The Toxicology Unit analyzes biological samples for the presence of alcohol and drugs. Blood, urine, or tissue samples are collected from subjects who have been charged with driving while intoxicated, victims of poisoning or sexual assault, from medical examiners’ offices, or in other suspicious or unusual circumstances. The samples are received and cataloged, and all information about the case is noted.

Samples are first analyzed for alcohol by a technique called headspace gas chromatography. This technique is extremely accurate and sensitive and is the standard procedure for alcohol and volatile compound analysis in the field of forensic toxicology.

If an agency requests that a sample be analyzed for the presence of drugs, further tests are performed. The sample is first screened using a technique called fluorescence polarization immunoassay (FPIA), which tells whether certain types of drugs (such as amphetamines or opiates) are present or absent. If the sample is positive, it is further analyzed using a more specific and sensitive method called gas chromatography/mass spectrometry (GC/MS). This technique produces a molecular "fingerprint" or mass spectrum, unique to each drug. The analyst uses the spectrum to make a positive identification of a compound in a sample. The Toxicology Unit can specify which drugs are present in a sample, even if the quantity is very small. The unit can identify most street drugs, prescription drugs, and over-the-counter drugs, in addition to carbon monoxide in the blood of fire victims, inhalants, and alcohol content in unknown beverages and liquids. New analytical techniques are developed for new drugs when required.

The Toxicology Unit has a main laboratory in Lansing and a satellite laboratory in Marquette. The Lansing Laboratory handles alcohol cases from most of the Lower Peninsula and drug cases from the entire State of Michigan. The Marquette Laboratory analyzes alcohol cases for the Upper Peninsula. Nine forensic scientists analyze over 13,000 alcohol and 2,500 drug cases per year, in addition to providing court testimony on case results.