Forensic Toxicology Detailed Notes

Introduction to Forensic Toxicology

  • Definition of Toxicology: Study of non-food substances taken by living organisms.

    • Focuses on:

    • Amount taken

    • Physiological effects

    • Psychological effects

  • What is Forensic Toxicology?:

    • Involves the study of how drugs and poisons affect humans

    • Forensic toxicologist role begins when death occurs under suspicious circumstances

    • Collaboration with pathologists to determine cause and manner of death

    • Commonly involves cases related to ethyl alcohol and driving incidents.

Key Concepts in Forensic Toxicology

  • Pharmacology vs. Toxicology:

    • Pharmacology: Science studying drug interactions with living organisms.

    • Clinical Pharmacology: Effects of drugs on humans.

    • Toxicology: Focus on harmful drug effects, especially in suspicious circumstances.

    • Forensic Toxicologist: Scientist examining drugs in cases of death, impairment, or injury.

  • Drugs vs. Poisons:

    • Drug: Chemical designed to produce physiological/psychological effects.

    • Manufactured to elicit a specific response.

    • Poison: Substance that causes toxic effects.

    • Direct Effects: Intended by the maker, separate from unintended side effects.

Responsibilities of Forensic Toxicologists

  • Key Tasks:

    • Identify drugs and poisons in the body.

    • Determine quantities of substances present at death.

    • Identify metabolites created in the body.

    • Assess drug interactions’ significance.

    • Investigate drug use history, dependence, and tolerance.

Pharmacokinetics and Pharmacodynamics

  • Pharmacokinetics: Study of drug movement in the body (absorption, distribution, metabolism, elimination).

    • Absorption: Introduction through oral, intravenous, inhalation, etc.

    • Distribution: Drug dissemination via the bloodstream, varies by location in the body.

    • Metabolism: Chemical alteration of drugs into less active forms, primarily occurs in the liver.

    • Elimination: Drug excretion via urine; volatile substances can exit through respiration.

  • Pharmacodynamics: How drugs act on the body, focusing on receptor interactions.

    • Agonist: Drug that activates a receptor.

    • Antagonist: Drug that binds but does not activate.

Drug Dependence, Tolerance, and Synergism

  • Dependence: Physical or psychological reliance on a substance.

    • Physical dependence leads to withdrawal symptoms after cessation.

    • Psychological dependence does not result in withdrawal symptoms.

  • Tolerance: Body adapts to drug presence, needing increased doses for effect.

  • Synergism: Combined drugs producing effects greater than individual actions. Examples include alcohol with barbiturates.

Drug Identification Processes

  • Identification is often challenging due to limited information. Steps include:

    1. Sampling: Blood, urine, hair, body fluids, etc.

    2. Extraction: Cleaning up and concentrating samples.

    3. Screening: Preliminary tests indicating drug presence.

    4. Confirmation: Only mass spectrometry is accepted for confirming presence.

Cut-Off Levels and Thresholds

  • Cut-Off Levels: Below which drugs are considered undetected; varies between screening and confirmatory tests, measured in nanograms/milliliter for common substances (e.g., Marijuana is 50 for initial tests, 15 for confirmatory).

Workplace Drug Testing

  • Increased focus on employee drug testing requires strict adherence to chain of custody and standards.

    • Sampling issues arise, such as dilution or substitution.

    • Importance of mass spectrometry for confirmation to avoid false positives.

Forensic Toxicology of Ethyl Alcohol

  • Measurement of Alcohol: Blood Alcohol Content (BAC) and Breath Alcohol Content (BrAC) as measures of intoxication.

    • Forensic toxicologists estimate alcohol's effects and its role in death.

  • Acquisition of Alcohol: Primarily absorbed in the upper intestine; factors affecting absorption include drink type, consumption speed, and stomach contents.

  • Metabolism: Primarily occurs in liver (90% elimination), average rate is around 0.015%/hour.

    • Remaining alcohol is cleared through urine and breath.

  • Measurement of Alcohol Levels: Blood samples used for BAC analysis; gas chromatography for analysis. Breath testing is common in DUI scenarios using technologies like infrared spectroscopy.

Field Sobriety Testing and DUI Laws

  • Field Sobriety Testing: Performance tests help establish probable cause for further testing.

    • Includes tests like Horizontal Gaze Nystagmus, Walk and Turn, and Finger-to-Nose.

  • Legal Limits: Varies by state; 0.08% standard for impaired driving.

  • Lack of legal thresholds exists for drugged driving, focusing more on presence than concentration.