10.7 Notes

1. 10.7 Notes Toxicologists & Drug Analysis

2. Objectives • Describe techniques that forensics toxicologists use to isolate and identify drugs and poisons.

3. Screening Tests • Use TLC, GC, Immunoassay • Immunoassay – very different • Based on specific drug antibody reactions • Ability to detect small concentrations • Best for detecting marijuana

4. Confirmation Tests • GC/MS • One step test of unequaled sensitivity and specificity • Drug testing not related to criminal matters

5. Drugs in Hair • Drugs remain in • Bloodstream – 24 hours • Urine – 72 hours • Tested in Private labs, typical for workplace screenings • Hair nourished by blood flowing through capillaries near root • Drugs diffuse through capillary walls and become permanently entrapped in hair’s protein structure • Drug’s location becomes historical marker for delineating drug intake

6. Heavy Metals • Group of poisons • Arsenic, Bismuth, Antimony, Mercury, Thallium • Reinsch Test • Dissolve body fluid or tissue in hydrochloric acid solution then insert copper strip to solution • Appearance of silver or dark coating on copper indicates presence of heavy metal • Confirm with inorganic analysis

7. Carbon Monoxide • One of the most common poisons • Primarily absorbed by red blood cells • Combines with hemoglobin to form carboxyhemoglobin • Not enough hemoglobin left to carry oxygen to tissues • Causes asphyxiation

8. 2 Basic Methods for Detection of CO • Spectrophotometric – visible spectrum • GC – liberates CO from blood • Calculate percent saturation • Greater than 50-60% = fatal • Fatal levels can be lower when in combination with depressants

9. Arson Victim • High levels of carbon monoxide in blood indicate that victim breathed in products of fire and was alive when fire began • Low levels = dead before fire started • Could have been placed there to destroy evidence

10. Significance of findings • Interpreting results is the most difficult chore • Blood concentration levels can be used to estimate pharmacological effects of drugs

11. Significance of findings • Before drawing conclusions, toxicologists must consider other factors – age, physical condition, drug history, tolerance • Prolonged use can make an individual less responsive to drug’s effects • Additive or synergistic effects provided by interaction of 2 or more drugs

13. Concentration in urine is poor indicator because formed outside circulatory system and drug levels can build up over long periods of time • Drug can be found in urine 1-3 days after taken and long after other effects have disappeared • Best used to corroborate other findings

14. Drug Recognition experts (DRE) • 1970s, LAPD developed and tested clinical and psychophysical examinations that police officers could use to identify and differentiate between types of drug impairment • Evolved into national program • Standardized methods • Not a substitute for toxicology testing

15. 10.7 Questions • What is the difference between a screening test and a confirmation test? • What are the three screening tests most widely used for forensic toxicology? What is the confirmation test of choice? • Which of the following is not classified as a heavy metal? • Lead • Arsenic • Mercury • Thallium • Explain how inhaling carbon monoxide can cause death. • Name at least three factors in addition to blood concentration levels that must be considered before drawing conclusions about a subject’s drug induced behaviors. • Why is the concentration of a drug present in urine a poor indicator of how extensively an individual’s behavior or state is influenced by the drug?