by David Kim

When a 4-­month-­old girl known to the public only as “Baby Kate” vanished from a small Michigan town in 2011, detectives eventually found themselves staring not at a crime-­scene photograph or a cell-­tower map, but at a smear of dried mud on the bottom of a suspect’s shoe. Embedded in that mud were scraps of moss and other microscopic life. Those plant fragments, analyzed by bryologists (scientists who study mosses, liverworts, and hornworts) and other specialists, helped narrow the search for the child’s “peaceful place” from seven counties to a patch of wetland measured in square feet and were part of the evidence that supported a murder conviction.

For most people, that kind of plant evidence still sounds exotic, even speculative. However, a growing body of casework shows that bryophytes can help estimate postmortem intervals, connect suspects to obscure locations, and even distinguish suicide from homicide. A comprehensive 2025 review by Jenna Merkel and colleagues, Green Clues: Unveiling the Role of Bryophytes in Forensic Science, gathers scattered reports, personal communications, and case studies from nearly a century of investigations and reveals that these small plants are an underused but potentially powerful form of trace evidence. For those within the criminal justice system, that has consequences. Prosecutors are beginning to rely on the microscopic green debris that clings to clothing, vehicles, and bones. Criminal defense lawyers will increasingly have to decide when to challenge those findings, when to seek their own experts, and when plant evidence is simply one more circumstantial strand in a larger forensic web.

From Forensic Botany
to Bryophytes

Forensic botany (the use of plant science in legal investigations) is no longer a curiosity. It has matured into a recognized subfield that examines everything from whole leaves and seeds to pollen grains, spores, plant DNA, and chemical signatures. Merkel and colleagues describe forensic botany as a discipline that is now used in crime-­scene reconstruction, food and pharmaceutical fraud, illegal logging, and biosecurity.

Within that expanding field, bryophytes have received comparatively little attention. Their review set out to map what is actually known. The team combed the scientific literature, media reports, and the “grey” world of conference abstracts and personal communications within the bryology community. Even though they found relatively few formal publications, their findings show bryophytes already in use in homicide investigations, missing-­persons cases, suicide inquiries, postmortem interval (“PMI”) estimates, and a cemetery desecration scandal.

For criminal justice professionals, the message is twofold. First, bryophyte evidence is not speculative theory. It has been used in real investigations and introduced in real prosecutions over many decades. Second, the record is spotty and often informal, which means the underlying methods have not been stress-­tested in the way that DNA, fingerprints, or bloodstain pattern analysis have.

Why Moss Makes Such
Sticky Evidence

Bryophytes are among the most common plants on Earth. Mosses, liverworts, and hornworts carpet forest floors, cling to rocks and concrete, colonize tree trunks, and even grow directly on bones. They are small but structurally complex. Many species build shoots in regular increments; some produce annual “tiers” that record growth year by year. Several properties make bryophytes attractive as forensic trace evidence:

Ubiquity and specificity: Mosses occur almost everywhere, from city sidewalks to remote wetlands. But individual species often occupy specific microhabitats – certain soil types, moisture regimes, or pH ranges. A mixed fragment of mosses on a shoe can therefore point to a surprisingly narrow set of locations, as in the Baby Kate case.

Ease of attachment: Bryophyte shoots and fragments readily snag on fabric, footwear, hair, and vehicle undercarriages. Once dried, they can remain lodged in treads and seams for months or years, protected from sunlight and mechanical damage. Investigators in several cases recovered intact stems and leaves from clothing and shoes long after the suspected contact with a scene.

Resilience over time: Mosses tolerate desiccation and freezing; they can resume growth when conditions improve. Even when they die, their physical structures – and in some instances their DNA – can persist long enough to be examined microscopically or genetically. In one study cited by Merkel et al., researchers recovered identifiable bryophyte material and usable DNA from old footwear and herbarium material.

Built-­in clocks: For some species, the number of shoot segments, the layering of stems or the size of reproductive structures correlates with age. When those relationships are known from ecological studies, they can be used to estimate how long a plant has been growing on a substrate – whether that substrate is a rock, a tarp, or a human skull.

These attributes mean that bryophytes can function both as location markers and as biological clocks. But they also mean that the evidentiary value of any given fragment depends heavily on local ecology, the availability of reference material, and the expertise of the person doing the identification.

