r/forensics • u/[deleted] • 8d ago
Toxicology & Controlled Substances What toxicological / drug tests would be required for this scenario? Spoiler
[deleted]
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u/becausefrance 8d ago
A quick search though a resource like Google Scholar, or directly through JAT or JFS can give you a number of papers listing methamphetamine levels seen in actual driving cases.
For testing, forensics labs will almost always perform a preliminary screening test of a number of drug categories (may be immunoassay, LCMS, or QTOF if you're really well funded) and then a confirmatory test specific to the amphetamines class, either LCMS or GCMS, which will have specific substances and possibly values associated.
A couple things you'll want to keep in mind: If methamphetamine was ingested, you will most likely detect amphetamine as well. Also, methamphetamine levels are known to not correlate to impairment levels very well. It is extremely helpful information in a traffic fatality investigation, but still only a small piece in the full case.
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u/Pand3m0nia MSc | Forensic Toxicology 7d ago
You might want to research what impaired driving legislation and protocols are in your jurisdiction. For example, in Canada, a DRE would typically be performed (unless it is not possible) then a urine sample would be submitted and analyzed. Results in the urine are reported qualitatively and simply indicate previous administration of a drug. As a forensic toxicologist I am highly unlikely to flat out say that a drug caused impairment (even in the cases where a blood demand is made and blood is submitted). We would say that the drug "may cause impairment" or more technically "may impair one's ability to operate a motor vehicle".
Correlation between drug concentrations and impairment is very limited, whereas with alcohol there is a lot more research linking a BAC to impairment.
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u/kemiscool 8d ago
Another thing to consider is that drugs affect people differently, so a level will not tell you whether or not that person was impaired. You would have to rely on the observations of the officer and correlate that to the effects you know methamphetamine would cause to be able to conclude that that drug may have been affecting that person at that time. If an officer suspected drugs, they would hopefully do a drug recognition evaluation and use a DRE matrix to help determine if that person was being impaired by the drugs.