Can Marijuana Be Detected in an Autopsy?

We take a look at the facts


If you’re a CSI buff, you’ve probably watched an episode or two thinking that any number of substances can be detected after someone has – ahem – kicked the bucket. It’s a logical stretch; after all, we’re living in a modern age.

However, the facts may just surprise you. Death brings about several changes to the human body (besides, you know, a person no longer being alive). This can include a variety of internal processes that can interfere with medical interpretations. Detecting substances like cannabis isn’t a straightforward scenario.

So, if you dread knowing that some last, epic toke sesh would be detected after you’ve bitten the proverbial bullet, you may just be in luck. We’ve gathered some of the latest research on just what can be found post-mortem, including whether cannabis can be detected.

What is an Autopsy?

Death, for lack of a better term, isn’t exactly cut and dried. An autopsy can’t begin until a person is declared deceased. This is typically done by an attending physician, an EMT, or a police medical examiner. Once this is done, then the autopsy process can begin.

The body is shipped to a facility where it can be examined. The autopsy process isn’t something for the faint of heart to read. So, we’ll keep it short and simple. Keep in mind that autopsies aren’t always ordered. When individuals have been battling chronic illnesses such as cancer or pass on due to old age, most of the time this isn’t a requirement.

During an autopsy, several things must occur:

  • A Post-Mortem Interval (PMI) is declared – experts must determine how long a person has been dead. They do this using a variety of methods, including rigor mortis, insect activity, and stage of decomposition.
  • A pathologist (under the supervision of a medical examiner) will then place the deceased under a surgical procedure to determine the cause of death. This will include the removal of organs and examination of skin and muscles, including bruising or trauma.
  • After the procedure is complete the organs are replaced, and the body is sewn up.

Testing for Cannabis

A toxicology report is often done, but this is when things can get a little tricky. According to a recent study of cannabinoids post-mortem, most toxicology reports do not include a request for cannabis screening. There are exceptions to this rule, including when there is the death of a driver. However, even when this is the case, a post-mortem THC test can’t determine an accurate intoxication level.

This is due to a few factors, including decomposition. When decomposition begins, the levels of THC rise. Therefore, experts can’t reliably justify THC intoxication as a cause or attribute of death or an accident that may lead to death. Another factor includes each person’s physiology. Each person, when living, has a specific ceiling for what impacts or affects their mental or physical state of being. This makes determining impairment levels especially difficult for medical examiners.

If there are legal or criminal issues involved, this can become contentious. As most examiners can’t reliably determine intoxication levels, it can be disingenuous to pinpoint THC as the main culprit in a given scenario.

Also, most experts don’t order a report on cannabis due to the consensus in the medical community that cannabis is not a substance that kills. The issue becomes even murkier when the distribution of cannabinoids comes into play. Cannabinoids in the body don’t always distribute across tissues in predictable ways.

Testing Post-Mortem

Even if such a test were ordered, many of them would take time, as there needs to be extensive analysis. A board-certified toxicologist, Alan Hall of Laramie, Wo., states that “Some of the tests take days, weeks, months,” and he goes on further to clarify that such tests rely on the experience of those doing the testing. Those who are not familiar with how cannabis can be read may miss many of the results.

Others echo these sentiments. A coroner out of Colorado, Dr. Leon Kelly says that when it comes to reading the THC results of a deceased individual, “That number on the page doesn’t mean anything.” If this is the case, then it may be much ado about – well, nothing. If there isn’t a standard way to test how much a person is impaired before death, then there can’t be a solid consensus on how to interpret the results and therefore what it all means.

One study that was done by a coroner also out of Colorado, Andrea Tully, supports the assertion that THC levels can’t be reliably used after death. She states that death alters how the substance acts in the body. The study supports the notion that THC results after death are unreliable. Tully states that when asked to determine if marijuana could be a contributing factor in a person’s death, “We couldn’t really answer that question.”

Tully and her team then proceeded to try to find if there was a good comparison between levels of THC in life and those who were no longer living. To better capture the full picture, Tully took blood from different types of patients, including soon after patients were deceased. This kind of blood, she states, is often in pristine form. This is due to there being fewer bacterium and other organisms that often grow wildly in the body after a person dies.

She goes on to say that, often, blood from an autopsy draw isn’t “clean.” It is mixed with many elements that can obfuscate or muddy how results can be accurately read. The blood from a person that is being autopsied is often not only mixed with bacteria and microbes, but also fat and oils. She compared samples of blood drawn right after death and samples drawn several hours later. What Tully came to find was that the longer the blood sample sat, the more degraded it became and the higher the level of THC.

Why Does the Level of THC Increase After Death?

What Tully’s team found was that levels of THC in fresh blood were a lot lower. Marijuana is “lipophilic.” This means that cannabinoids are often stuck to the fats that are in the body. This causes some unusual deviations from the norm. It can cause levels of THC to rise. THC metabolites are a different case.

A drug metabolite such as the THC byproduct is the result of the body breaking down THC and making it into an altogether different compound. THC is thus transformed into something that the body can handle. It is, for lack of a better term, “metabolized.”

Science has pinpointed exactly how and when a body can metabolize a substance like THC. The process is the same for everyone on the planet. These metabolites can linger in the body for a longer period than the original substance.

This makes it much easier to zero in on a user and their drug levels with a bit more certainty. Metabolites made from THC don’t vary as much over time and are, instead, water-soluble. Despite these findings, it is still unclear as to how much credence to give to results garnered after death.

When it comes to litigation, things get even trickier. In cases such as reckless or negligent driving, there may be other factors related to the outcome. Due to the uncertainty of testing, stating that cannabis is a factor can be a bit misleading. Studies such as Tully’s will be sure to give judges, jurors, and others in our legal system pause.

Final Thoughts on Testing for Marijuana Post-Mortem

Despite the depictions we see in pop culture, there isn’t a clear consensus on just what intoxication by THC means for everyone. There are many ways that death, and the process of it, can change how THC tests. As decomposition sets in, clear and concise readings become harder to obtain, and the build-up of THC in the tissues occurs at a much higher rate than when a person was alive.

This makes it extremely difficult to gauge if a person was intoxicated or was affected by THC in a significant way. Additionally, how THC affects living people differs from each individual to the next. What may be a high level for one person may be almost negligible for another.

Thus, no strict guidelines can be used for measuring THC post-mortem. Another obstacle is the purity of samples. The longer a sample sits, the more degraded it becomes. Higher THC levels are often a hallmark of samples that have sat for more than several hours after death. This is due to THC being a compound with an affinity for fat and oils.

It becomes attached to the fats lining the body and, as time goes by, the levels continue to rise. And while measuring the metabolites may offer a more accurate assessment, it still may not be enough to get a complete picture.

In the end, there’s no reliable way to test for THC post-mortem. Theories abound as to what constitutes a safe level after death but there’s no true way to discern if such a level contributed in a meaningful way to death or an accident. Add in the fact that few toxicology reports test for THC under any circumstances. In cases of expected death, such as a prolonged illness, autopsies aren’t always done.