Counting Moss to Tell Time: Postmortem Interval Cases

The oldest case in the Merkel review dates to 1929 in Tyrol, Austria, where investigators found a decomposing human skeleton colonized by several moss species, including Funaria hygrometrica and Ceratodon purpureus. By comparing the growth and reproductive structures of the mosses with what was known about their development, they estimated how long the body had been exposed, providing a postmortem interval when other evidence had long disappeared.

Decades later, Scandinavian investigators used similar logic in Stockholm. In 2006, human remains partially covered by a tarp were discovered in the city. With no immediate leads and no clear sense of how long the body had been there, police turned to the moss growing on the body and the tarp. A bryologist identified three species – Hylocomium splendens, Dicranum scoparium, and a Brachythecium species – and then aged each moss separately. H. splendens was roughly eight to nine years old, D. scoparium five to six, and the Brachythecium about two years. From that botanical timeline, investigators concluded that the remains likely belonged to a man who had been missing for at least a decade.

A case from Perugia, Italy, shows both the promise and the current limitations of this approach. In 2010, remains of an elderly woman were discovered in a wooded area. Moss colonizing the skull was identified as Leptodictyum riparium. There were no published growth-­rate data for that species, so the team turned to Hypnum cupressiforme, a morphologically similar moss with better-­documented growth. By counting stem segments and comparing them to Hypnum’s known growth, they estimated the moss to be 20 to 30 months old and, with other evidence, matched the remains to an 80-­year-­old woman who had disappeared about 2.5 years earlier.

In Portugal, bryophytes helped connect a skeletonized body to a long-­missing man. Investigators examining remains in a natural area documented a suite of mosses – among them Ptychostomum capillare, Hypnum cupressiforme, and Campylopus species – interacting with the bones and surrounding shrub roots. By analyzing both decomposition and plant colonization, they concluded that roughly six years had passed: about three years for decomposition and skeletonization, followed by another three years of plant growth. That six-­year estimate fit the disappearance of a 61-­year-­old man reported missing from the region.

For the defense, these PMI cases illustrate both the power and fragility of bryophyte evidence. When growth rates have been studied, when colonization contexts are clear, and when mosses are well preserved, they can provide temporal ranges that line up with missing-­person reports. But species-­specific data are sparse, environmental conditions can accelerate or slow growth in ways that are hard to reconstruct, and in several cases, key details come from personal communications or conference abstracts rather than full, peer-­reviewed studies. All of that is fertile ground for questioning the precision of any claimed postmortem interval in court.

Linking People, Places,
and Remains

Bryophytes do more than tell time. In several cases, they have connected suspects to specific locations in ways that would be hard to explain as coincidence.

In 2001 in Finland, a man’s body was found about five kilometers from the cafe where he had last been seen meeting three former criminal associates. When those three men were arrested as suspects, investigators sampled moss fragments from their shoes and clothing as well as from the vehicle they had used. Three species – Brachythecium albicans, Calliergonella lindbergii, and Ceratodon purpureus – were identified in those samples and then collected as reference material from the crime scene. Genetic analysis of the moss fragments and the scene samples showed they matched. This was the first documented use of bryophyte DNA in a criminal proceeding and helped link all three suspects to the remote location where the body was recovered.

Another case, from Burr Oak Cemetery in Alsip, Illinois, involved desecration rather than homicide. In 2009, employees at the historic cemetery were accused of digging up buried remains and reselling grave plots. Investigators found moss fragments buried with piles of discarded human remains. A Field Museum team identified the moss as Fissidens taxifolius and examined its condition to estimate how long it had been buried (no more than about two years), contradicting claims that the remains had been disturbed long ago. The botanical evidence helped establish a timeline that supported criminal charges and ultimately contributed to successful prosecutions.

And then there is the Baby Kate case in Ludington, Michigan. One year after 4-­month-­old Katherine Phillips disappeared, her father, Sean Phillips, wrote that she had died in an accident and that he had put her to rest in a “peaceful place.” Investigators were unable to find her body. What they did have was dried mud on the bottom of Phillips’ shoe, loaded with moss fragments and other microscopic life. Those samples were sent to a team at the Field Museum, which identified six bryophyte species, including several Sphagnum mosses, Plagiomnium ciliare, Dicranum flagellare, and a Hypnum species most likely corresponding to Calliergonella lindbergii var. americana.

