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10 Days Later: Biologists Find a New Way to Determine Time of Death

Their method worked in pigs over a week after death, long after the body's gone cold.

You've seen the crime dramas: someone discovers a dead body, the circumstances of death unknown. The forensics team runs some tests to uncover the deceased's final moments—and pin down exactly when those moments were.

But establishing how much time has passed post-mortem isn't always easy. At the moment, the most precise method is to go by the temperature of the body, which cools after death. That only works, however, until it's reached ambient temperature, a process that only takes up to around 36 hours. Some time later, one technique is to look at the presence of insects on the corpse.

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"In between, there is no reliable method established," Peter Steinbacher, a biologist at the University of Salzburg, told me in an email.

He's part of a team proposing a new method that could give a reliable estimation of "post-mortem interval" (PMI) up to ten days after death. They're presenting their work today at the 2015 meeting of the Society for Experimental Biology and published a paper on their research in the International Journal of Legal Medicine.

Their method measures something different: how much muscle proteins have degraded. This focus was based partly on findings from meat science, where researchers were more interested in how the degradation of proteins might affect things like the tenderness of pork. But the process of degradation itself was of interest to the Salzburg researchers.

"We have found indications that these muscle proteins degraded always in the same fashion," explained Steinbacher. "If this would also be true for humans, then this would be a good molecular clock for the time since death."

They ran some tests in dead pigs, looking at how different proteins in the animals' hind legs had degraded every six hours over ten days. They found that this followed a regular timeline. So by checking how the muscle protein has degraded, you could figure out an approximate time of death.

Steinbacher said the method was cheap and simple, and also benefited from the fact that muscle is found in most body parts. Just in case you don't find them all.

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While the research so far was only in pigs (which were chosen as they're closer to humans than rodent models), the team is hopeful it will apply to humans and has started tests. "Our new and preliminary data on human samples also show that the same break down products are present in humans," said Steinbacher. "This is of course very promising!"

They're also looking into how factors such as temperature could affect the results (most bodies aren't found in lab conditions, I guess).

It'll take a fair bit of further research before you see the method cropping up in CSI, but the authors concluded their follow-up work is "thought to offer a major improvement in actual forensic case analysis in the future."

Watch: Still Life, Motherboard's 2014 documentary on life, death, and an unassuming Mexican dentist whose proprietary chemical formula rehydrates corpses for identification.