You Probably Didn't Expect The Body To Move After Death, But It Can

It's a morbid inquiry, but scientists are nonetheless interested in tracking the body's movement after death. Such knowledge can help forensic investigators in their reconstructions of crime scenes, and it can also help aid in non-criminal investigations, as well. Indeed, the human body is keen to move quite a bit after death, and the more time that a corpse is left on its own, the more it moves. In fact, some parts of the nervous system often continue to function after the rest of the body dies, and some brain cells even ramp up in their activity after death. Thus, death isn't quite as cut-and-dry as we're often led to believe, and physical movement after death is surprisingly common.

Morticians and forensic investigators have known that bodies move after death for centuries, but the topic was given a formal study in 2020 when a team of Australian scientists decided to observe a decomposing corpse over the course of a 16-month period. The study, published in the journal Forensic Science International, concludes that significant post-mortem movement occurs in all four limbs, and that the radius, located around the forearm, moves the most. Indeed, the limbs are the most susceptible to movement after death, and their activity can be shockingly exaggerated over the course of decomposition.

Most notable was the timeline of decomposition. After 16 months, the body under observation seemed to "plateau" in its movement once it reached an advanced stage of decomposition, meaning it all but ceased to move significantly once its skeleton approached mummification. The researchers used a timelapse video to track the subject's movement, and after enough time had passed, movement of its limbs virtually stopped. In other words, cadavers settle into place over time, proving that our final resting positions at the moment of death are far from final.

If you're investigating a death, it's essential to understand how a dead body can move over time. This is especially true when a cadaver has been left untouched for a long time. Of course, decomposition can cause skin to sink and organs to drop, but the movement of limbs isn't as obvious. In the case of murder victims, for example, this movement is critical to reconstruct, so forensic scientists have to draw on a wide range of techniques and fields, including anthropology, chemistry, and biology.

Muscles operate via electrochemical impulses that are communicated through the nervous system. Anyone who has ever prepared a fish knows how "nerve endings" can make a fish's tail continue to kick even after its head is removed. The same is true for the human nervous system, and science has even suggested that the sense of hearing may be the final sense we lose, lingering up until the very end. Our muscles are powered by electrochemical reactions provided by our nervous systems. When our nervous systems are starved of oxygen and effectively dead, these chemicals are often released unintentionally and trigger muscular reactions. The process is gradual, and observers may witness dead bodies clenching their fists or flexing their jaws.

But electrochemical remnants aren't the only reason why dead bodies move after death. There's also the influence of gases. After a person dies, the countless microbes in their body continue to live, and their biochemical processes produce an internal chemical composition that quickly builds up in the form of gas. The digestive system is soon ripe with volatile materials, and system-wide decomposition expels gases. As these gases escape, they can make mouths move, arms raise, and diaphragms expand. Dead bodies don't breathe, but death isn't as cold and still as we might believe.