillary electrophoresis use to separate compounds?

An electric field.

What’s the difference between qualitative and quantitative tests?

Qualitative = “what’s there”; Quantitative = “how much is there.”

Why is immunoassay used as a first screen?

It’s fast, detects broad drug classes via antibodies, and cheap.

What’s the most reliable confirmatory test used in forensic toxicology?

GC-MS (Gas Chromatography–Mass Spectrometry).

Characteristics and examples of Schedule I drugs?

No accepted medical use, high abuse potential – Heroin, LSD, MDMA, Marijuana (federally).

Characteristics and examples of Schedule II drugs?

Restricted medical use, high abuse potential – Cocaine, Methamphetamine, Oxycodone, Fentanyl.

Characteristics and examples of Schedule III drugs?

Moderate abuse potential – Ketamine, Anabolic steroids, Barbiturates.

Characteristics and examples of Schedule IV drugs?

Low abuse potential – Xanax®, Valium®, Ambien®.

Characteristics and examples of Schedule V drugs?

Lowest abuse potential, limited narcotics – Robitussin® AC, Tylenol® with Codeine.

Which act established drug schedules in the U.S.?

The Controlled Substances Act.

Why are Schedule I drugs federally illegal?

They’re considered to have no accepted medical use.

Who enforces drug scheduling?

The Drug Enforcement Administration (DEA).

What determines drug scheduling?

Medical value, abuse potential, and physical/psychological dependence risk.

Common effects and examples of Stimulants?

Increased alertness, energy, euphoria – Cocaine, Amphetamines, Methamphetamine.

Common effects and examples of Depressants?

Relaxation, slowed CNS activity – Alcohol, Benzodiazepines, Barbiturates.

Common effects and examples of Narcotics (Opiates)?

Pain relief, euphoria, drowsiness – Heroin, Morphine, Codeine, Oxycodone.

Common effects and examples of Hallucinogens?

Altered perception, hallucinations – LSD, PCP, Psilocybin.

Common effects and examples of Cannabinoids?

Euphoria, relaxation, impaired coordination – THC (Marijuana).

Common effects and examples of Synthetic Drugs?

Unpredictable, psychotic effects – Synthetic cannabinoids (“Spice”), Bath Salts.

Common effects and examples of Inhalants?

Euphoria, disorientation, slurred speech – Butane, Nitrous Oxide.

Common effects and examples of Steroids?

Aggression, mood swings, muscle growth – Testosterone, HGH.

What’s the first step once evidence reaches the lab?

Documentation, labeling, and storage under chain of custody.

What test determines how much of a substance is present?

Quantitative test.

What test determines what substance is present?

Qualitative test.

What does the “Scientific Working Group for the Analysis of Seized Drugs” (SWGDRUG) do?

Publishes guidelines for drug analysis in forensic labs.

What’s the role of a forensic chemist in court?

Provide expert testimony on testing methods and drug identity.

What is a “true positive” in testing?

When the test correctly detects a drug that is present.

What’s a “false negative”?

When the test fails to detect a drug that is actually present.

What’s the main purpose of toxicology in a death investigation?

To determine whether toxic substances contributed to or caused death.

Why can toxicology show positive results in non-drug deaths?

Some drugs indicate medical treatment or incidental use.

What’s post-mortem redistribution?

The movement of drugs between tissues after death, affecting concentration levels.

Why might alcohol and drugs appear in many traffic deaths?

Impaired driving and reaction times increase fatal crash likelihood.

Why can a positive toxicology result not always mean cause of death?

The concentration may not be lethal or relevant to cause of death.

Who certifies forensic toxicologists in the U.S.?

The American Board of Forensic Toxicology (ABFT).

What organization regulates forensic lab accreditation?

ANAB / ASCLD-LAB.

What’s the goal of “SWGTOX”?

To set national standards for forensic toxicology testing and reporting.

What is EuroTox?

The European Register of Toxicologists certification program.

What’s the role of a forensic chemist vs a toxicologist?

Chemist identifies drugs in seized materials; toxicologist identifies drugs in biological samples.

Define pharmacodynamics.

What a drug does to the body (mechanism/receptor effects); contrasts with pharmacokinetics (what the body does to the drug).

Define pharmacokinetics (ADME).

Absorption, Distribution, Metabolism, Excretion; determines onset, intensity, and duration.

Potency vs efficacy?

