Physical Evidence Handbook

Toxicology Unit

Toxicology is the study of adverse effects of drugs and chemicals on living organisms. The discipline is divided into several major areas--Forensic, Clinical and Environmental. Forensic Toxicology applies toxicology to matters of law, to assist the courts in reaching verdicts that are in keeping with the facts. Put another way, forensic toxicology is involved with the medicolegal aspects of the use of drugs and chemicals that are harmful to man combining analytical chemistry and fundamental toxicology.

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:

  • Blood Alcohol
    • Screen, confirmation, and quantitation.
  • Drug Tests
    • Cocaine/Cocaine Metabolite
    • Opiates
    • Amphetamine/Methamphetamine
    • Marijuana/metabolites
    • Benzodiazepines
    • Phencyclidine
    • Lysergic Acid Diethylamide
    • Methadone
    • Zolpidem
    • Ketamine
    • Buprenorphine
    • Fentanyl
    • Oxycodone
    • Barbiturates
    • Gamma Hydroxybutyric Acid (GHB)
    • Basic Drug Screen
    • Acid/Neutral Drug Screen
  • Additional tests
    • Carbon Monoxide
    • Heavy Metals
    • Salicylates
    • Tampering
    • Acetaminophen
    • Phenothiazine drugs
    • Oxidizers
Common Analytes:

Ethanol (alcohol)
The determination of ethanol concentration is the most commonly performed analysis in the forensic toxicology unit. Identification and quantitation of ethanol are performed using dual column, headspace gas chromatography.

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

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 specimens are quantitated and confirmed using GC/MS.

THC (delta-9-tetrahydrocannabinol) the active ingredient in marijuana is metabolized to 11-hydroxy-THC and then to 11-carboxy-THC. Specimens are qualitatively screened by the EIA procedure and identified and quantified with GC/MS.

These include heroin, morphine, codeine, methadone, oxycodone, hydromorphone, oxymorphone and others. Morphine can also be formed as a metabolite of both heroin and codeine. The specimens are qualitatively screened by the EIA procedure and the opiates are identified and quantified with GC/MS.

A class of compounds that include diazepam, alprazolam, and others. Their effects are influenced by concomitant usage of other drugs, especially ethanol. The specimens are qualitatively screened using EIA. Quantitation of the benzodiazepines is performed using, gas chromatography (GC) and GC/MS techniques.


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