Download Forensic Toxicology

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
I. Introduction
 Forensic toxicology
is the study of
poisons as it pertains
to legal matters.
II. Applications of
Forensic Toxicology
 3 main areas:
 Postmortem Drug
testing
 Workplace drug
testing
 Investigation of
contraband materials
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
B. Workplace Drug Testing
 Workplace Drug
Testing consist of
the evaluation of
biofluids, (urine,
blood) from
employees or
applicants for drug
content.
C. Investigation of
Contraband materials
 Evaluation of
Contraband
materials is used to
identify prohibited
drugs.
 Labs prove that
seized material is
illegal
IV. Testing Process
Specimen Collection
1. Blood:
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Is the most
important specimen
2 sample are taken;
from heart and then
peripheral site
Concentration of
toxins is more
accurate than any
other fluid
2. Urine:
 Is beneficial… b/c
large amounts can be
collected
 Drug concentration
level is usually low
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
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
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
Drugs of Abuse
 Drugs cited in the
National Laboratory
Certification Program
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Amphetamines
Opiates
Phencyclidine
Cocaine
Cannabinoids
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,
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,
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
Cocaine
 Cocaine
 Is a stimulant that
resembles
amphetamine in its
abusive potential
 Is a natural product
that include “free
base”, “crack”
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
Medical Agents involved in
Death
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Sedative Hypnotics
Cardioactive Agents
Antipsychotic agents
Antiepileptic agents
Antidepressants
 Death may occur
because of
 errors in dosage,
mixing, and/or taking
the wrong
medications,
 Organ damage that
prevents metabolism,
 A build up of levels in
the blood that
become toxic.
Analytical Methods in
Forensic Toxicology
1. The approach to testing for substances
has 2 parts:
 screening
 confirmation
Screening Tests
Immunoassays
 – are tests in which
antibodies are used.
 -they enable the
regents to react only
with a substance that
recognizes the
antibody.
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
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
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
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
Non medicinal Agents
 Many deaths are due to chemicals that
are not medicinal and/or are encountered
in the environment.
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Alcohol
Cyanide
Carbon Monoxide
Hydrocarbons
Heavy Metals
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
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
Carbon monoxide
 CO, prevents the transport of oxygen
 Causes more deaths that any other toxic
substance
 Present in fires, car exhaust
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).
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