Download Notes: Toxicology

Forensic Toxicology
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Definition: The science of detecting and identifying the presence of drugs and poisons in body fluids, tissues, and organs.
Controlled Substances Act
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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
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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, Librium
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
Screening– quick test to narrow down possibilities
– color tests, TLC (thin layer chromatography), immunoassay
Confirmation– determines 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: Three solutions
– 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?
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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
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(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
Toxicology of Alcohol
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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
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
– Measurement of alcohol content in blood
– Measurement of alcohol in breath
Circulation Definitions
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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
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
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Breath Tests
Field Sobriety Tests
Blood Tests
Breath Tests
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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
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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:
2K2Cr2O7 + 3C2H5OH + 8H2SO4  2Cr2(SO4)3 + 2K2SO4 + 3CH3COOH + 11H2O
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
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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
Field Sobriety Testing Methods
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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.
Horizontal Gaze Nystagmus
• Involuntary eye jerk as eye moves horizontally
Divided attention tasks
• Walk and Turn
• One-Leg Stand
Parts of the brain affected by Alcohol
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Alcohol 1st affects the forebrain and moves backward
Last affected is medulla oblongata
Alcohol and the Law
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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%)!