In 2009, a scandal was exposed at a cemetery just outside of Chicago. Workers at Burr Oak Cemetery in Alsip, Illinois, were accused of exhuming old graves, dumping the remains elsewhere on the cemetery grounds, and reselling the burial plots. When the case went to trial in 2015, one key piece of evidence was a tiny clump of moss. In a new study in the journal Forensic Sciences Research, researchers are sharing the first full scientific account of the case, detailing precisely how moss played a role in proving that a crime had taken place.
Matt von Konrat, the paper's lead author and the head of the botany collections at the Field Museum in Chicago, is a fan of detective shows on TV (the new paper is named after the BBC's Silent Witness), but he didn't imagine that his career studying moss would ever put him in the midst of a criminal investigation. "One day in 2009, I answered the phone, and it was the FBI, asking if I could help them identify some plants," says von Konrat. The FBI came to the Field Museum and presented von Konrat with a bit of moss that had been found eight inches below the soil, along with the re-buried human remains at the cemetery.
"The investigators wanted to know what kind of moss it was, and how long it had been buried in the soil," says von Konrat.
First, von Konrat and his colleagues examined the moss sample under a microscope and compared it with dried moss specimens in the museum's collections to determine that it was Fissidens taxifolius, also known as common pocket moss. "We did a survey of the different kinds of mosses growing near the crime scene, and that species of moss was not growing there," says von Konrat. "But when I surveyed the rest of the cemetery, we found a huge colony of that species of moss growing in the same area where the investigator suspected the bones had been dug up from. So that gave us pretty strong evidence that the remains had come from this other section of the cemetery."
But the investigators didn't just need the moss's species; they were also interested in its age. The case's defendants claimed that the bones must have been exhumed and reburied by someone else sometime before the defendants began working at the cemetery. Since the moss was buried along with the re-buried remains, knowing how long the moss had been underground would help prove the timeline when the bones had been reburied.
"Moss is a little bit freaky," says von Konrat. "Mosses have an interesting physiology, where even if they're dry and dead and preserved, they can still have an active metabolism, a few cells that are still active. The amount of metabolic activity deteriorates over time, and that can tell us how long ago a moss sample was collected."
A plant's metabolic activity can be estimated based on its chlorophyll — the green pigment used in photosynthesis. As plants decay and more and more of their cells cease to function, the chlorophyll in their cells degrades. The researchers measured the amount of light absorbed by the chlorophyll in moss specimens of known ages, including fresh specimens and ones that had been part of the museum's collections for 14 years. They then did the same test on the moss sample collected at the crime scene. The researchers determined that the evidence moss was only a year or two old —bolstering the case against the cemetery employees, who in 2015 were ultimately convicted of desecrating human remains.
"Every once in a while, a case comes along where the FBI has to call in experts to aid in the collection of evidence, do analyses, present the evidence to the prosecutors, and testify about their work if necessary to secure a conviction. The Burr Oak Cemetery case was one of those cases where we reached out to the Chicago Field Museum Botanical Program, which proved to be extremely invaluable because plant material inside the cemetery was key to charging four individuals and securing their convictions," says Doug Seccombe, a former FBI agent who worked on the case and was a co-author on the new paper.
Following the Burr Oak Cemetery case, von Konrat has been asked to consult on several other cases involving moss. But such instances are relatively rare in the world of forensic science: in 2025, he and several of his co-authors published another paper, delving into the use of mosses and other bryophyte plants as evidence in forensic cases. They found only a dozen-odd examples in the past hundred years.
"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 in society and around us," says von Konrat. "But most importantly, we want to highlight this microscopic group of plants as a tool for law enforcement. If we can elevate mosses as potential evidence, maybe it could help some families somewhere in the future."
