Speaker 1: So back in the summer of 2011, investigators in Michigan
Speaker 1: were facing this just absolute geographical nightmare.
Speaker 2: Oh, the Baby Kate case.
Speaker 1: Right, yeah. This young child, who the media ended up
Speaker 1: calling Baby Kate, had tragically gone missing. And the suspect,
Speaker 1: her father, gave police this incredibly vague account of where
Speaker 1: he had been that day. So based on his timeline
Speaker 1: and his vehicle... the search grid ballooned to cover like
Speaker 1: seven different counties.
Speaker 2: Which is just a massive area.
Speaker 1: It's impossible. I mean, searching seven counties for a single
Speaker 1: hidden location is like looking for a needle in a haystack,
Speaker 1: if the haystack was the size of a mountain range.
Speaker 2: Right.
Speaker 1: But the investigators, they have the suspect's shoes.
Speaker 2: And those shoes were covered in a very fine, seemingly
Speaker 2: inconsequential layer of dirt and plant matter.
Speaker 1: Yeah, which is where a botanist named Matt Von Conrad
Speaker 1: stepped in. Because he didn't just look at the shoes
Speaker 1: and see mud. He put the debris under a microscope.
Speaker 1: and found a highly specific combination of moss fragments. And
Speaker 1: because moss is incredibly picky about its environment, requiring very
Speaker 1: specific levels of shade and moisture and soil acidity, that
Speaker 1: combination of microscopic plants served as essentially a GPS coordinate.
Speaker 2: It's amazing.
Speaker 1: It took a search grid of seven counties, this impossibly
Speaker 1: vast expanse of land, and shrank it down to a
Speaker 1: microhabitat measured in tens of square feet.
Speaker 2: Wow.
Speaker 1: So today we are diving into a stack of research
Speaker 1: and case files on something called forensic botany.
Speaker 2: Right.
Speaker 1: It's a practice of treating plants, twigs, seeds, pollen, and
Speaker 1: moss as physical evidence in criminal investigations. And our mission
Speaker 1: today is to explore how nature's quietest organisms keep a
Speaker 1: stubborn record of human actions. Yep. especially when human witnesses
Speaker 1: lie or disappear.
Speaker 2: It is a remarkable field, but we should probably establish
Speaker 2: a baseline right away.
Speaker 1: Sure.
Speaker 2: Plants are not magical oracles. We aren't talking about some
Speaker 2: mystical connection to the forest.
Speaker 1: Right, right.
Speaker 2: Plants are physical evidence, and they're governed by strict ecological rules.
Speaker 2: They have biological schedules. They are restricted to specific growing ranges,
Speaker 2: and they carry unique genetic fingerprints.
Speaker 1: Okay, let's unpack this, because it sounds almost like a superpower.
Speaker 1: But it is deeply grounded in biology. Exactly.
Speaker 2: When we look at a crime scene in a forest
Speaker 2: or a field, the expectation is that the crime is
Speaker 2: simply unwitnessed. But if you can read the ecology, you
Speaker 2: realize the environment itself is documenting the event.
Speaker 1: Before we get into the molecular genetics and the high-tech
Speaker 1: side of this, I want the listener to try something.
Speaker 1: Look down at your shoes right now. Or think about
Speaker 1: the jacket you wore the last time you went for
Speaker 1: a walk outside.
Speaker 2: Mm-hmm.
Speaker 1: What microscopic evidence are you unknowingly carrying with you? Because
Speaker 1: you are carrying something.
Speaker 2: You absolutely are. I mean, every single time you step outside,
Speaker 2: you are moving through the bulk of Earth's living biomass.
Speaker 2: You're brushing against pollen, picking up spores, crushing leaves, and
Speaker 2: transferring organic material from the landscape straight to your clothing,
Speaker 2: your hair, and your vehicle.
Speaker 1: It's everywhere.
Speaker 2: The environment is constantly rubbing off on you.
Speaker 1: I'm trying to visualize how we even got to the
Speaker 1: point where a court of law would accept this, though.
