CFC Toxicology & Drug Analysis 3 — Questions and Answers
Question 1: Which specimen is most useful for determining drug exposure over a period of approximately 90 days?
- Blood
- Urine
- Hair (Correct answer)
- Oral fluid
Correct answer: Hair
Hair grows approximately 1 cm per month, and a 3 cm segment reflects roughly 90 days of drug exposure through incorporation during keratinization.
Question 2: In forensic cases involving suspected opioid overdose, which endogenous substance must be distinguished from exogenous morphine in hair testing?
- Codeine
- Heroin (diacetylmorphine) (Correct answer)
- Normorphine
- Hydromorphone
Correct answer: Heroin (diacetylmorphine)
The presence of 6-monoacetylmorphine (6-MAM), a unique heroin metabolite, distinguishes heroin use from endogenous morphine or poppy seed ingestion.
Question 3: The Widmark formula is used in forensic toxicology primarily to:
- Calculate the lethal dose of a poison
- Estimate blood alcohol concentration from ingested ethanol (Correct answer)
- Determine time of death from vitreous potassium
- Identify synthetic cannabinoids by mass spectrometry
Correct answer: Estimate blood alcohol concentration from ingested ethanol
The Widmark formula estimates BAC based on amount of alcohol consumed, body weight, and gender-based distribution factor (r).
Question 4: Which synthetic opioid has an analgesic potency approximately 100 times that of morphine and is frequently encountered in forensic drug casework?
- Tramadol
- Fentanyl (Correct answer)
- Oxycodone
- Buprenorphine
Correct answer: Fentanyl
Fentanyl is approximately 100 times more potent than morphine and is a leading cause of opioid overdose deaths in forensic casework.
Question 5: A urine specimen submitted for drug testing has a creatinine of 2 mg/dL and specific gravity of 1.001. The appropriate forensic interpretation is:
- The specimen is substituted or severely diluted (Correct answer)
- The specimen is adulterated with bleach
- The specimen tests positive for diuretics
- The specimen is valid but shows alcohol use
Correct answer: The specimen is substituted or severely diluted
Creatinine below 2 mg/dL and specific gravity of 1.001 or less meet federal criteria for a substituted specimen, indicating it is not consistent with normal human urine.
Question 6: Which class of drugs is detected by the EMIT immunoassay using a phencyclidine (PCP) antibody but may also cross-react with dextromethorphan?
- Dissociative anesthetics (Correct answer)
- Hallucinogens (LSD class)
- Synthetic cannabinoids
- Benzodiazepines
Correct answer: Dissociative anesthetics
Both PCP and dextromethorphan are NMDA receptor antagonists (dissociative agents), sharing enough structural similarity to cause cross-reactivity in PCP immunoassays.
Question 7: What does the term 'chain of custody' ensure in forensic toxicology sample handling?
- Sample is stored at the correct temperature
- Sample integrity and documented accountability from collection to court (Correct answer)
- All laboratory staff are certified to handle the sample
- The sample is tested within 24 hours of collection
Correct answer: Sample integrity and documented accountability from collection to court
Chain of custody documents every person who handled the specimen, maintaining an unbroken record of accountability that ensures evidentiary integrity in court.
CFC Toxicology & Drug Analysis 3
Which specimen is most useful for determining drug exposure over a period of approximately 90 days?