Tiny plants, like moss, are easy to overlook. They're often as small as an eyelash, and they tend to grow on the ground in dark, wet places. But these small plants sometimes turn out to be big clues in forensic cases. A team of scientists learned that firsthand in 2013, when they were asked to use bits of moss to help pinpoint the location where a body was buried. Now, the researchers have published a paper in the journal Forensic Sciences Research, compiling all the cases they could find of mosses and their relatives being used to help solve crimes.
"With our paper, we wanted to highlight the significance of botanical evidence, because chances are, investigators are simply overlooking it because they don't know what they're looking at. We're hoping that our study helps show how important these tiny plants can be," says Matt von Konrat, Head of Botanical Collections at the Field Museum in Chicago and corresponding author of the paper.
Mosses are part of a family of plants called bryophytes. These are some of the most basic plants, and they don't have true stems, leaves, roots, or seeds. Their simple anatomy allows them to take in water and nutrients directly from their environment, which helps them thrive in shady, wet, boggy areas where more "advanced" plants often struggle.
Some bryophytes are extra-sensitive to their environment, with different species having particular affinities for different living conditions. "Because they're so small, they have all sorts of microhabitats— even if an area overall seems to be one sort of habitat, they can find a spot that works for them in the shade, or in the canopy, or even growing under the grasses," says von Konrat. "And different types of even smaller organisms can live on those mosses, which can give even further clues This means that mosses can be a valuable tool for forensic scientists looking to confirm details of where a crime took place.
In 2024, Jenna Merkel, then working on her Master's degree in forensic science at George Washington University, interned with von Konrat at the Field Museum. "I thought, why don't we look into writing a review of how bryophytes have been used in forensics?" says von Konrat. "So we reviewed 150 years of scientific literature to see how these plants have been used in investigations. Well, it turns out, the answer was, 'Not that much.'"
The earliest case the team found was from 1929, when the growth rate of mosses on a decomposing skeleton helped investigators determine how long ago the person had died. Over the past century, there have been at least ten more cases, in Finland, Sweden, Italy, China, and the United States, in which bryophytes have played a role in determining when, where, or how a criminal case had occurred.
The researchers' paper also serves as the first in-depth scientific record of a case von Konrat and several of his co-authors consulted on a decade ago.
In 2011, a baby girl named Kate was killed by her father, and her body could not be found. However, her father had given the police general information about where he'd buried her in northern Michigan, and his shoes had microscopic bits of plant material on them. In 2013, von Konrat led a team of botanists and volunteers in surveying the different grasses, trees, and mosses growing in the area, looking for a spot where the dozen plant species on the father's shoes could be found.
"There are hundreds of species of moss and dozens of species of grasses and trees living in that area," says von Konrat. "But based on the bits of moss, we knew what sort of micro-habitat we were looking for." The team ultimately identified a small area of about 50 square feet where Baby Kate was likely buried, narrowed down from the seven counties that law enforcement originally was investigating. Her father confirmed in a police interview that the spot pinpointed by the researchers is indeed where he buried his daughter.
The paper's authors hope that bryophytes can continue to help serve justice and bring closure to families affected by violence.
"Plants, and specifically bryophytes, represent an overlooked yet powerful source of forensic evidence that can help investigators link people, places, and events," says Merkel. "Through this paper, we aim to raise awareness of forensic botany and encourage law enforcement to recognize the value of even the smallest plant fragments during investigations."
