Yes, dead bodies can move on their own!

Yes!

A dead body can move after death during the decomposition process.

Post-mortem movement is of forensic relevance in death scene assessments.

Researchers observed significant movement in limbs like arms shifting position due to the breakdown of tissues and ligaments, even though ‘the movement is not voluntary or controlled by the nervous system’.

After death, the body breaks down into simpler organic matter through biological and chemical processes. This process can take anywhere from a few weeks to a few years, depending on a number of factors.

Experiment results support the conclusion that post-mortem movement does occur in all limbs of the body. The anatomical structure that produced the most movement was the right styloid process of the radius, moving a total distance of 51.65 cm. A surprising finding of the study was that most post-mortem movement occurs in the advanced decomposition stage, with the lower limbs being the most active. Post-mortem movement can be quantified using time-lapse imagery, with results supporting movement in all limbs, a process that was active for the entire study period. (1)

The movement occurred in all limbs after death, including in the advanced decomposition stages. In particular, they noted that the arms moved from being positioned down beside the body, to stretching out on either side. The movements relate to the process of decomposition, as the body mummifies and the ligaments dry out.

Human Bodies Move For More Than a Year After Death

An Australian scientist has shown evidence that human bodies move around significantly for more than a year after death, in findings that could have implications for detectives and pathologists around the world (2, 3).

Researchers studying the process of decomposition in a body after death from natural causes found that, without any external “assistance,” human remains can change their position. Bodies shift their positions as they decompose. They took photos of the decomposition process of the body over more than 17 months and found that the remains appeared to move on their own. For instance, while they initially placed the arms alongside the body, at one point, the researchers note, the arms shifted and were flung to one side.

Dead bodies can appear to move on their own due to the decomposition process, where gases build up inside the body from bacteria breaking down tissue, causing bloating and potential shifts in position, especially when combined with the contraction of ligaments and the activity of insects like maggots feeding on the decaying flesh.

The video added below is an age restricted video and is suited for only adults. Watch it only if you think you can handle the decomposition process without any fear or disgust. Only purpose of posting it is educating people about forensics.

Footnotes:

1.Quantifying human post-mortem movement resultant from decomposition...

2. Human bodies can move on their own after death, study finds

3. https://www.sciencedirect.com/science/article/pii/S2589871X19301421#!