The combination of mosses, sedges, and trees implied a very particular wetland habitat: red pine, white cedar, specific sedge species, and Sphagnum moss all growing in close proximity. That ecological fingerprint, according to one of the botanists involved, was rare in the region. Volunteers and law-­enforcement officers conducted an exhaustive search with plant identification guides, ultimately identifying only two grids, “Green Road” and “Lemke Drain,” that contained the full suite of species.

Diatom (microscopic, single-­celled algae with silica cell walls) analysis of the sediment on the shoe provided an independent line of support. The diatom community pointed to a wetland with low pH and high nutrients, again directing investigators toward Lemke Drain and away from other candidate sites. As Ludington Police Chief Mark Barnett put it, “The location that would support all these elements is so rare and specific to the surrounding area that it is only a matter of time before the exact location is found.” He added, “Locations showing a high probability of containing all of these elements have been established and need to be searched to either confirm or eliminate whether Sean was there.”

Phillips was convicted of second-­degree murder. Although Katherine’s body was never recovered, the botanical and diatom evidence shrank the search radius from seven counties to roughly 50 square feet around Lemke Drain, according to Merkel and colleagues. A subsequent conversation between Detective J.B. Wells, a co-­author of the scientific article, and Phillips led the defendant to point to an area on a map centered on that same drain.

For the defense, cases like these raise familiar questions about trace evidence. How comprehensive was the reference sampling? How common are those plant communities in the wider region? Were the identifications blind to the investigators’ theories? How much of the story rests on ecological inference rather than direct measurement? The Merkel review acknowledges that, while these cases illustrate the potential of bryophytes, many details remain circumstantial and context-­dependent.

Moss, Suicide, and the Reconstruction of Final Steps

Two cases in the Merkel study demonstrate how moss can influence determinations of manner of death, crucial questions in any criminal investigation and often central to defense strategy.

In Taipei in 2005, an adult man was found hanging from a tree. Investigators needed to know whether they were dealing with suicide or homicide. They noticed green smears on the inside of the man’s wrists and moss growing on the tree branch from which he had been suspended. The species was not identified in the report, but the correspondence between the smears and the tree moss suggested that the man had acquired the moss while tying the rope himself. That supported a conclusion of suicide and ended further criminal investigation.

A more detailed example comes from Italy, where a young woman died after falling from a mall terrace. Without eyewitnesses or surveillance footage, investigators could not tell whether she had jumped or been pushed. During a careful survey of the stairwells, walkways and terrace, forensic teams found moss growing along the paths leading to the parapet. They also recovered fragments of Tortula muralis and Ptychostomum capillare from the soles of the woman’s shoes and from the parapet itself.

The same two species were found along the approach routes, on surfaces that appeared to have been walked on. The pattern suggested that the victim picked up moss on her shoes while walking to the terrace, then transferred some of it to the parapet as she climbed onto it. This transfer sequence, combined with the absence of signs of a struggle, strongly supported suicide over homicide. Without the moss comparison, investigators would not have been able to reconstruct that last path with the same degree of confidence.

Criminal defense lawyers must recognize both the value and the danger of such reconstructions. On one hand, when plant transfer patterns line up with other evidence, they can corroborate a non-­criminal explanation and prevent a death investigation from turning into a wrongful prosecution. On the other, in a close case, a persuasive narrative about “where the moss must have come from” can be over-­interpreted by a jury if its limitations are not carefully explained.

Limits, Caveats, and the View From the Defense Table

The Merkel review is explicit about the constraints of bryophyte evidence. Identifying tiny plant fragments to species often requires specialized training and high-­quality microscopes, resources that many crime labs and police agencies lack. Many investigators may not recognize bryophyte material at all, let alone treat it as evidence worth collecting and preserving.

Even when moss is collected, growth-­based PMI estimates are delicate. Growth rates vary with temperature, moisture, light, and season. Reliable growth-­rate data exist for only a small fraction of bryophyte species, and not all species produce structures that can be used as “annual rings.” That is why, in the Perugia case, the team had to rely on a different, better-­studied species as a surrogate for Leptodictyum riparium. Those kinds of ecological analogies may be reasonable, but they are also vulnerable points under cross-­examination.

Merkel and colleagues also underscore that in most of the documented cases, bryophyte evidence is corroborative rather than standalone. Moss age estimates are combined with skeletal analyses and missing-­persons data. Moss fragments linking a suspect to a location are interpreted alongside diatoms, seeds, soil, fibers, or traditional biological evidence. In the Baby Kate case, for example, diatom analysis and broader plant ecology were essential to narrowing down to Lemke Drain as a likely site.

