Transcript Forensic Toxicology

Forensic Toxicology
Forensic Toxicology
• Definition:
• The science of detecting and identifying
the presence of drugs and poisons in
body fluids, tissues, and organs for the
purpose of determining their influence on
human behavior.
•
a. needed to devise rapid and specific
procedures for measuring the degree of
alcohol intoxication..
The Drug Recognition
Expert
• 3-5 month training program for a police officer certifies an
officer as a DRE.
• The toxicologist can determine that a suspect has a certain
drug in their body, but they often cannot infer with
reasonable certainty that the suspect was impaired at a
specific time.
• The DRE evaluation process can suggest the presence of
the following seven broad categories of drugs as well as
determine the level of impairment:
•
depressants
•
stimulants
•
hallucinogens
•
phencyclidine
•
inhalants
•
narcotic analgesics
•
cannabis
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
Drug Schedules
• Schedule I:
• Drugs with high potential for abuse and
addiction, NO medical value
Ex: Heroin, LSD, Ecstasy, Marijuana
• Schedule II:
• Drugs with high potential for abuse and
addiction, have some medical value with
restrictions
Ex: PCP, Cocaine, Amphetamines, Most
Opiates, Some Barbiturates
Drug Schedules
• Schedule III:
• Drugs with less potential for abuse and
addiction, currently acceptable for
medical use
Ex: Some Barbiturates, Codeine, Steroids
• Schedule IV:
• Drugs with low potential for abuse and
addiction, currently acceptable for
medical use
Ex: Tranquilizers like Valium, Xanax,
Librium
Drug Schedules
• Schedule V:
• Drugs with low potential abuse,
medical use, lowest potential
dependency
• Ex: Some Opiates with Non-Narcotic
Ingredients
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)
• Toxicologist examines organs and/or
body fluids (usually blood and urine)
for the presence of drugs and
poisons.
•
a. clues are sometimes available
from the victim’s symptoms or from
empty drug containers or house hold
chemicals or from evidence found on
the victim’s personal effects.
• After the toxicologist detects, identifies, and
quantifies a drug or poison, they must be
prepared to assess the substances toxicity.
• Toxicologist is directly dependent on input from
the attending physician, the medical examiner,
and police officers.
• once the drug has been found and identified, the
toxicologist needs to assess its influence on the
behavior of the individual. Factors that need to
be considered include•
age
•
physical condition
•
tolerance of the drug user
•
additive or synergistic effects provided by
the interaction of 2 or more drugs Ex.
Alcohol and barbiturates or narcotics are
potentially lethal combinations.
•
observations of the arresting officer or of the
medical examiner if the person is deceased
Toxicology Procedures
• 10mL of blood in airtight container
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Add anticoagulant (EDTA)
Add preservative (sodium fluoride)
Refrigerate
Analyze quickly!
• 2 consecutive urine samples
– Some drugs take a while to show up in urine
(1-3 days)
• Vitreous humor
• Hair samples
Toxicology Procedures
• Alcohol and cocaine normally account for
90% or more of the drugs encountered in a
typical toxicology lab.
• toxicologist must devise an analytical
scheme that will detect, isolate and
specifically identify a toxic substance.
•
a. selectively removes and isolates
drugs and other toxic agents from the
biological materials submitted as evidence.
•
b. determines if the drug is an acid or a
base.
• acid drugs are easily extracted an acidified
water solution. Basic drugs are removed
from a basic water solution.
More Analytical Tests
• screening tests are then performed
– immunoassay- based on specific drug
antibody reactions, able to detect minute
amounts of drugs in body fluids and
organs.
– gas chromatography
– thin layer chromatography
• confirmation tests are done last.
– gas chromatography- mass spectrometry- first the drug
mixture is separated by gas chromatography, then the
separated components enter the mass spectrometer
which bombards the gas with high energy electrons.
The gas components break into fragments and a
fragmentation pattern (mass spectrum) for each gas in
the sample is made. A unique fingerprint of the
components in the drug mixture is created this way.
Creates a fingerprint for the drug
More Analytical Tests
• examples of applications• urine testing for drugs by the military
• heavy metal poison detection- heavy metals
include arsenic, antimony, bismuth, mercury, and
thallium.
• Reinsch test- dissolve suspected body fluid or
tissue in hydrochloric acid and then insert a
copper strip into the solution. The appearance of
a silvery or dark coating on the copper indicates
the presence of a heavy metal.
• application of an analytical technique for
determining inorganic compounds.
More Analytical Tests
• Carbon monoxide poison detection- 2 basic
methods-spectrophometric methods- examine the visible
spectrum of blood to determine the relative
amounts of carboxyhemoglobin to
oxyhemoglobin or total hemoglobin.
-gas chromatography- blood is treated with a
reagent that liberates the carbon monoxide and
then the CO amount is determined using gas
chromatography.
-Inhalation of CO fumes is a common way to
commit suicide.
-Level of CO in the blood of a victim found at the scene of
a fire is used to determine if foul play has occurred. If the
victim has high levels of CO in the blood, this proves that
the victim breathed the combustion products of the fire and
was therefore alive when the fire began. Many attempts at
covering up a murder by setting fire to the victim’s house
or car have been uncovered in this manner.
