A clump of moss helped convict grave robbers at a Chicago-area cemetery

When the phone rang in Matt von Konrat's office at the Field Museum in Chicago one day in 2009, the caller was not a fellow botanist. It was the FBI.

Von Konrat, head of the museum's botany collections and a specialist in mosses and liverworts, was being asked to help with a criminal investigation. Workers at Burr Oak Cemetery in Alsip, Illinois, just outside Chicago, stood accused of exhuming old graves, dumping human remains elsewhere on the cemetery grounds, and reselling the burial plots. Among the evidence recovered from the scene: a small clump of moss, found eight inches below the soil alongside reburied bones.

A new paper in Forensic Sciences Research provides the first full scientific account of how that moss helped secure convictions in 2015. The case represents one of only a handful of documented instances where bryophytes -- the plant group that includes mosses, liverworts, and hornworts -- have served as forensic evidence.

Identifying the species, tracing the origin

The investigators needed two things from von Konrat: the identity of the moss and an estimate of how long it had been buried. The first question was answerable through standard botanical methods. Von Konrat and his colleagues examined the sample under a microscope and compared it against dried specimens in the Field Museum's collections, identifying it as Fissidens taxifolius, commonly known as pocket moss.

That identification opened a geographic line of evidence. When von Konrat surveyed the mosses growing near the reburial site, F. taxifolius was not present. But a large colony of the species was growing in a different section of the cemetery -- the same area investigators suspected the bones had originally been exhumed from. The moss had traveled with the remains.

Dating buried moss by its fading green

The second question was harder. The defense argued that someone else, prior to the defendants' employment at the cemetery, must have moved the remains. Establishing when the moss was buried would speak directly to that claim.

Mosses have an unusual physiology. Even when apparently dead and dried, some cells can retain metabolic activity. That activity fades over time, and it can be estimated through the moss's chlorophyll -- the green pigment that drives photosynthesis. As plant cells die, chlorophyll degrades, absorbing progressively less light.

The researchers measured chlorophyll light absorption in moss specimens of known ages, from fresh samples to herbarium specimens collected 14 years earlier. They then ran the same analysis on the crime scene moss. The result: the buried moss was only about one to two years old, placing its burial squarely within the period the defendants worked at the cemetery.

"Every once in a while, a case comes along where the FBI has to call in experts," said Doug Seccombe, a former FBI agent who worked on the case and co-authored the paper. The botanical evidence proved, in Seccombe's words, "extremely invaluable" in charging four individuals and securing their convictions for desecrating human remains.

An overlooked forensic tool

Forensic botany more broadly is a recognized discipline -- pollen analysis, wood identification, and algae studies all have established roles in criminal investigation. But mosses remain almost entirely absent from the forensic toolkit. In a 2025 survey paper, von Konrat and several co-authors found only about a dozen documented cases in the past hundred years where bryophytes had been used as evidence.

The reasons are partly practical. Mosses are small, often overlooked at crime scenes, and few forensic investigators are trained to recognize or collect them. But von Konrat argues the Burr Oak case demonstrates their potential. Mosses grow in specific microhabitats, making them useful for tracing geographic origins. Their slow chlorophyll degradation provides a biological clock. And because they are preserved in museum collections worldwide, reference material for identification is readily available.

"Mosses are often overlooked, and we hope that our research will help raise awareness that there are other plant groups out there, apart from flowering plants, and that these serve a very important role," von Konrat said. "Most importantly, we want to highlight this microscopic group of plants as a tool for law enforcement."

From BBC dramas to real courtrooms

Von Konrat, who named the new paper after the BBC series Silent Witness, has since been consulted on several other cases involving moss. The Burr Oak investigation, however, remains the most fully documented example of forensic bryology in a criminal prosecution.

The case also illustrates a broader principle in forensic science: the most useful evidence is not always the most obvious. DNA, fingerprints, and ballistics dominate crime lab work, but occasionally a case turns on something as humble as a few square centimeters of moss -- identified by a museum scientist who never expected the FBI to call.