Forensic toxicology drug testing methods, chain of custody concepts, and postmortem toxicology considerations.
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- What is the purpose of maintaining chain of custody for a forensic toxicology specimen?
- To document every person who handled the specimen, ensuring it was not tampered with and can be legally admissible as evidence
- What information must typically be recorded each time a specimen changes hands in chain of custody documentation?
- Who transferred it, who received it, and the date and time of transfer
- What initial screening method is commonly used in drug testing due to its speed and low cost, despite lower specificity?
- Immunoassay screening
- What confirmatory testing method is considered the gold standard for identifying a specific drug due to its high specificity?
- Gas chromatography-mass spectrometry (GC-MS)
- Why must a positive immunoassay screening result generally be confirmed before being reported as a true positive?
- Immunoassays can cross-react with structurally similar substances, producing false positive results
- What term describes the minimum drug concentration required for a specimen to be reported as positive on a test?
- The cutoff concentration
- What is postmortem redistribution in forensic toxicology?
- The phenomenon where a drug's concentration changes after death as it moves between tissues and blood compartments, complicating interpretation
- Why is central blood (such as heart blood) less reliable than peripheral blood for postmortem drug concentration measurement?
- Central blood is more affected by postmortem redistribution from nearby drug-containing organs like the liver
- What eye fluid specimen is commonly used in postmortem toxicology because it resists decomposition and contamination longer than blood?
- Vitreous humor
- What specimen type provides the longest window of detection for drug use history, often spanning weeks to months?
- Hair
- What specimen type is most commonly used for workplace drug testing due to ease of collection and established cutoff standards?
- Urine
- What five drug classes are traditionally included in the standard SAMHSA workplace drug testing panel?
- Marijuana metabolites, cocaine metabolites, opiates, amphetamines, and phencyclidine (PCP)
- What is the primary inactive urinary metabolite tested for to detect marijuana use?
- THC-COOH (11-nor-9-carboxy-THC)
- What is the primary urinary metabolite tested for to detect cocaine use?
- Benzoylecgonine
- What term describes attempts to alter, dilute, or substitute a urine sample to evade detection of drug use?
- Specimen adulteration
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