Toxicology Tests and Autopsies

A look into the complex process of forensic toxicology testing following an autopsy.

After the April 21 death of music legend Prince Rogers Nelson, questions are being asked as to why the autopsy report detailing his death has taken so long. The day after Prince passed, an autopsy was performed at the Midwest Medical Examiner’s Office in Ramsey, Minn., by A. Quinn Strobl, MD, FCAP, and a member of the College of American Pathologists (CAP). According to Strobl’s office, the autopsy was completed in four hours; however, it was announced that the results could take two to six weeks to be released.1 This isn’t the only scenario of a long-awaited autopsy report, but it has people asking again, why do they take so long? When there are no obvious signs of death, as in the case of Prince, a toxicology test is needed to determine the cause of death. Contrary to representations by TV crime shows, these tests are complex and can take several weeks to complete.

First of all, it is important to distinguish the different types of toxicology tests. “Hospital testing is a little bit different from medical examiner forensic pathology testing,” said Michael Bell, MD, chief medical examiner for Palm Beach County in West Palm Beach, Fla., and a member of the CAP. Hospital toxicology screenings are usually simple tests that look for the presence of drugs of abuse in the urine and, occasionally, the blood. Toxicology tests performed for autopsies are called forensic or post-mortem toxicology tests. These tests determine if and what kind of drugs were in a person’s system. Experts also measure the amount of drugs and look to see if the concentration is of a lethal dosage.

During an autopsy, a pathologist collects samples of blood, various tissues and, if present, urine. Usually, pathologists collect blood from multiple areas of the body. “We draw blood typically from a peripheral source, like the femoral vein,” Bell said. “We try to avoid taking it from the central parts of the body like the heart.” Bell explained that because of something called post-mortem redistribution, there may be differences in the concentration of the drug in different locations of the body.

Tissue samples might be taken from the liver, brain, spleen, kidney and the eyes. Sometimes a pathologist will take a sample from the contents of a person’s stomach and bile secreted by the liver. Once the samples are collected, they are tested by medical examiner personnel in laboratories that are accredited by the CAP or other organizations to maintain quality standards.

Pathologists, toxicologists and chemists work together during this process, which can involve several rounds of tests. The first tests are basic screens for drugs in the blood and urine, typically using an immunoassay. According to information provided by the CAP, this test utilizes specific antibodies that detect several classes of drugs such as opiates, amphetamines, marijuana, alcohol and barbiturates. If a drug is detected in the first test, scientists confirm the results by running more tests, which can take several more days and might have to be repeated to ensure accuracy.

A second and more complex test has to be performed if the presence of a drug is confirmed by the first round of tests. The CAP says this test may involve measurements of mass and other characteristics to detect chemicals in substances. This process can take several more days, depending on the complexity of the test and type of drug. Bell said, “Remember, there are thousands and thousands of drugs out there. Not all these drugs are screened for. Not all of the drugs are toxicology labs able to actually measure or quantitate.” Bell explained that many of the new designer drugs can be detected in the blood but cannot actually be measured. He added that it is not uncommon for samples to be sent to another lab that specializes in testing for specific drugs.

The process is lengthened if multiple drugs are detected in the person’s system, which usually involves added tests and calculations. Bell explained, “There are hundreds and thousands of different drug interactions. You have to find out what the drugs are and obviously look at how high the levels are and then look for any drug interactions.” This is a detailed process; ascertaining the exact levels of a single drug or multiple drugs, as well as how these drugs interact with each other, increases the time needed to complete the procedure.

Regarding the complexity of toxicology tests, Bell commented, “There are so many different drugs; none of them are screaming out their names. The methods are quite complex. While urine is a nice clean specimen to test, because it’s entirely fluid, blood itself is much more difficult to test because it’s not just fluid, there are also cells in it.” According to Bell, there has to be a certain amount of what’s called “cleaning up” the specimen before it can be tested in the machines. Bell added, “You don’t just inject it into a machine and then it spits out an answer. And nowadays nobody takes just one drug anymore. There are typically several drugs present. It becomes a much more complex process.” Bell mentioned that a typical time period for his lab to produce results is about a month, but it all depends on the amount and what kind of drugs were in the person’s system. Though the public and family members are anxious for answers, it’s important to remember the complexity of forensic toxicology tests and that accurate results take time.


  1. CNN Health. Why Don’t We Know Yet What Killed Prince?

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