BSFS Forensic Chemistry and Toxicology 1 — Questions and Answers
Question 1: Which analytical technique is most commonly used in forensic labs to identify unknown substances by separating and detecting components in a sample?
- Gas chromatography-mass spectrometry (GC-MS) (Correct answer)
- Infrared spectroscopy only
- UV-Vis spectrophotometry only
- Nuclear magnetic resonance only
Correct answer: Gas chromatography-mass spectrometry (GC-MS)
GC-MS is the gold standard for forensic substance identification because it combines separation power with definitive molecular identification.
Question 2: In forensic toxicology, which specimen is preferred for detecting long-term drug use history over several months?
- Hair (Correct answer)
- Urine
- Blood
- Saliva
Correct answer: Hair
Hair retains drug metabolites incorporated during growth, allowing detection of drug use for up to 90 days or longer depending on hair length.
Question 3: The presumptive color test that turns purple/blue in the presence of opioids is known as the:
- Marquis test (Correct answer)
- Scott test
- Duquenois-Levine test
- Cobalt thiocyanate test
Correct answer: Marquis test
The Marquis reagent reacts with opioids to produce a characteristic purple-to-blue color, serving as a rapid field presumptive test.
Question 4: Which term describes the process by which the body eliminates a drug, typically through metabolism and excretion?
- Elimination (Correct answer)
- Absorption
- Distribution
- Biotransformation
Correct answer: Elimination
Elimination refers to the combined processes of drug metabolism and excretion that remove a substance from the body.
Question 5: In arson investigation, which chemical class of accelerants is most commonly detected using GC-MS?
- Petroleum distillates (Correct answer)
- Alcohols
- Ketones
- Aldehydes
Correct answer: Petroleum distillates
Petroleum distillates such as gasoline, kerosene, and lighter fluid are the most frequently encountered accelerants in arson cases and are reliably detected by GC-MS.
Question 6: The chain of custody in forensic toxicology is maintained primarily to:
- Ensure evidence integrity and admissibility in court (Correct answer)
- Speed up laboratory analysis
- Reduce the cost of testing
- Allow multiple labs to share samples simultaneously
Correct answer: Ensure evidence integrity and admissibility in court
Maintaining an unbroken chain of custody documents every person who handled the evidence, ensuring it has not been tampered with and is legally admissible.
BSFS Forensic Chemistry and Toxicology 1
Which analytical technique is most commonly used in forensic labs to identify unknown substances by separating and detecting components in a sample?