Carbon Monoxide
Poisoning
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- (95-98%) in liver by alcohol
dehydrogenase—turned into carbon dioxide
and water
– Excreted- (3-5%) by breath, perspiration, and
kidneys— eliminated unchanged. Amount of
alcohol in breath is directly proportional to
concentration of alcohol in blood (Brain)
Factors that Affect Alcohol
Absorption
• Time of
consumption
• Type of alcoholic
beverage
• Presence of food
in stomach
• Amount of
alcohol
Toxicology of Alcohol
• Alcohol intoxication depends on
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Amount of alcohol consumed
Time of consumption
Body weight
Rate of alcohol absorption
blood-alcohol concentration may not be
reached until 2-3 hours have elapsed
from the time of consumption. Normally
however, it takes 30-90 minutes from the
time of the final drink until absorption is
completed.
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 has its principle effect on the
central nervous system in particular,
the brain.
Blood-alcohol concentration is directly proportional to the
concentration of alcohol in the brain. (blood can be
readily tested, brain tissue cannot)
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
Alcohol in the Circulatory
System
• 20% of alcohol is absorbed through the
stomach wall into the portal vein. The rest
of the alcohol is absorbed through h the
small intestinal wall into the hepatic vein.
Both veins carry the alcohol to the liver,
where the process of alcohol destruction
begins.
• After the blood passes out of the liver, it
travels to the heart and over to the lungs
for gas exchange. As CO2 leaves the
blood and enters the alveoli, alcohol
leaves too.
Circulation and Alcohol
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.
• Henry’s Law applies here- When alcohol
is dissolved in blood, and is brought to
equilibrium with alveolar air, there is a
fixed ratio between the concentration of
the alcohol in air and its concentration in
the blood, and this ratio is constant for a
given temp. (At 34◦ C- 1 ml of blood will
contain the same amount of alcohol as
2100 ml of alveolar
Circulation of Alcohol
• After the blood leaves the lungs, it travels back
to the heart and then to the through the arteries
to the body, void of CO2 and rich with O2.
• The arteries subdivide into capillaries where gas,
nutrient and waste exchange occurs between the
body cells and the blood. The capillaries rejoin to
form veins which eventually lead back to the
heart completing the cycle.
• Concentration of alcohol in the arterial blood will
be considerably higher than concentration of
alcohol in the venous blood due to the rapid
diffusion of alcohol into the body tissues from the
venous blood during early stages of absorption.
Circulation of Alcohol
• Blood tests for alcohol take blood from veins,
which tend to have a lower alcohol content if the
person is still in the absorptive stage.
• Breath tests obtained during the absorptive
phase reflect the alcohol concentration in the
pulmonary artery and will show a greater alcohol
content than results would show from analysis of
venous blood.
• Once absorption is complete the difference
between a blood test and a breath test in terms
of alcohol content are minimal.
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- developed in
1954 by R.F. Borkenstein
• The Breathalyzer is a device for collecting
and measuring the alcohol content of
alveolar breath.
The Breathalyzer
•
•
When the valve is in the TAKE position, the
subject is required to blow into a mouthpiece
that leads into a metal cylinder. The pressure
of the breath raises a piston. As the breath
ends, the piston settles to a position that traps
the last portion of air.
When the valve is in the ANALYZE position,
the piston drops causing the sample of air to
pass into a glass ampoule that contains
potassium dichromate and silver nitrate in
sulfuric acid and water. Alcohol present will
dissolve in the dichromate solution, and be
oxidized to acetic acid. The potassium
dichromate will be destroyed in the process
making the solution clears. It is the amount of
destruction of the potassium dichromate
that is measured. This gives an indirect way
of measuring the original amount of alcohol
in the breath.
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
water
• The Breathalyzer is a simple spectrometer that 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
•
•
It is the amount of destruction of the
potassium dichromate that is
measured. This gives an indirect way
of measuring the original amount of
alcohol in the breath.
The Breathalyzer is a simple
spectrophotometer that indirectly
measures the quantity of alcohol
consumed by measuring the
absorption of light passing through
the potassium dichromate solution at
a given wavelength before and after
its reaction to alcohol.
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
•
Driver has a choice
of either submitting
to a test for alcohol
intoxication if
requested, or be
subject to loss of the
license for a
designated period,
usually 6 months to
one year.
France, Germany, Ireland,
or Japan (0.05%)
Sweden (0.02%)
Alcohol and the Law
• Try the drink wheel:
http://www.intox.com/wheel/drinkwheel.asp
Analysis of Blood for
Alcohol
• Gas chromatography- by comparing
the resultant alcohol peak area to
those obtained with known blood
alcohol standards, the investigator
can calculate the amount of alcohol
in the blood with high accuracy
Collection and Preservation
of Blood
• Blood must be drawn under medically
accepted conditions using a sterile needle
or lancet and a nonalcoholic disinfectant.
• Preservation is accomplished by sealing
the blood in an airtight container after an
anticoagulant (EDTA) and a preservative
(sodium fluoride*) have been added.
Specimen is then placed in a refrigerator.
• Testing of blood should not be delayed as
longer storage times reduce alcoholblood levels.