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The Truth About Toxicology Tests

Facts about 'real-life' toxicology tests you won't learn from watching television crime shows.

How are forensic toxicology tests done? continued...

The tissue and fluid collection is typically done by a pathologist or morgue assistant, Robin says, and the process usually takes just 15 or 20 minutes.

Next, the specimens are turned over to a toxicology expert for testing. Testing is typically done by medical technologists or chemists, such as forensic chemists with doctoral training who are certified by The American Board of Clinical Chemistry or the American Board of Forensic Toxicology, according to the College of American Pathologists.

Medical examiner office personnel can also conduct toxicology drug testing related to an autopsy. Toxicology drug testing laboratories where the analyses are carried out are accredited by such organizations as the College of American Pathologists or state health departments or other organizations, to ensure uniform quality standards.  

''The tissue is placed in special containers that prevent contamination of the tissue,'' Robin says.  Preservatives can help prevent or delay breakdown of the drugs in the samples, Magnani says.

A ''paper trail'' records exactly who has handled the specimens to reduce the chance of contamination or mix-ups.

Just as important as the collection and tracking of fluid, blood, and tissue samples is the field investigation, Robin says. That involves officials looking into the medicine cabinet and around the home of the deceased person for drugs he or she may have been taking, including prescription drugs, over-the-counter medicines, and illicit drugs.

That search could also turn up evidence that a person was getting prescriptions from several doctors.

Who interprets forensic toxicology tests, and how?

Toxicologists, chemists, and pathologists  all need to be involved to correctly interpret results.  

''The first thing we would do is a basic screen for drugs in the urine and in the blood," Magnani says. The search would be for drugs such as opiates, amphetamines, marijuana, alcohol, and barbiturates, she says.

The basic toxicology screen typically uses an immunoassay, Robin says. This type of test looks for drugs in the blood using specific antibodies that detect various classes of drugs.

If something shows up, a more sophisticated test is done, using techniques such as mass spectrometry, which can identify chemicals in substances by their mass and charge.

"These confirmatory methods are actually more sensitive," Robin says. "You can find lower quantities [of the substance]."

The more sophisticated tests can tell experts the exact concentration of the drug or other substance, says Hall, who is also clinical assistant professor of public health at Weatherford College in Weatherford, Texas.

Experts also can determine if two drugs found together may have had a synergistic effect -- which happens when two drugs similar in their actions produce an exaggerated effect when taken together. It's akin to ''one plus one equals five," Robins says.

Experts have to determine if the drug or other substances found in the specimens are a therapeutic dose, a toxic dose, or a lethal dose -- whether they contributed to the death or caused the death.

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