1. Toxicologists & Drug Analysis
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 Reinsch Test
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

12. 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

13. 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

14. 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?