Finally, bryophytes rarely act in isolation. They host diatoms and other microbiota; they co-­occur with lichens, seeds, insects, and mineral particles. The Merkel review points to cases where lichens growing on bones in Argentina, and diatom communities in moss have been used to suggest time since death or water involvement. But it emphasizes that these applications depend on solid ecological baselines and careful sampling.

Practitioners should also recognize that this evidence can be a shield as well as a sword. In the 2011 trial of Casey Anthony, for instance, a forensic botanist was retained by the defense to determine the time duration the remains had been present at the discovery location based on plant growth patterns. That expert’s testimony contradicted the prosecution’s proposed timeline, demonstrating that botanical expertise can be used affirmatively to challenge the prosecution’s narrative. For criminal defense lawyers, these caveats and opportunities translate into practical questions:

Was the bryophyte evidence recognized and collected promptly, or was it a late-­discovered trace with uncertain history?

Were proper collection protocols followed? If moss fragments were not photographed in situ or collected using sterile techniques, the physical integrity of the evidence is open to challenge.

Who identified the species, using what reference material, and with what level of training?

Are the growth-­rate data local and species-­specific or extrapolated from another climate, another substrate, or another species?

How many alternative locations in the region share the same plant community as the alleged crime scene, and were they ruled out systematically?

The Merkel review does not purport to answer those questions for every case. But it makes clear that bryophyte evidence, like any trace evidence, must be handled extremely carefully by those who know what they are doing if it is to withstand scrutiny in court.

Where the Field Is Headed

Merkel and her co-­authors end with a set of recommendations rather than a claim that moss has already earned a fixed place in the forensic canon. They call for:

broader awareness and training among law enforcement and forensic professionals so that bryophytes are recognized as potential evidence and collected correctly;

expansion and curation of digital herbaria and regional reference databases, such as the Consortium of Bryophyte Herbaria, to make comparisons between crime-­scene samples and known specimens faster and more reliable; and

integration of emerging molecular tools, including environmental DNA (“eDNA”), into plant evidence workflows to strengthen identifications and reduce dependence on a small number of experts.

They also urge more ecological research focused specifically on questions that matter in court: how growth rates change under different environmental regimes; how long bryophytes and their DNA persist on various substrates; and how often particular species combinations occur across a landscape. Interdisciplinary collaborations between bryologists, forensic scientists, and law enforcement are presented as essential to building that evidence base.

The conclusion is cautious but pointed. Bryophytes are “highly valuable yet potentially underutilized” in forensic science. Their ubiquity, resilience, and ease of attachment make them strong candidates to link suspects, victims, and scenes or to provide timelines when other biological markers have vanished. At the same time, their usefulness is constrained by uneven data, limited expertise, and the practical realities of crime-­scene work.

For the defense, that mix of promise and limitation should feel familiar. Bryophyte evidence is unlikely to replace DNA, fingerprints, or digital data in the near term. But as more investigators are trained to notice the green smears on a wrist, the moss in a boot tread, or the tiny plants on a skull, it will show up in more reports and more courtrooms. When it does, counsel who understand both the science and its weaknesses will be best positioned – whether to challenge the evidence as overextended, to insist on appropriate experts, or in some cases, to use those same “green clues” to exonerate their clients.  

Sources: Jenna Merkel et al., Green Clues: Unveiling the Role of Bryophytes in Forensic Science, 10 Forensic Scis. Rsch. owaf026 (2025); Forensic Botany: Principles and Applications to Criminal Casework (Heather Miller Coyle ed., 2d ed. 2024); People v. Phillips, No. 324890 (Mich. Ct. App. Apr. 10, 2018); Associated Press, Dad Sentenced in Michigan’s ‘Baby Kate’ Disappearance, CBS News (Dec. 9, 2016); Rob Alway, Court of Appeals Affirms Sean Phillips’ Second-­Degree Murder Conviction in Baby Kate Case, Ludington Daily News (Apr. 10, 2018); Rob Alway, Supreme Court Will Not Consider ‘Baby Kate’ Murderer’s Appeal, Mason Cnty. Press (Nov. 2, 2018); Press Release, Field Museum, Solving Mysteries with Moss: New Paper Examines the History of Using Tiny Plants as Evidence in Forensic Cases (Nov. 10, 2025); Field Museum, Solving Mysteries with Moss: The History of Using Tiny Plants as Forensic Evidence, Phys.org (Nov. 11, 2025).

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