10 toxicology

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Forensic Toxicology

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Page 1: 10 Toxicology

Forensic Toxicology

Page 2: 10 Toxicology

Forensic Toxicology

Is defined as the science of detecting and identifying the presence of drugs and poisons in body fluids, tissues, and organs.

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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)

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Toxicology Procedures

10mL of blood in airtight containerAdd anticoagulantAdd preservative

2 consecutive urine samplesSome drugs take a while to show up in urine (1-3 days)

Vitreous humor

Hair samples

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Toxicology Procedures

Screening- quick test to narrow down possibilitiescolor tests, TLC, GC, immunoassay

Confirmation- determines exact identityGC/Mass SpectrophotometerNote: TLC—thin layerchromatography GC – Gas Chromatography

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Color Tests

Marquis Test: Turns purple in the presence of Heroin, morphine, opium Turns orange-brown in presence of Amphetamines

Scott Test: Three solutionsBlue then pink then back to blue in the presence of Cocaine

Duquenois-Levine: Test for marijuana –turns purple

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Drug Schedules

• Schedule I: • Drugs with high potential for abuse and

addiction, NO medical valueEx: Heroin, LSD, Ecstasy, Marijuana

• Schedule II: • Drugs with high potential for abuse and

addiction, have some medical value with restrictionsEx: PCP, Cocaine, Amphetamines, Most Opiates, Some Barbiturates

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Drug Schedules

• Schedule III: • Drugs with less potential for abuse and

addiction, currently acceptable for medical useEx: Some Barbiturates, Codeine, Steroids

• Schedule IV: • Drugs with low potential for abuse and

addiction, currently acceptable for medical useEx: Tranquilizers like Valium, Xanax, Librium

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Drug Schedules

• Schedule V:

• Drugs with low potential abuse, medical use, lowest potential dependency

• Ex: Some Opiates with Non-Narcotic Ingredients

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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

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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

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Factors that Affect Alcohol Absorption• Time of

consumption• Type of alcoholic

beverage• Presence of food

in stomach

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Toxicology of Alcohol

• Alcohol intoxication depends on– Amount of alcohol consumed– Time of consumption– Body weight– Rate of alcohol absorption

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Fate of Alcohol

• Alcohol is absorbed into the bloodstream

• Distributed through-out the body’s water

• And finally eliminated by oxidation and excretion

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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

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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

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Circulation and Alcohol

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Circulation and Alcohol

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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

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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.

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Analysis of BAC

• Breath Tests

• Field Sobriety Tests

• Blood Tests

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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.

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The Breathalyzer

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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.

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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

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• 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

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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.

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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

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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.

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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

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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.

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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.

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Field Sobriety Tests

• Horizontal Gaze Nystagmus– Involuntary eye jerk as eye moves horizontally

• Walk and Turn (divided attention tasks)• One-Leg Stand

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Parts of the brain affected by Alcohol• Alcohol 1st

affects the forebrain and moves backward

• Last affected is medulla oblongata

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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%)!

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Alcohol and the Law

• Try the drink wheel: http://www.intox.com/wheel/drinkwheel.asp

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The End