The vibrant maples, high-branching hickories and leafy beech that populate our forests absorb carbon from the atmosphere, and provide a habitat for the organisms that live there. But for forensic scientists, areas flourishing with such vegetation can be an added obstacle to locating dead bodies.
A number of researchers at the University of Tennessee have been working to change this. Their work, published in the journal Trends in Plant Science, makes a case for using plants, and specifically their biological behaviors, as a forensic tool to determine whether a decomposing human is nearby. They outline how compounds released from a dead body would stimulate a reaction in the plants that could change their appearance or composition. These changes, both visible and invisible to the naked eye, could be used as signals to a forensic team on an investigation, which would improve current challenges faced when searching for a missing person.
According to the National Institute of Justice, approximately 600,000 people go missing in the United States each year. Authorities find many of them alive and well, but they discover an estimated 4,400 unidentified bodies on an annual basis. A search for a missing body includes pedestrian surveys, aerial photography and dog teams, but searches that are in overgrown areas with rough terrain can be unsafe and challenging for forensic teams.
But researchers say a decomposing human body can release up to 50 times the amount of nitrogen in comparison to a dose of nitrogen fertilizer. This can cause a plant’s leaves to become greener and denser, as it ramps up the process of making chlorophyll. Healthy, nitrogen-fed plants also reflect more light, which can be measured with technology called a refractometer. Scientists say that for the purposes of remotely detecting these changes, a refractometer could be attached to drones. This remote technology could help teams use plants as guides to find bodies before they are not identifiable.
Previous research conducted on plant responses to human body metabolites other than nitrogen is scarce, but Neal Stewart, a plant scientist at University of Tennessee and co-author of the paper, is optimistic that his team will be able to fill in the gaps of this area, as outlined in their paper. Stewart has already started work on the university’s body farm, otherwise known as the anthropology research facility, to apply and further study how plants can be used in the forensic field.
“Plants have been overlooked in detecting dead people, but what people in agriculture know is that without plants there would be no life,” he says. “And so here we’re just using what nature gives us: the soil, the plants to find where there was life… it’s an interesting turn on agriculture and farming.”
Since June, Stewart has started identifying plant species that could potentially be used. Eventually, he and his team will fly drones with sensors over a forested area with a known decomposing body to track specific changes in plant appearances and composition over time. He hopes to compile concrete data that will provide a basic application that can be used to turn something in nature that was once a burden to forensic scientists into an asset.