Transcript Ch. 10- Toxicology Notes

Forensic Toxicology
Forensic Toxicology
• Definition:
• The science of detecting and
identifying the presence of drugs
and poisons in body fluids, tissues,
and organs.
Controlled Substances Act
• Federal Law established 5
schedules of classification of
controlled substances based on
– Drug’s potential for abuse
– Potential to physical and
psychological dependence
– Medical Value
• Note: Federal law also controls
materials that are used in making
drugs and those that are manufactured
to resemble drugs
Role of the Toxicologist
• Must identify one of thousands of
drugs and poisons
• Must find nanogram to microgram
quantities dissipated throughout the
entire body
• Not always looking for exact
chemicals, but metabolites of
desired chemicals (ex. heroin 
morphine within seconds)
Toxicology Procedures
• 10mL of blood in airtight container
– Add anticoagulant
– Add preservative
• 2 consecutive urine samples
– Some drugs take a while to show up in
urine (1-3 days)
• Vitreous humor
• Hair samples
Toxicology Procedures
• Screening– quick test to narrow down possibilities
– color tests, TLC, GC, immunoassay
• Confirmation– determines exact identity
– GC/Mass Spec
Note: TLC—thin layer
chromatography
Why?
• Think of all the people that you have
“heard” do drugs.
• US drug manufacturers produce enough
barbiturates and tranquilizers each year
to give every person in the US 40 pills
• (that’s about 12 billion pills)
• 18,000 out of 44,000 annual traffic deaths
are alcohol related and send over 2
million people to the hospital
Toxicology of Alcohol
• Alcohol is absorbed through the
stomach and intestine
• Once absorbed, alcohol is:
– Oxidized- in liver by alcohol
dehydrogenase—turned into acidic
acid
– Excreted- by breath, perspiration, and
kidneys—turned into carbon dioxide
and water
Factors that Affect Alcohol
Absorption
• Time of
consumption
• Type of alcoholic
beverage
• Presence of food
in stomach
Toxicology of Alcohol
• Alcohol intoxication depends on
– Amount of alcohol consumed
– Time of consumption
– Body weight
– Rate of alcohol absorption
Fate of Alcohol
• Alcohol is absorbed into the
bloodstream
• Distributed through-out the body’s
water
• And finally eliminated by oxidation
and excretion
Fate of Alcohol Con’t
Note:
A. Oxidation is the combination of
oxygen and alcohol to produce
new products by the liver
B. Elimination is removing alcohol
from the body in an unchanged
state; normally excreted in breath
and urine
Alcohol in the Circulatory
System
• Measuring the quantity of alcohol in
the blood system determines the
degree to which someone is drunk
• Two methods of making this
measurement
– Measurement of alcohol content in
blood
– Measurement of alcohol in breath
Circulation and Alcohol
Circulation Definitions
• Artery—a blood vessel that carries blood
away from the heart
• Vein—a blood vessel that transports
blood toward the heart
• Capillary—a tiny blood vessel—walls
exchange materials between blood and
tissues
• Alveoli—small sacs in lungs—exchange
vapors between breath and blood
Circulation Con’t
• Note: If alcohol is present, it will be
passed from the blood into the alveoli
where it will be passed on to the mouth
and nose during the act of breathing.
• Evidence has shown that the ratio of
alcohol to alveoli air is approx. 2100 to
1—This is a basis for relating breath to
blood-alcohol concentration.
Analysis of BAC
• Breath Tests
• Field Sobriety Tests
• Blood Tests
Breath Tests
• A breath test reflects the alcohol
concentration in the pulmonary
artery.
• One instrument used for breath tests
is called The Breathalyzer.
• The Breathalyzer is a device for
collecting and measuring the alcohol
content of alveolar breath.
The Breathalyzer
The Breathalyzer Con’t
• The Breathalyzer traps 1/40 of 2100
milliliters of alveolar breath.
• Since the amount of alcohol in 2100
milliliters of breath approximates the
amount of alcohol in 1 milliliter of
blood—the Breathalyzer in
essence measures the alcohol
concentration present in 1/40 of a
milliliter of blood.
Breathalyzer Con’t
• Once the alveolar breath is trapped it is
allowed to undergo a chemical reaction:
•
2K2Cr2O7 + 3C2H5OH + 8H2SO4  2Cr2(SO4)3 + 2K2SO4 + 3CH3COOH + 11H2O
Potassium
dichromate
Ethyl
alcohol
Sulfuric
acid
Chromium
sulfate
Potassium
sulfate
Acetic
acid
Dihydrogen
oxide
• The Breathalyzer indirectly determines the quantity of alcohol
consumed by measuring the absorption of light by potassium
chromate before and after its reaction with alcohol, using the
principle of spectrophotometry
Other Breath Tests
• Infrared breath-testing instrument
• Fuel cell
• Note: These instruments are used
more recently because they don’t
depend upon chemical reagents and
are entirely automated.
Infrared-Breath Test
• Uses the principle that infrared light is
absorbed when shined on alcohol
• Essentially, the infrared light passes
through a chamber where it will interact
with the alcohol and cause the light
density to decrease.
• The decrease in light intensity is
proportional to the concentration of
alcohol present in the captured breath
Fuel Cell—Breath Test
• A fuel cell converts a fuel and an
oxidant into an electrical current.
• In this test, the breath alcohol is the
fuel and atmospheric oxygen acts as
the oxidant.
• Alcohol is converted, generating a
current that is proportional to the
quantity of alcohol present in the
breath.
Infrared and Fuel Cell
Breath Tests
• Infrared Breath Test
uses infrared
wavelengths to test for
alcohol or other
interferences in the
breath
• Fuel Cell Test
converts fuel
(alcohol) and
oxygen into a
measurable electric
current
Field Sobriety Testing
•
Two reasons for the field sobriety
test:
1. Used as a preliminary test to
ascertain the degree of the suspect’s
physical impairment
2. To see whether or not an evidential
test is justified.
Field Sobriety Testing
Methods
• Field sobriety testing consists of a
series of psychophysical tests and a
preliminary breath test (typically
done with a handheld fuel cell tester)
• These tests are preliminary and
nonevidential in nature—they only
serve to establish probable cause
requiring a more thorough breath or
blood test.
Field Sobriety Tests
• Horizontal Gaze Nystagmus
– Involuntary eye jerk as eye moves horizontally
• Walk and Turn (divided attention tasks)
• One-Leg Stand
Parts of the brain affected
by Alcohol
• Alcohol 1st
affects the
forebrain
and moves
backward
• Last
affected is
medulla
oblongata
Alcohol
and the Law
• 1939-1964:
intoxicated =
0.15% BAC
• 1965: intoxicated =
0.10% BAC
• 2003: intoxicated =
0.08% BAC
At least we don’t live in
France, Germany,
Ireland, or Japan
(0.05%) or especially
Sweden (0.02%)!
Alcohol and the Law
• Try the drink wheel:
http://www.intox.com/wheel/drinkwheel.asp