Forensic testing for the ingestion of poisons or drugs can be critical to a criminal investigation. While knowledge of toxic materials spans several centuries, the ability to test for these poisons systematically was not available until the early 20th century. Today, forensic toxicology routinely involves alcohol and drug testing.
Toxicology in postmortem cases
A forensic toxicologist might get involved in a postmortem investigation if drug intoxication wasn't previously suspected, in drug-related homicides, or if either a suspect or the deceased might have been under the influence of drugs at the time of the fatal event. In some deaths, notably accidental and homicidal ones, drug testing may determine if impairment was a factor in the fatal incident.
Forensic toxicologists may not only perform comprehensive testing for drugs of abuse (including alcohol), but also therapeutic drugs. Alcohol testing is routinely performed in nearly all traumatic deaths, such as motor vehicle fatalities. Toxicology evaluations for therapeutic drugs may be important in confirming a death. One such example may involve measuring blood concentrations of anticonvulsant medicines in a person with seizures. If the deceased had been under-medicated or noncompliant with a treatment regiment, thus subject to a seizure episode, it relevance becomes an important contributing factor to the death.
Lab analysis of several different types of samples from decedents first requires separating the substance of interest from the body fluid or tissue sample before identifying substances with different tests. When the lab identifies tissue as positive for a particular substance, it must confirm results with a different and often more sensitive and specific technique. However, the presence of a particular substance doesn't mean it caused the death. The lab must determine the concentration present in the sample, and the forensic pathologist must interpret these data, along with the remaining autopsy findings, to make that determination.
Other uses of toxicology
While forensic toxicology often deals with postmortem specimens, it may also involve the living and issues related to drug toxicity. Testing not only includes investigations of driving under the influence of alcohol or drugs, but also testing for illicit performance-enhancing drugs in athletes and drug testing in the workplace.
Illicit drug use continues to be a big medical and social problem in the U.S. Members of the military, public sector employees, health care employees, transportation employees, and a growing number of private sector employees are often required to be drug tested before starting a new job or maintaining that job. Drug testing may also be required when securing new insurance policies. Prison populations may also be tested for illegal drug use, most frequently screening for the presence of amphetamines, marijuana, cocaine, phencyclidine (PCP), and/or opiates (morphine, heroin). Urine is still the most common testing source, but drug testing can also be done on blood, hair, sweat, and saliva.