1. Chapter 6:
Forensic Toxicology

2. Forensic Toxicology
Detect & identify drugs and poisons in body fluids, tissues & organs
U.S. alcohol related
40% of all traffic deaths
17,500 fatalities and more than 2 million injuries

3. Metabolism of Alcohol
Metabolism – chemical reactions that occur within the body to transform chemicals into other chemicals
3 steps:
Absorption
Distribution
Elimination

4. Absorption & Distribution of Alcohol
Occurs in stomach & small intestines
Enters blood stream within minutes of consumption
20% absorbed in stomach & 80% in intestines
Spreads equally through tissues with high water content
Fat, bones and hair have low water content

5. Factors affecting absorption
Total time taken to consume the drink
Alcohol content of drink
Amount of drink consumed
Quantity and quality of food in stomach

6. Elimination of Alcohol
2 mechanisms:
1. Oxidation
98% oxidized into CO2 and water
Occurs in liver where enzymes break it down
2. Excretion
Released unchanged through breath, urine & perspiration
Elimination occurs at an average rate of about 0.015% per hour

7. Blood Alcohol Concentration
Brain
Best tissue for determination
Unrealistic in most situations
Blood
Provides medium for circulating alcohol all over body
Blood-alcohol concentrations are directly proportional to the concentration of alcohol in the brain.

8. Chemistry Check-up Henry's Law: More pressure will dissolve more gas
Gases dissolved in a liquid will escape into the surrounding air when pressure of the air is less than that of the liquid

9. Relationship between Blood and Breath
Based on Henry’s Law
Alcohol content:
2,100 mL of alveolar breath = 1 mL of blood
80 mg of alcohol in 100 mL of blood is equivalent to 80 mg of alcohol in 210,000 mL of breath. (210 Liters)
Alveoli are the air sacs in the lungs where gas exchange takes place.

10. Testing for Intoxication
Breath testing
Widespread, reliable, rapid & practical
Uses deep lung breaths
Measures alcohol concentration in pulmonary artery
Breathalyzer
Developed by Borkenstein in 1954
Basically a spectrophotometer
Used a toxic chemical called potassium dichromate
Modern day breath testers
Free of chemicals
Produces electrical current proportional to alcohol content

11. Field Sobriety Testing
Used to determine suspect’s physical impairment and justify need for breath analysis
Horizontal-gaze nystagmus – involuntary jerking of the eye as it moves to the side
Walk, turn and stand on one leg – 9 steps heal-to-toe and balance for 30 seconds while counting out loud

12. Blood Analysis for Alcohol
2 procedures:
Gas chromatography
Spectrophometry – used more in clinical/hospital settings
Collection & preservation techniques are important
Nonalcoholic disinfectant used
Airtight container
Add anticoagulant & preservative
Keep refrigerated
Blood not refrigerated, left to long, or lacking preservative results in a decrease in blood-alcohol levels.

13. Alcohol and the Law 2000 Federal Law Other countries
0.08% legal limit for noncommercial drivers
0.04% legal limit for truck and bus drivers
Old limits 0.15%
Other countries
Sweden has lowest legal limit – 0.02%
Finland, France, Germany, Ireland, Japan, Netherlands, & Norway – 0.05%
Canada, Italy, Switzerland, and United Kingdom – 0.08%
Automobile accidents
4X more likely with 0.08% level
25X more likely with 0.15% level

14. Constitutional Issues
Implied Consent Law – driver can either submit to an intoxication test or lose license for a designated period (usually 6 months)
Supreme Court
Ruled that 5th amendment rights applied only to testimonial evidence NOT physical evidence.
Obtaining blood samples from intoxicated suspect is an emergency situation and does NOT require a warrant.

15. Challenges in Toxicology
Concentration levels of only micrograms or nanograms
Chemical alteration of the substance by body metabolism
Example: Heroin is metabolized into morphine which then bonds to carbohydrates before it is eliminated in the urine.

16. Toxicology Testing
When possible both blood and urine samples should be obtained.
Over 90% of drugs analyzed is alcohol, marijuana, or cocaine.
Must first isolate then identify substance.
Recovery/Isolation of the substance is based on pH

17. Screening vs. Confirmation
Screening allows examination of a large number of specimens in a short time period and for a wide range of drugs.
Thin-layer chromatography
Gas chromatography
Immunoassay – drug antibody reaction
Confirmation identifies the specific drug
Mass spectrometry

18. Hair Drug remain in Bloodstream – about 24 hours
Urine – up to 72 hours
Hair – permanently entrapped
Drugs from the blood will diffuse into the root of the hair and become entrapped in the proteins of the hair.
Hair provides a “time line” of drug use.

19. Heavy Metals Once popular in murder cases but rare today
Heavy metals include
Arsenic
Reinsch test
Bismuth
body fluid or tissue is dissolved in HCl and a copper strip is inserted
Antimony
Mercury
Thallium
Dark or silvery coating on copper strip indicates presence of heavy metal

20. Carbon Monoxide
Carbon Monoxide takes the place of oxygen in bonding to hemoglobin in blood stream
2 tests: Gas chromotography & Spectrophotometry
Toxic levels can be obtained in 5-10 minutes within a closed single car garage
Presence of in bloodstream of a victim involved with a fire can indicate foul play
CO present - person alive during fire
CO not present - person already dead

21. Toxicological Findings
Toxicologist must assess the influence of drugs found on behavior of individual
Must consider
Age
Physical condition
Tolerance of drug user
Individual’s history of drug use
Additive/synergistic effects of two or more drugs