BSFS Forensic Chemistry and Toxicology 2 — Questions and Answers
Question 1: Which type of drug test is considered confirmatory rather than presumptive in forensic toxicology?
- Mass spectrometry (Correct answer)
- Immunoassay
- Color spot test
- Thin-layer chromatography
Correct answer: Mass spectrometry
Mass spectrometry provides definitive molecular identification and is accepted as a confirmatory test, whereas immunoassays are screening tools with higher false-positive rates.
Question 2: The legal blood alcohol concentration (BAC) limit for driving in most U.S. states for adults is:
- 0.08% (Correct answer)
- 0.05%
- 0.10%
- 0.02%
Correct answer: 0.08%
The per se legal limit for DUI in all 50 U.S. states is 0.08% BAC for drivers aged 21 and older.
Question 3: Which enzyme is primarily responsible for metabolizing alcohol (ethanol) in the liver?
- Alcohol dehydrogenase (ADH) (Correct answer)
- Acetylcholinesterase
- Cytochrome P450 only
- Monoamine oxidase
Correct answer: Alcohol dehydrogenase (ADH)
Alcohol dehydrogenase is the primary hepatic enzyme that converts ethanol to acetaldehyde in the first step of ethanol metabolism.
Question 4: Postmortem redistribution of drugs is a concern in forensic toxicology because it can:
- Cause drug concentrations to increase or change after death, complicating interpretation (Correct answer)
- Always reduce drug concentrations to zero
- Only affect alcohol levels
- Improve the accuracy of blood drug measurements
Correct answer: Cause drug concentrations to increase or change after death, complicating interpretation
After death, drugs can migrate from organs with high concentrations into blood, making postmortem drug levels unreliable if not collected from the correct site promptly.
Question 5: The Scott test is a presumptive field test used specifically for identifying:
- Cocaine (Correct answer)
- Heroin
- Cannabis
- Methamphetamine
Correct answer: Cocaine
The Scott test uses cobalt thiocyanate reagent and turns blue in the presence of cocaine, serving as a presumptive field identification test.
Question 6: In forensic chemistry, a 'blank' sample is used during analysis to:
- Detect and correct for contamination or background signals in the analytical process (Correct answer)
- Serve as a positive control for known substances
- Calibrate the mass spectrometer to known masses
- Simulate the unknown sample's matrix
Correct answer: Detect and correct for contamination or background signals in the analytical process
A blank sample contains no analyte and is processed identically to real samples to identify any contamination or background interference in the method.
BSFS Forensic Chemistry and Toxicology 2
Which type of drug test is considered confirmatory rather than presumptive in forensic toxicology?