Speaker 1: You don't just walk into a courtroom with a microscopic
Speaker 1: piece of moss and point at a suspect.
Speaker 2: No.
Speaker 1: There has to be a foundation, like a precedent for
Speaker 1: treating nature as a witness.
Speaker 2: You need an incredibly strong precedent. And the foundation for
Speaker 2: forensic botany in the courtroom doesn't begin with a microscope
Speaker 2: and a leaf. It begins with a ladder.
Speaker 1: Oh, wow.
Speaker 2: Specifically in what was arguably the most famous criminal investigation
Speaker 2: in American history.
Speaker 1: Oh, the 1932 Lindbergh baby kidnapping.
Speaker 2: That's the one.
Speaker 1: This was the quote unquote trial of the century. I mean,
Speaker 1: Charles Lindbergh was an international hero for his solo transatlantic flight.
Speaker 2: Yeah.
Speaker 1: So when his 20 month old son was taken from
Speaker 1: his nursery in Hopewell, New Jersey, the entire country just
Speaker 1: came to a standstill.
Speaker 2: It was a massive deal.
Speaker 1: It was a tragedy that ended with the child found dead.
Speaker 1: But the kidnapper made a critical mistake. They left a
Speaker 1: homemade wooden ladder behind at the scene.
Speaker 2: And that homemade ladder became the most scrutinized piece of
Speaker 2: physical evidence in the world at that time. Wow. And
Speaker 2: that's where Arthur Kohler enters the picture. Kohler was a
Speaker 2: wood identification expert at the United States Forest Products Laboratory
Speaker 2: in Madison, Wisconsin.
Speaker 1: I have to pause on that because it's such an
Speaker 1: interesting historical detail. He wasn't a police scientist. No. He
Speaker 1: wasn't a detective.
Speaker 2: Not at all. Kohler spent his days answering industrial questions
Speaker 2: for lumber yards and builders. He studied wood grain, milling marks,
Speaker 2: and how different species of boards shrank and swelled based
Speaker 2: on ambient moisture. So when federal investigators brought him the
Speaker 2: Lindbergh Ladder, he approached it with a purely industrial anatomical methodology.
Speaker 1: So he just stripped away the context of the murder
Speaker 1: and looked at the biology of the wood.
Speaker 2: Exactly. He first identified the species used to construct the ladder,
Speaker 2: which were Douglas fir, ponderosa pine, and birch. Because softwoods
Speaker 2: and hardwoods have fundamentally different cellular structures, hardwoods like birch
Speaker 2: contain specialized cells called vessels for transporting water, which look
Speaker 2: like tiny pores under magnification.
Speaker 1: Oh, I see. Right?
Speaker 2: And softwoods like pine lack these vessels and rely on
Speaker 2: a different cell type called trachyids. So Kohler could easily
Speaker 2: prove the species.
Speaker 1: But knowing the latter was made of pine doesn't catch
Speaker 1: a kidnapper. Millions of things are made of pine.
Speaker 2: Right, exactly. Exactly. The breakthrough in the sources comes when
Speaker 2: he narrows his focus to one specific rail of the ladder.
Speaker 1: Okay.
Speaker 2: Because a piece of pine is not just a generic material.
Speaker 2: It grew in a specific place during specific weather conditions.
Speaker 1: Oh, right.
Speaker 2: Kohler studied the individual rail and noticed two crucial things. First,
Speaker 2: it had four very distinctive square nail holes.
Speaker 1: Okay.
Speaker 2: Second, the pattern of the annual winds, you know, the
Speaker 2: concentric circles you see when you cut a tree down.
Speaker 1: Yeah.
Speaker 2: That indicated that this specific rail hadn't just been milled
Speaker 2: directly from a log. The curvature and spacing of the
Speaker 2: ring showed that it had been sawn off from a
Speaker 2: much wider pre-existing board.
Speaker 1: I love the mechanics of this. So Kohler maps out
Speaker 1: the physical geometry of this wood. He tracks the milling
Speaker 1: marks to specific machines and specific lumber yards. And eventually,
Speaker 1: the investigation leads police to the Bronx apartment of a
Speaker 1: carpenter named Bruno Richard Hauptman.
