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?
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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?
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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?
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Immunoassay screening- What confirmatory testing method is considered the gold standard for identifying a specific drug due to its high specificity?
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Gas chromatography-mass spectrometry (GC-MS)- Why must a positive immunoassay screening result generally be confirmed before being reported as a true positive?
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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?
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The cutoff concentration- What is postmortem redistribution in forensic toxicology?
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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?
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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?
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Vitreous humor- What specimen type provides the longest window of detection for drug use history, often spanning weeks to months?
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Hair- What specimen type is most commonly used for workplace drug testing due to ease of collection and established cutoff standards?
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Urine- What five drug classes are traditionally included in the standard SAMHSA workplace drug testing panel?
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Marijuana metabolites, cocaine metabolites, opiates, amphetamines, and phencyclidine (PCP)- What is the primary inactive urinary metabolite tested for to detect marijuana use?
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THC-COOH (11-nor-9-carboxy-THC)- What is the primary urinary metabolite tested for to detect cocaine use?
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Benzoylecgonine- What term describes attempts to alter, dilute, or substitute a urine sample to evade detection of drug use?
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Specimen adulteration
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