Download Forenisc Toxicology

Chapter 6
FORENSIC TOXICOLOGY
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-1
Introduction
Toxicologists:
• detect and identify drugs and poisons in body
fluids, tissues, and organs
• identify a drug overdose or monitor the intake of
drugs
• work in crime laboratories, medical examiners’
offices, hospital laboratories and health facilities
• measure the amount of alcohol or other abused
drugs in the body for violations of criminal law
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-2
Toxicology of Alcohol
• Alcohol, or ethyl alcohol,
is a colorless liquid
normally diluted with
water and consumed by
many as a beverage.
• Like any depressant,
alcohol principally
effects the central
nervous system,
particularly the
functions of the brain.
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-3
Alcohol Levels
•
Appears in the blood a few
minutes after it has been
consumed.
•
Blood alcohol concentration
slowly increases as it is
absorbed from the stomach and
the small intestine.
•
Once its complete, absorbed
blood alcohol level reaches
maximum.
•
The post-absorption period
begins after maximum BAC is
reached.
•
Alcohol concentration slowly
decreases until level returns to
a zero.
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-4
Absorption Rates
Many factors
can effect
alcohol absorption rates:
• Time it takes to consume the
drink
• The alcohol content
• The volume of the drink
• Presence/absence of food in
the stomach and the type of
food
• Gender
• Body weight and height
• Genetics
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-5
Alcohol
• Is eliminated from the body through breakdown
(oxidation) and excretion.
• Alcoholic oxidation takes place in the liver.
• Alcohol is excreted in breath, urine, and sweat.
• Is measured as the quantity of alcohol present in
the blood (BAC) or the alcohol content in the
breath
• The amount of alcohol exhaled in the breath is
directly proportional to the alcohol concentration
in the blood
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-6
Alcohol & Circulatory System
• Humans have a closed
circulatory system
containing heart,
arteries, veins and
capillaries
• Alcohol is absorbed into
the blood stream from
the stomach and small
intestines.
• Some alcohol in the
blood is carried to the
liver where the process
of alcohol-breakdown
(oxidation) begins.
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-7
Alcohol & Circulatory System
• Other blood, carrying
alcohol, moves to the
heart and is pumped to
the lungs.
• In the lungs, carbon
dioxide and alcohol leave
the blood and oxygen
enters the blood in the
air sacs known as alveoli.
• There the carbon dioxide
and alcohol are exhaled
during normal
breathing.
http://www.intox.com/wheel/drinkwheel.asp
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-8
Breath Testers
• Breath testers are
designed to analyze a
specific volume of
breath.
• The captured breath is
exposed to infrared light.
• The infrared light source
allows the instrument to
measure the (BAC) in
the captured breath.
• Other breath testing
devices use fuel cells.
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-9
Portable Breath Testers
Many types of breath testers are designed
to analyze a set volume of alveolar breath.
The captured breath is exposed to infrared
light.
It’s the degree of the interaction of the
light with alcohol in the captured breath
sample that allows the instrument to
measure a blood alcohol concentration in
breath.
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-10
Field Testing
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
• Law enforcement
officers use field sobriety
tests to estimate physical
impairment by alcohol.
• The HGN (horizontal
gaze nystagmus), walk
and turn, and the one-leg
stand are reliable
psychophysical tests.
• A portable, handheld,
roadside breath tester
can be used to determine
a preliminary BAC.
• A confirmation blood
test is alwaysPRENTICE
performed
HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-11
Confirmation Blood Testing
• Gas chromatography is used
to determine specific alcohol
levels in blood.
• Blood must always be drawn
under controlled conditions
by qualified personnel.
• A nonalcoholic disinfectant
must be applied before the
suspect is stuck with a sterile
needle.
• The blood is collected in a
glass tube that contains
anticoagulant/preservative
and refrigerated.
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-12
Alcohol and Law
• The American Medical
Association and the
National Safety Council
convinced the separate
states to agree on an
under-the-influence
standard:
• 1939 to 1964 the BAC
was set at 0.15 %
• 1965 the BAC was
lowered to 0.10 %
• 1972 BAC was lowered
again to 0.08 %
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-13
Oklahoma University Police
BAC Calculator
• Web address:
http://www.ou.edu/o
upd/bac.htm
Theoretical BAC
based on
number/type
drink, weight and
hours drinking
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-14
Alcohol and Law
• In 2003, states adopted the 0.08 % “per se”
level.
• To prevent refusal to take a test for alcohol
consumption, the National Highway Traffic
Safety Administration recommended an
“implied consent” law:
• Adopted by all states by 1973, this law states
operating a motor vehicle on a public highway
automatically requires that the driver will
submit for a test for alcohol intoxication or be
subject to loss of the license.
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-15
Role of the Toxicologist
• A toxicologist must be able to identify many
drugs and poisons.
• The toxicologist examines body fluids and/or
organs for the presence of drugs and poisons.
• If supportive evidence, such as the victim’s
symptoms, a postmortem pathological exam,
or analysis of the victim’s personal effects, the
toxicologist is forced to use general screening
procedures with the hope of narrowing
thousands of possibilities to one.
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-16
Role of the Toxicologist
• The toxicologist is not dealing
with drugs at the
concentration levels found in
powders and pills, having
been digested and distributed
throughout the body.
• The body is an active
chemistry laboratory - few
substances enter and
completely leave the body in
the same chemical state.
• Toxicologists must be
prepared to assess the toxicity
of the drug or poison.
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-17
Toxicology Analysis
• The forensic toxicologist
must successfully detect,
isolate, and specifically
identify toxic drug
substances.
• Once the drug has been
extracted from appropriate
biological fluids, tissues and
organs, the toxicologist can
identify the drug.
• Most drugs are either acidic
or basic.
• Identifying abused drugs
requires two-steps:
1) screening
2) confirmation.
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-18
The Screening Step
• A screening test is used
to provide a general
classification of the
drug(s) contained in a
specimen
• Screening tests must be
verified with a
confirmation test
• The most common
screening tests are:
thin-layer chromatography
gas chromatography
immunoassay
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-19
The Confirmation Step
• Gas chromatography/mass spectrometry
the confirmation test of choice
• GC separates the sample into its
components
• MS represents a unique “fingerprint”
pattern that identifies the components.
• The toxicologist may be required to state
the effects of the drug(s) on the natural
performance or physical state of the
suspect/victim
FORENSIC SCIENCE
An Introduction
By Richard Saferstein
PRENTICE HALL
©2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
6-20