How climate change could affect death investigations

In the first episode of CSI: Crime Scene Investigation, fictional entomologist Gil Grissom arrived at a crime scene and used tweezers to pull a maggot out of a dead body. Within moments, he announced that the age of the maggot indicated that the body had been dead for seven days.

The same approach applies in real life — entomologists use the larval stage of insects to detect time since death — though the science is more complicated and takes longer.

Real-world entomologists like Jens Amendt reference data from nearby weather stations to model the temperature of dead bodies, which will affect how quickly the insects grow.

But climate change is expected to make that analysis, which was already more nuanced than TV suggests, even trickier.

Weather has never been constant, but under climate change it is becoming more variable and extreme.

"We have two days of heat, of nice weather, and then thunder and storms and heavy rain," said Jens Amendt, a professor at the Institute of Forensic Medicine in Frankfurt am Main, Germany, describing recent weather where he lives. "That, I think, is an impact which we still don't understand."

Entomologists are beginning to model complex weather conditions, said Amendt, but research in the field is ongoing, and adds a new layer to their calculations. 

While the forensic scientists who spoke to CBC News didn't think climate change was having drastic effects on death investigations yet, they said the field will need to adapt as things get worse. 

Determining location of death

Another important aspect of death scene investigation is looking at the types of insects on the body. 

Finding insects that don't usually reside in the region where a body is found can signal that a body was moved from another location.

"Insects that you associate with an urban environment, for example, might be found on a body that's in the woods," said Tim Thompson, an anthropologist at Maynooth University in Ireland.

But as the climate changes and gets warmer, the normal ranges and migration patterns of many creatures are shifting. In the Northern Hemisphere, for example, insect species are showing up in areas further north that would have been too cold before. 

Forensic entomologists need to be aware that the insects at a body site may no longer match what's described in the published literature, said Thompson.  

Another possible issue is that extreme dry heat leads to faster natural mummification — the drying out of human tissue.

This makes bodies unappealing to insects like the blowfly which need "fresh and wet tissue," said Amendt.

The identity of the deceased

When police can't determine the identity of a body based on ID or other personal items, they sample DNA — but DNA databases are limited, which can leave investigators at a dead end.

The next step, said Lynne Bell, a professor of criminology at Simon Fraser University in Burnaby, B.C., can be to use a technique called isotopic geolocation to figure out where the deceased lived.

Bell, who researches this relatively new technique, uses unique water signatures to figure out where a body came from. The water that a person drank while alive influences the oxygen isotopes in their body, which can be linked to rain patterns in the area they lived.

"The signal we measure comes from drinking water and ultimately that comes from rainwater," she said. The baseline data for geolocation comes from measurements going back decades.

As rain patterns change due to climate change, she said, the data will eventually become out-of-date and inaccurate to current conditions — meaning that scientists will need to change their approach and wean themselves off of their go-to data.

"What's going to become stressful for some of us is the constant reevaluation of published research," said Bell. "Something's five years old or 10 years since it was published. Do we trust it anymore?"

Reinventing the wheel

Scientists don't know exactly how climate change will affect decomposing bodies, but they do know how to monitor for changes, said Bell. 

The issue is that academics share information by publishing, a process that can take an entire year.

"You might think you've just got a handle on what's happening in the region you live in, but … those conditions are going to keep changing," said Bell.

The impact of climate change will be different depending on where you are, said Bell.

This means that new research will have to be specific to each individual region's climate — a standard that current research has yet to meet.

"In terms of what's going on across all of Canada, in the North, in the middle, you'll be hard-pressed to get good data," said Bell.

The idea that climate change will influence forensic science is relatively new, said Thompson. 

He's been an assessor and accreditor of various forensic degrees in the U.K., and he has yet to see climate change appear in any curriculums. Still, in his time teaching, he said that sustainability issues are much more at the forefront of student's minds than in the past.

"The first thing is just to acknowledge that this is happening," he said.