Potency = dose needed for effect ( EC{50} ), efficacy = maximal effect ( E{max} ); high potency ≠ high efficacy.

Agonist, partial agonist, antagonist?

Agonist activates fully, partial agonist activates partially, antagonist blocks receptor; partials can blunt full agonists.

Inverse agonist vs antagonist?

Inverse agonist reduces basal activity; antagonist only blocks agonist without changing baseline.

Competitive vs noncompetitive antagonism?

Competitive shifts dose–response right (surmountable); noncompetitive lowers E_{max} (insurmountable).

Therapeutic index (TI)?

TI = TD{50}/ED{50} (or LD{50}/ED{50} ); wider TI = safer.

First-pass metabolism—what is it?

Hepatic/intestinal metabolism before systemic circulation; reduces oral bioavailability.

Bioavailability (F) definition.

Fraction of dose reaching systemic circulation unchanged; IV = 1, oral < 1.

Volume of distribution (Vd) meaning.

Theoretical volume that accounts for drug distribution; high Vd suggests tissue binding.

Clearance (Cl) concept.

Volume of plasma cleared of drug per unit time; determines maintenance dose rate.

Half-life (t½) rules of thumb.

~5 half-lives to steady state or elimination; depends on Vd and Cl.

Zero-order vs first-order elimination?

Zero-order = constant amount/time (capacity-limited), first-order = constant fraction/time.

CYP450 most common hepatic phase I?

Oxidation via CYP3A4, 2D6, 2C9, etc.; polymorphisms matter.

Phase II conjugation examples.

Glucuronidation, sulfation, acetylation; usually inactivating and increases polarity.

Tolerance vs dependence vs addiction?

Tolerance = diminished effect; dependence = withdrawal on cessation; addiction = compulsive use despite harm.

Upregulation vs downregulation of receptors?

Chronic antagonism → upregulation; chronic agonism → downregulation; informs withdrawal/tapering.

Blood–brain barrier favors what?

Lipophilic, small, non-ionized drugs; ion trapping occurs with pH differences.

Ionized vs non-ionized—who crosses membranes?

Non-ionized crosses; Henderson–Hasselbalch explains pH-dependent trapping.

Pharmacodynamic drug–drug interaction example.

Benzos + alcohol → synergistic CNS depression; same direction on outcome.

Pharmacokinetic drug–drug interaction example.

CYP3A4 inhibitors raise fentanyl levels; altered concentration drives effect.

Chain of custody—why critical?

Documents evidence handling end-to-end; breaks can exclude evidence in court.

Postmortem redistribution (PMR)—what is it?

Concentration shifts after death (central > peripheral); prefer femoral blood.

Preferred blood site in autopsy toxicology?

Peripheral (femoral/subclavian) to minimize PMR effects.

Urine utility in tox?

Great for detection window (metabolites), poor for impairment at time of event.

Vitreous humour—why useful?

Stable matrix; good for ethanol (often ~20% higher than blood) and electrolytes.

Liver in tox interpretation?

Metabolic “sink”; can detect drugs when blood negative but interpretation is complex.

Hair testing window?

Weeks–months; shows chronic exposure but susceptible to external contamination.

Nails vs hair?

Longer window than hair; interpretation less well-characterized.

Stomach contents helpful when?

Acute ingestion/overdose—can see undissolved tablets and estimate unabsorbed load.

Immunoassay screen vs confirmatory test?

Immunoassay = presumptive (sensitive, cross-reactivity), GC-MS/LC-MS = confirmatory (specific).

Examples of presumptive lab tests.

Colorimetric kits, microscopic, microcrystalline, UV; indicate class not identity.

Confirmatory instruments of choice.

GC-MS, LC-MS/MS, FTIR; provide molecular identity and often quantitation.

SWGTOX/ABFT relevance.

Standards (SWGTOX) and certification (ABFT) assure validated methods and reliable interpretation.

Routine postmortem tox panel commonly includes?

Alcohols, benzodiazepines/Z-drugs, antidepressants, antihistamines, antipsychotics, opioids, cocaine, THC, stimulants.

“Special request” analytes often not in routine screen?

Barbiturates, digoxin, anticonvulsants (some), LSD, GHB, metals, pesticides, synthetic cannabinoids/cathinones.

DEA Schedule I hallmark.

No accepted medical use, high abuse (e.g., heroin, LSD, MDMA at federal level).

Schedule II examples.

Cocaine (medical), methamphetamine, oxycodone; high abuse, medical use.