Forensic Toxicology

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Forensic Toxicology
Ch 5 pages 61-77

• All substances are poisons. There is none which
  is not. The right dose differentiates a poison
  and a remedy
• -Paracelsus (1495-1541)
• Swiss physician and chemist

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I. Introduction

• Forensic toxicology is the study of poisons as
  they pertain to legal matters.

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II. Applications of Forensic Toxicology

• 3 main areas
• Postmortem Drug testing
• Workplace drug testing
• Investigation of contraband materials

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A. Postmortem Drug Testing

• Postmortem Drug testing consists of a death
  investigation with a goal of establishing whether
  drugs were the cause or a contributing factor.
• Accidental or deliberate overdose

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B. Workplace Drug Testing

• Workplace Drug Testing consist of the evaluation
  of biofluids, (urine, blood) from employees or
  applicants, for drug content.

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C. Investigation of Contraband materials

• Evaluation of Contraband materials is used to
  identify prohibited drugs.
• Labs prove that seized material is illegal or not.

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IV. Testing Process Specimen Collection

• 1. Blood
• Is the most important specimen
• 2 sample are taken from heart and then
  peripheral site
• Concentration of toxins in blood is more accurate
  than any other fluid

• 2. Urine
• Is beneficial b/c large amounts can be collected
• Drug concentration level is usually low

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• 4. Hair
• Not common in Forensic toxicology investigations
  because drugs in the hair are extremely low
• Can show passive exposure
• Can show a long term exposure to drugs

• 3. Gastric Contents
• Is beneficial in the case of a deceased who has
  ingested large amounts of lethal agents
• Usually in the case of suicide

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• 5. Vitreous Humor
• Fluids from the eye
• Is resistant to breakdown, and takes a long time
  to decay
• Can also be used to estimate time of death
• 6. Bile and Liver
• May contain significant quantities of most drugs
  because the liver is used in metabolism of drugs

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Drugs of Abuse

• Drugs cited in the National Laboratory
  Certification Program
• Amphetamines
• Opiates
• Phencyclidine
• Cocaine
• Cannabinoids

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Amphetamines

• Amphetamines and methamphetamines
• Stimulants that create an excitable condition
  characterized by an elevation in heart rate,
  blood pressure, and respiratory rate.
• Cause intense euphoria
• Include ephedrine, phenylpropanolamine,
  phenylephrine,

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Opiates

• Opiates
• Constitute a large class of drugs distinguished
  by their ability to cause profound euphoria.
• High potency pain relievers
• Classified as depressants, reduced muscle
  activity, depressed respiration, heartbeat,
  inclination to sleep
• Grow in large amounts in Asia
• Include morphine, codeine, heroin, OxyCotin,
  hydrocodone, oxycdone,

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Phencyclidine

• Phencyclidine
• Aka. PCP, or peace pill
• Originally intended for use as a surgical
  anesthetic
• Users show euphoria, feelings of detachment,
  strength, power, severe perceptual distortions,
  violent behavior, psychosis, paranoia, and
  hallucinations

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Cocaine

• Cocaine
• Is a stimulant that resembles amphetamine in its
  abusive potential
• Is a natural product that include free base,
  crack

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Cannabinoids

• Cannabinoids
• The related psychoactive compounds that come from
  the plant Cannabis Sativa.
• Aka. Marijuana
• Tetrahydrocannabibol (THC) is the active agent
• Drug state includes mood swings, euphoria,
  perceptive alterations, memory impairment, low
  motivation

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Analytical Methods in Forensic Toxicology

• 1. The approach to testing for substances has 2
  parts
• screening
• confirmation

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Screening Tests

• Immunoassays
• are tests in which antibodies are used.
• -they enable the regents to react only with a
  substance that recognizes the antibody.

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Screening Tests

• 2. Thin Layer Chromatography
• (TLC) the specimen is extracted into an organic
  solvent and spotted onto a glass plate coated
  with silica
• the plate is placed into a tank that separates
  whatever chemicals were originally present in the
  specimen.
• Toxins are identified by the distance they
  migrate up the plate

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Screening Tests

• 3. UV Visible Spectrophotometry
• most drugs absorb light
• each drug produces a characteristic spectrum that
  allows the drug to be identified because it has
  peak absorbance at a certain wavelength

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Confirmation analysis

• Gas Chromatography
• is a method in which substances are separated
  from other components of a mixture on a column
• Gas Chromatography Mass Spectrometry
• is a combined method in which substances are
  separated from other components of a mixture on
  a column and a mass spectrum is also obtained
• Bombarded with electrons

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Interpreting Drug Findings

• The goal of a forensic toxicologist in a
  postmortem investigation is to collaborate with
  the forensic pathologist in determining the cause
  and manner of death

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Non medicinal Agents

• Many deaths are due to chemicals that are not
  medicinal and/or are encountered in the
  environment.
• Alcohol
• Cyanide
• Carbon Monoxide
• Hydrocarbons
• Heavy Metals

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Alcohols

• Ethanol is beverage alcohol
• Enter the membranes of the nerve cells and
  disrupt their normal architecture
• Contributes to numerous disorders as a result of
  a chronic abuser (Liver and brain)
• Is usually measured by gas chromatography

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Cyanide

• Highly toxic substance found in many forms
• gas hydrogen cyanide
• solid sodium cyanide
• death occurs quickly
• antidotes can save those exposed to only small
  amounts

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Carbon monoxide

• CO, prevents the transport of oxygen
• Causes more deaths that any other toxic substance
• Present in fires, car exhaust

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Hydrocarbons

• Are commonly found in nature..
• Death is due to high exposure, or accident
  following erratic behavior brought on by the
  effects of hydrocarbons on the brain
• Hydrocarbons can be gases (methane and propane),
  liquids (hexane and benzene), waxes or low
  melting solids (paraffin wax and naphthalene) or
  polymers (polyethylene, polypropylene and
  polystyrene).

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Heavy Metals

• individual metals and metal compounds that
  negatively affect people's health.
• in larger amounts, they become toxic. They may
  build up in biological systems and become a
  significant health hazard.
• Arsenic
• Beryllium
• Lead
• Mercury
• Cadmium