Forensic toxicology
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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

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Forensic Toxicology

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Forensic toxicology

Forensic Toxicology


Forensic toxicology1

Forensic Toxicology

  • Definition:

  • The science of detecting and identifying the presence of drugs and poisons in body fluids, tissues, and organs.


Controlled substances act

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

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

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 procedures1

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


Forensic toxicology

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

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

Factors that Affect Alcohol Absorption


Toxicology of alcohol1

Toxicology of Alcohol

  • Alcohol intoxication depends on

    • Amount of alcohol consumed

    • Time of consumption

    • Body weight

    • Rate of alcohol absorption


Fate of alcohol

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

Fate of Alcohol Con’t

Note:

  • Oxidation is the combination of oxygen and alcohol to produce new products by the liver

  • Elimination is removing alcohol from the body in an unchanged state; normally excreted in breath and urine


Alcohol in the circulatory system

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 and Alcohol


Circulation definitions

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

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

Analysis of BAC

  • Breath Tests

  • Field Sobriety Tests

  • Blood Tests


Breath tests

Breath Tests

  • A breath test reflects the alcohol concentration in the pulmonary artery.

  • One instrument used for breath tests is called TheBreathalyzer.

  • The Breathalyzer is a device for collecting and measuring the alcohol content of alveolar breath.


The breathalyzer

The Breathalyzer


The breathalyzer con t

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

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

  • 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

Potassium dichromate

Ethyl alcohol

Sulfuric acid

Chromium sulfate

Potassium sulfate

Acetic acid

Dihydrogen oxide


Other breath tests

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

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

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

Infrared and Fuel Cell Breath Tests


Field sobriety testing

Field Sobriety Testing

  • Two reasons for the field sobriety test:

    • Used as a preliminary test to ascertain the degree of the suspect’s physical impairment

    • To see whether or not an evidential test is justified.


Field sobriety testing methods

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

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

Parts of the brain affected by Alcohol


Alcohol and the law

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 law1

Alcohol and the Law

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


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