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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
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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
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
Schedule V:
Drugs with low potential abuse, medical use, lowest potential dependency
Ex: Some Opiates with Non-Narcotic Ingredients
Role of the Toxicologist
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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
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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 (liquid in eyeball)
Hair samples
Screeningquick test to narrow down possibilities
color tests, TLC, immunoassay
Confirmationdetermines exact identity
GC/Mass Spec
Color Tests
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Marquis Test:
Turns purple in the presence of Heroin, morphine, opium
Turns orange-brown in presence of Amphetamines
Scott Test (cobalt thiocynate):
Blue then pink then back to blue in the presence of Cocaine
Duquenois-Levine:
Test for marijuana –turns purple
More Analytical Tests
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Microcrystalline Tests: Identifies drug by using chemicals that reacts to produce characteristic
crystals
Chromatography: TLC, HPLC and gas – separate drugs/tentative ID
Mass Spectrometry: chemical “fingerprint” no two drugs fragment the same
**Note: HPLC = high pressure liquid 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
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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
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Time of consumption
Type of alcoholic beverage
Presence of food in stomach
Alcohol intoxication depends on
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Amount of alcohol consumed
Time of consumption
Body weight
Rate of alcohol absorption
Fate of Alcohol
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Alcohol is absorbed into the bloodstream
Distributed through-out the body’s water
And finally eliminated by oxidation and excretion
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
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Measuring the quantity of alcohol in the blood system determines the degree to which someone
is drunk
Two methods of making this measurement
1. Measurement of alcohol content in blood
2. Measurement of alcohol in breath
Circulation: Alveoli—small sacs in lungs—exchange vapors between breath and blood
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 (blood alcohol level)
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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 traps 1/40 of 2100 mL of alveolar breath.
Since the amount of alcohol in 2100 mL of breath approximates the amount of alcohol in 1 mL of
blood—
the Breathalyzer in essence measures the alcohol concentration present in 1/40 of a mL of blood.
Once the alveolar breath is trapped it is allowed to undergo a chemical reaction.
Other Breath Tests
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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
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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
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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 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
1. Horizontal Gaze Nystagmus
2. Involuntary eye jerk as eye moves horizontally
3. Walk and Turn (divided attention tasks)
4. One-Leg Stand
Alcohol and the Law
1939-1964: intoxicated = 0.15% BAC
1965: intoxicated = 0.10% BAC
2003: intoxicated = 0.08% BAC
Alcohol and the Law