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Forensic Analysis Units

Toxicology Unit

The Toxicology Unit identifies and quantifies (determines the amounts of) drugs, alcohols, and poisons in biological samples such as blood, urine, or tissue. The information is used by law enforcement and the courts to help determine if laws have been broken and/or if criminal charges are warranted. For instance, when there is cause to believe that a person may have been under the influence of alcohol and/or drugs, blood and urine samples are submitted for analysis. Forensic toxicologists also assist in postmortem investigations to establish the cause or circumstances of death.

Toxicology testing can be as routine as a single blood alcohol test or as complex as determining concentrations of a half dozen drugs and their metabolites in a single sample. The level of testing depends on the case and the type(s) of sample(s) submitted.

In order to perform analysis, the drug(s) or chemical(s) generally must first be extracted from the biological component of the sample. This extraction is accomplished using various chemical solvents followed by back extraction clean-up. Internal standards are added to the sample to document an adequate recovery of the drug (if present).

Available Toxicology Tests

Common Analytes

Ethyl Alcohol (alcohol) The determination of alcohol concentration is the most commonly performed analysis in the forensic toxicology unit. Microdiffusion is used to screen for oxidizable volatiles (a class of compounds that includes alcohol). Identification and quantitation of ethanol are performed using gas chromatography.

Cocaine The enzyme immunoassay (EIA) procedure detects both cocaine and its metabolite benzoylecgonine. Positive samples are then quantitated for both parent cocaine and metabolite benzoylecgonine, using gas chromatography/mass spectrometry (GC/MS).

Cocaethylene It is unique in that it is produced only in the presence of ethyl alcohol and cocaine. It crosses the blood-brain barrier easily and its concentration in the brain equals that of cocaine. Positive samples are quantitated and confirmed using GC/MS.

Cannabinoids. THC (delta-9-tetrahydrocannabinol) the active ingredient in marijuana is converted to 11-hydroxy-THC and then to 11-carboxy-THC. Blood is tested by the EIA procedure and confirmed with GC/MS.

Opiates These include heroin, morphine, codeine, methadone, oxycodone, hydromorphone and others. Morphine is formed as a metabolite of both heroin and codeine. The opiates are detected using EIA and GC/MS.

Benzodiazepines A class of compounds that include diazepam, alprazolam, and others. They are influenced by concomitant usage of other drugs, especially alcohol. The benzodiazepines are qualitatively detected using EIA. Quantitation is performed using high-pressure liquid chromatography (HPLC), gas chromatography (GC) and GC/MS techniques.

Summary

The responsibility of the forensic toxicologist lies in the preliminary screening, subsequent confirmation, and quantitation of all drugs in question. Only by following basic toxicological principles can accurate and reliable results be obtained and interpreted with confidence.

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