Fs Ch 11

Chapter 11

Forensic Toxicology

Forensic ScienceRichard Saferstein

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.2

Introduction Toxicologists -detecting and identifying:

-drugs/poisons-body fluids-tissues-organs

Major branch of forensic toxicology:-measurement of alcohol in the body




Toxicology of Alcohol Alcohol/ethyl alcohol (ETOH)

-colorless liquid consumed as a beverage.

-Depressant: effects the CNS/particularly the brain.




Alcohol Levels Blood:

-within minutes

-slowly increases in concentration

-maximum alcohol level is reached in the blood

-post-absorption period begins.

-alcohol concentration slowly decreases




Alcohol Levels

-Factors:

*consumption time

*the alcohol content

*amount consumed

*food present in the stomach determine the rate at which alcohol is absorbed.




Alcohol Levels Elimination:

-oxidation-liver-excretion-breath, urine, sweat

Extent of influence: Measuring-blood system-breath.

Experimental evidence:-amount exhaled=blood conetration




Alcohol & Circulatory System Closed circulatory system:

-heart/arteries/veins/capillaries.

Stomach-small intestines-blood stream-liver Blood (w/ETOH)-heart-lungs.

-carbon dioxide/alcohol leave the blood

-oxygen enters alveoli (air sacs).

-carbon dioxide/alcohol exhaled.




Breath Testers Many types of breath testers

-infrared light absorption

-exposed to infrared light.

-degree of the interaction of the light/alcohol

-gaining favor with police




Field Testing Field Sobriety tests: (FSTs)

-walk and turn-one-leg stand -alphabet -horizontal gaze nystagmus (HGN)-handheld breathalyzers -establish probable cause of impairment




Gas Chromatography Testing

Gas chromatography:

-most widely used approach-medically accepted conditions-qualified individual. -nonalcoholic disinfectant-proper storage:-airtight container-anticoagulant/preservative -refrigerate




Alcohol and Law AMA/National Safety Council:

-uniform and reasonable History:-1939 to 1964 =0.15 percent -1965=0.10-1972=recommended 0.08-2000-0.08 for all states (by 2004)




Alcohol and Law Implied Consent Law: -1973/ all states-DL stipulations-refusal to submit=loss of license-vary by state-Forced blood draw?




Role of the Toxicologist Drugs/poisons-body fluids-organs

Supportive evidence -symptoms-postmortem exam-scene evidence

No one test for all -general screening procedures-hope/1000’s to 1




Role of the Toxicologist Problem:

-concentration levels

-body=active chemistry laboratory

-assess the toxicity




The Analytical Scheme Scheme:

-detect

-isolate

-specifically identify

Drug extraction:

- acidic or basic.

- Screening/confirmation.




The Screening Step

Screening test: -quick insight-presence of a drug substance -+ results (tentative)-confirmation test-thin-layer chromatography-gas chromatography-immunoassay.




The Confirmation Step Gas chromatography/mass

spectrometry:

-test of choice.-GC: separates the sample into its

components-MS: unique “fingerprint” pattern-extracted/identified-opinion to effect on person’s physical

state.




Detecting Drugs in Hair Drugs:

-diffuse through the capillary walls-base of the hair-permanently in hair’s protein -hair grows-historical marker-1cm/month=timeline -problem: -environmental exposure-sweat




Nondrug Poisons Heavy metals: Rarely encountered-arsenic-bismuth-antimony-mercury Carbon monoxide:-most common-spectrophotometric-measure carboxyhemoglobin to total hemoglobin-gas chromatography.




Significance of Findings Found and identified:

-assesses influence

-blood concentration levels

-observations by PO

-motor skills/behavior




The Drug Recognition Expert (DRE) Program

Drug Recognition Experts (DRE)

-LAPD (1970’s)-clinical/psychological -ID/Differentiate -3-5 month training -standardized methods (court)




The DRE- Drug Influence Evaluation form

- cannot specify drug

- DRE data/forensic toxicologist

- Drug intoxication

Fs Ch 11

Technology

Transcript of Fs Ch 11