Murder will out but so, it seems, will science. The latest research is showing how trees could be a red flag for foul deeds
It’s not often that there’s good news in the world of murder, but developments in plant research say that minute changes in forest foliage – normally so good at disguising buried bodies – may actually signal where they are hidden.
Neal Stewart Jr., co-director of the Tennessee Plant Research Centre, said in Trends in Plant Science this month that the idea that trees could point the way for homicide detectives was not as farfetched as it might sound.
“In smaller, open landscapes foot patrols could be effective to find someone missing, but in more forested or treacherous parts of the world like the Amazon, that’s not going to be possible at all,” said Stewart Jr., a professor of plant sciences at the University of Tennessee.
“This led us to look into plants as indicators of human decomposition, which could lead to faster, and possibly safer body recovery.”
To further the research he teamed up with Dawnie Steadman, head of the Anthropological Research Facility, otherwise known as “the body farm”. A gruesome hectare of land near Knoxville, Tennessee, researchers take human cadavers donated to science, and position them around the ‘farm’ to study various forms of human decomposition.
Their findings have been invaluable to forensic crime investigators, but it seems that botany may take homicide detection in a new direction.
At the ‘body farm’ scientist have been assessing how “cadaver decomposition islands” — the zone immediately surrounding humans remains — change the nutrient concentrations of the soil.
They’re also looking at how these changes manifest in the nearby plants.
“The most obvious result of the islands would be a large release of nitrogen into the soil, especially in the summertime when decomposition is happening so fast,” Stewart was quoted as saying in Science Daily.
“Depending on how quickly the plants respond to the influx of nitrogen, it may cause changes in leaf colour and reflectance.”
While the obvious stumbling block is that trees could also identify any large forest-dwelling mammal, such as a dead deer or a dead bear, Stewart Jr. said there may be metabolites (the end product of metabolism) that are specific to humans.
He said that as humans typically have non-wild diets, there may be specific metabolites, like those from drugs or food preservatives, that have specific influences on plant appearance.
“One thought is if we had a specific person who went missing who was, let’s say, a heavy smoker, they could have a chemical profile that could trigger some sort of unique plant response making them easier to locate. Though at this stage this idea is still farfetched,” Stewart remarked.
Once the influences of cadaver metabolites on plants are better understood, search teams could develop imagers to scan plants for specific fluorescence or reflectance signals that indicate human remains are close by.
While some of this technology already exists, scientists still need to know which species of plant and the appropriate signals to look for.
“We’ve actually built a whole plant imager that can analyse fluorescence signatures,” says Stewart. “But the first steps are going to be very fine scale, looking at individual leaves and measuring how their reflectance or fluorescence changes over time when plants are near human remains.”
Once diagnostic spectra are compiled, researchers can send up drones that can analyse wide stretches of area in a short time.
“When you start to think about deploying drones to look for specific emissions, now we can think of the signals more like a check engine light – if we can quickly fly where someone may have gone missing and collect data over tens or even hundreds of square kilometres, then we’d know the best spots to send in a search team,” he said.