Presentation on theme: "Toxicologists & Drug Analysis"— Presentation transcript:
1 Toxicologists & Drug Analysis 10.7 NotesToxicologists & Drug Analysis
2 ObjectivesDescribe 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 reactionsAbility to detect small concentrationsBest for detecting marijuana
4 Confirmation Tests GC/MS One step test of unequaled sensitivity and specificityDrug 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 screeningsHair nourished by blood flowing through capillaries near rootDrugs diffuse through capillary walls and become permanently entrapped in hair’s protein structureDrug’s location becomes historical marker for delineating drug intake
6 Heavy Metals Group of poisons Reinsch Test Arsenic, Bismuth, Antimony, Mercury, ThalliumReinsch TestDissolve body fluid or tissue in hydrochloric acid solution then insert copper strip to solutionAppearance of silver or dark coating on copper indicates presence of heavy metalConfirm with inorganic analysis
7 Carbon Monoxide One of the most common poisons Primarily absorbed by red blood cellsCombines with hemoglobin to form carboxyhemoglobinNot enough hemoglobin left to carry oxygen to tissuesCauses asphyxiation
8 2 Basic Methods for Detection of CO Spectrophotometric – visible spectrumGC – liberates CO from bloodCalculate percent saturationGreater than 50-60% = fatalFatal levels can be lower when in combination with depressants
9 Arson VictimHigh levels of carbon monoxide in blood indicate that victim breathed in products of fire and was alive when fire beganLow levels = dead before fire startedCould have been placed there to destroy evidence
10 Significance of findings Interpreting results is the most difficult choreBlood 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, toleranceProlonged use can make an individual less responsive to drug’s effectsAdditive 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 timeDrug can be found in urine 1-3 days after taken and long after other effects have disappearedBest 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 impairmentEvolved into national programStandardized methodsNot a substitute for toxicology testing
14 10.7 QuestionsWhat 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?LeadArsenicMercuryThalliumExplain 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?