In the first episode of CSI: Crime Scene Investigation, fictional entomologist Gil Grissom arrived at a crime scene and used tweezers to remove a worm from a dead body. He then announced that the age of the worm indicated that the body had been dead for seven days.
The same approach is used in everyday life – entomologists use the larval stage of insects to determine time since death – although the science is more complicated and time-consuming.
Entomologists like Jens Amendt use data from nearby weather stations to model the temperature of carcasses, which affects insect growth rates.
But climate change could make this analysis, which is already more nuanced than television suggests, even more difficult.
The weather has never been constant, but in the face of climate change it is becoming more so. more volatile and extreme.
“We have two days of heat, nice weather, and then thunder, storms and heavy rain,” said Jens Amendt, a professor at the Institute of Forensic Medicine in Frankfurt am Main, Germany, describing recent weather conditions where he lives. “I think it’s an influence that we still don’t understand.”
Entomologists are beginning to model complex weather conditions, Amendt said, but research in the field is currentand adds a new layer to its calculations.
While forensic experts who spoke to CBC News do not believe climate change will have a drastic impact on death investigations, they said the environment will have to adapt as the situation worsens.
Determining place of death
Another important aspect of examining a death scene is to look for the types of insects found on the body.
Finding insects that are not typically found in the area where a body was found may be a sign that the body was moved from another location.
“For example, insects that we associate with urban environments can be found on carcasses found in forests,” said Tim Thompson, an anthropologist at Maynooth University in Ireland.
But as the climate changes and it gets warmer, the normal ranges and migration patterns of many creatures are changing. For example, in the Northern Hemisphere, insect species are emerging in regions farther north that would previously have been too cold.
Forensic entomologists need to be aware that the insects found in a given body part may no longer match the descriptions in the published literature, Thompson said.
Another possible problem is that extremely dry heat leads to faster natural mummification – the drying out of human tissues.
This, Amendt says, makes insect bodies unattractive to insects like flies, which need “fresh, wet tissue.”
Identity of the deceased
When police can’t identify a body based on ID or other personal items, they take DNA samples – but DNA databases are limited, which can leave investigators in a dead end.
The next step could be to use a technique called isotope geolocation to pinpoint the deceased’s whereabouts, according to Lynne Bell, a professor of criminology at Simon Fraser University in Burnaby, British Columbia.
Bell, who is studying this relatively new technique, uses unique water signatures to figure out where a body came from. The water a person drank during life affects the oxygen isotopes in their body, which can be linked to rainfall patterns where they lived.
“The signal we measure comes from drinking water and ultimately rainwater,” she said. The underlying data for geolocation comes from measurements going back decades.
She added that as rainfall patterns change due to climate change, the data will become outdated and inaccurate over time for current conditions, meaning scientists will have to change their approach and abandon their existing data.
“What’s going to be stressful for some of us is the constant reassessment of published research,” Bell said. “Something is five or 10 years old. Do we still trust it?”
Reinventing the wheel
Scientists don’t know exactly how climate change will affect decomposing bodies, but they know how to monitor changes as they happen, Bell said.
The problem is that scientists share information through publication, a process that can take a whole year.
“You may think you have an idea of what’s happening in the region where you live, but … those conditions are going to change,” Bell said.
Bell said the effects of climate change will vary depending on where we are.
This means new studies will have to take into account the specifics of a given region’s climate – a standard that current studies have not yet met.
“If you consider what’s happening across Canada, in the north and in the centre, it’s going to be hard to get good data,” Bell said.
Thompson said the idea that climate change would affect forensics is relatively new.
He has assessed and accredited various forensic science courses in the UK and has yet to see climate change appear in any curriculum. Despite this, he said that sustainability issues are much more at the forefront of students’ minds during his time as a teacher than in the past.
“First of all, we just have to acknowledge that this is happening,” he said.
