Transcript Forensic Toxicology

Forensic Toxicology
Section 1
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2.
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Objectives
Explain how alcohol is absorbed into the
bloodstream, transported throughout the body,
and finally eliminated by oxidation and
excretion.
Name the important parts of the human
circulatory system.
Describe the process by which alcohol is
excreted in the breath via the alveoli.
Describe the design of the Breathalyzer.
Explain the significance of a chemical equation.
Explain the concept of infrared and fuel-cell
breath-testing devices.
Demonstrate some common field sobriety tests.
List common laboratory procedures for
measuring alcohol’s concentration in the blood.
Created by C. Ippolito Feb 2008
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Role of Forensic Toxicology
Uncontrolled use of drugs has
increased world wide importance of
the field
Toxicologist
detect and identify drugs and poisons in
body fluids, tissues, and organs
– test lead exposure in children
– urine analysis for drug treatment programs
– urine analysis of prospective employees
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Toxicology of Alcohol
Ethyl alcohol – most abused drug
responsible for 40% of traffic deaths
17,500 fatalities per year
hospitalizations from injuries
2 million per year
Metabolism
chemical reactions in an organism
Alcohol Metabolism
absorption – how it gets into systems
distribution – how it moves through body
elimination – how it is removed from body
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Alcohol Metabolism
Absorption
slowly enters
bloodstream
in stomach
in small intestines
Factors affecting
adsorption:
time taken to consume
amount consumed
alcohol content of
beverage
quantity and type of food
in stomach
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Alcohol Metabolism (con’t)
Distribution
equally distributed into watery parts of (2/3)
body
Elimination (0.015% per weight/volume
per hour)
Oxidation in liver (95-98%)
alcohol dehydrogenase
– alcohol  acetaldehyde  acetic acid
– acetic acid  carbon dioxide and water
Excretion
lungs (breath)
kidneys (urine)
sweat glands (perspiration)
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Blood Alcohol Concentration
How much alcohol impairs brain function
[blood alcohol] directly proportional [brain
alcohol]
maximum [blood alcohol] may not be
reached for 2-3 hours after consumption
usually 20-30 minutes after final drink
absorption is completed
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Alcohol Ingestion and Distribution
Closed Circulatory
System
heart (pump)
arteries - carry blood
away from heart
capillaries - exchange
blood with tissue
veins - returns blood
from tissues to heart
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Alcohol Aeration
Lungs
alveoli
oxygen and carbon
dioxide exchange
Henry’s Law
volatile in liquid reached
equilibrium with air at a
fixed ratio that is constant
at a given temperature
at 34°C ratio is 2100 to 1
so that 1 mL of blood has
the same [alcohol] as
2100 mL of breath
basis of breathalyzer tests
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Alcohol Recirculation and
Adsorption
arterial blood sends alcohol to tissues
[alcohol] in arteries > [alcohol] in veins
up to 41% higher 30 mins after last drink
does not equalize until adsorption stage
is completed
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Breath Testing for Alcohol
Measures [alcohol] in pulmonary
artery by measuring [alcohol] in
alveolar breath
during absorptive phase will be higher
than [alcohol] in veins
Breathalyzer
developed 1954 by R. Borkenstein of
Indiana State Police
Infrared Light Absorption Devices
Fuel Cell Detectors
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Breathalyzer Test
52.5 mL collected
passed through
potassium dichromate
reacts with alcohol
forming acetic acid
silver nitrate acts as
catalyst
2 to 3 ratio
for every 2 units of
potassium dichromate
used 3 units of alcohol
was present
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Infrared Light Adsorption Devices
microprocessor
controlled
self calibrating
breath collected
IR light passed through
chamber
filter selects IR
wavelength alcohol
absorbed
detector measures
alcohol present
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Fuel Cell Device
microprocessor controlled
self calibrating
platinum electrodes
separated by porous acid or base
containing membrane
alcohol  acetic acid + free electrons
current formed is proportional to alcohol
in breathe
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Consideration in Breath Testing
need alveolar breathe (1.1 – 1.6 L)
slope detector insures this
avoid “mouth alcohol”
regurgitation, mouth wash, etc
observe 15 to 20 minutes before test
take duplicate samples
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Field Sobriety Testing
psychophysical tests
degree of impairment
whether evidential test justified
Alco-Sensor FST
Horizontal-gaze Nystagmus
involuntary jerk moving eye
Walk and Turn
heel to toe walk for nine steps
turn and heel to toe walk back
One-Leg Stand
stand on one foot and count out loud
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Forensic Toxicology
Section 2
1.
2.
3.
4.
5.
6.
7.
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Objectives
Describe the precautions to be taken to properly
preserve blood for analysis for its alcohol content.
What is the presumptive impairment level for blood
alcohol in your state?
Explain the significance of the implied consent law
and the Schmerber v. California case to traffic
enforcement.
Define acid and base.
Develop an appreciation for the role of the toxicologist
in the criminal justice system.
Describe some of the techniques that forensic
toxicologists use for isolating and identifying drugs
and poisons.
Discuss the significance of finding a drug in human
tissues and organs.
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Analysis of Blood for Alcohol
gas chromatography
alcohol has definite
peak
peak size can be
compared to knowns
alcohol
dehydrogenase NAD
reaction
converts NAD to
NADH
measurable by
spectrophotometer
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Collection and Preservation of
Blood
blood drawn by qualified person
use nonalcoholic disinfectant
Zepiran or Betadine
sealed in airtight container
anticoagulant (EDTA potassium oxalate)
preservative (sodium fluoride)
refrigerate
postmortem
bacteria produce ethanol
prefer vitreous humor or urine to limit this effect
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Alcohol and the Law
AMA and NSC
establish uniform / reasonable
blood alcohol levels
Blood-Alcohol Laws
AMA NSC
0.15% w/v under influence
1992 DOT recommends lower
0.08% w/v under influence
– 2003 states not lose fed funds
Commercial Drivers
0.04% w/v under influence
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Created by C. Ippolito Feb 2008
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Constitutional Issues
Fifth Amendment
protects from self-incrimination
NSTA implied-consent law
refusing test leads to loss of license
Schmerber vs. California
blood take w/o consent after accident led to
conviction
Supreme Court
– 5th Amendment prohibits testimonial self incrimination
– does not apply to furnishing physical evidence
– 4th Amendment (unreasonable search)
» emergency situation warranted taking
» taken in accepted manner without unreasonable
force
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Role of Toxicologist
w/o clue needs extensive “screening”
using small amounts
micrograms if not nanograms
body actively alters substances
i.e. heroin is immediately metabolized to
morphine which can combine with carbs
in body and not end up in urine samples
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Toxicological Techniques
Acid/Base
control pH affects drug removal
Acid – barbiturates and aspirin
Basic – phencyclidine, methadone, amphetamine, cocaine
Screening Tests
TLC, GC, Immunoassay (monoclonal antibodies)
Confirmation Tests
GC followed by MS
Hair Analysis
used for measuring long term abuse
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Other techniques
Reinsch Test
screens for heavy metals
treat body fluid with HCl
– copper strip in fluid darkens heavy metal present
– followed with more detailed inorganic analysis
CO poisoning
spectrophotometer
reagent followed by GC
find percent saturation
– 35-40 percent is fatal
– 8-10 percent seen in chain smokers
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