Speaker 2: Right.
Speaker 1: They search his home. They go up into his attic
Speaker 1: and they find a floorboard with a large section missing.
Speaker 2: And this is where the analog methodology just reaches its peak.
Speaker 2: Kohler takes the ladder rail from the crime scene and
Speaker 2: the damaged floorboard from Hopman's attic and places them side
Speaker 2: by side.
Speaker 1: Wow.
Speaker 2: The pattern of the annual tree rings flowed perfectly from
Speaker 2: the attic board into the ladder rail.
Speaker 1: No way.
Speaker 2: Yeah. And furthermore, the four square nail holes in the
Speaker 2: ladder rail aligned exactly with the floor joists in the
Speaker 2: attic where the original board had been nailed down.
Speaker 1: So a piece of wood is essentially a jigsaw puzzle
Speaker 1: piece with a biological barcode printed on the side.
Speaker 2: That is a brilliant way to frame it. Tree wings
Speaker 2: are entirely dictated by the environment. A year with heavy
Speaker 2: rainfall produces a wide, thick ring because the tree grew rapidly.
Speaker 2: A drought year produces a narrow, dense ring. That sequence
Speaker 2: of wide and narrow bands becomes a permanent barcode of
Speaker 2: the weather that specific tree experienced.
Speaker 1: That's crazy.
Speaker 2: The wood in the attic and the wood at the
Speaker 2: crime scene shared the exact same barcode. They were undeniably
Speaker 2: once a single plank.
Speaker 1: But I'm imagining the defense attorneys at the time, this
Speaker 1: is 1935 when it goes to trial. Yeah. They must
Speaker 1: have fought violently to keep this guy off the stand.
Speaker 2: Oh, they fought tooth and nail. The defense argument was literally,
Speaker 2: and I quote, there is no animal known among men
Speaker 2: as an expert in wood.
Speaker 1: Wow.
Speaker 2: Yeah. They tried to frame him as a charlatan because
Speaker 2: forensic wood analysis simply wasn't a recognized legal concept. Right.
Speaker 1: It was totally new.
Speaker 2: But the judge recognized the empirical rigor of Kohler's work
Speaker 2: and allowed the testimony. By doing so, that judge permanently
Speaker 2: opened the courtroom door for dendrochronology, which is the study
Speaker 2: of tree rings and botanical anatomy.
Speaker 1: It's an incredible foundation. Just a man with a deep
Speaker 1: understanding of cellular structure, tracing the geometry of a tree.
Speaker 1: But we're talking about a massive piece of lumber here. Yeah.
Speaker 1: A ladder is macroscopic evidence. It makes sense that if
Speaker 1: you have a giant plank of wood, you can match
Speaker 1: the grain.
Speaker 2: Sure.
Speaker 1: My question is, how does this transition to the microscopic?
Speaker 1: What happens when the evidence isn't a ladder, but just
Speaker 1: a single leaf or a seed?
Speaker 2: Well, that requires a monumental leap in the science. We
Speaker 2: have to move away from visual anatomical matching and dive
Speaker 2: into molecular genetics.
Speaker 1: Okay.
Speaker 2: The case that pushed forensic botany into the genetic age
Speaker 2: happened recently. 60 years after the Lindbergh trial in a
Speaker 2: vastly different landscape.
Speaker 1: So we're looking at 1992 in Maricopa County, Arizona. A
Speaker 1: dirt bike rider is out in the desert west of
Speaker 1: Phoenix and discovers the body of a woman named Denise
Speaker 1: Johnson in a dry wash. It's a desolate area, but
Speaker 1: right near where she was found, there's a small cluster
Speaker 1: of Palo Verde trees.
Speaker 2: And Palo Verdes are incredibly common in the Sonoran Desert.
Speaker 2: They have this green bark that can photosynthesize And they
Speaker 2: drop these very distinct seed pods.
Speaker 1: Right. So investigators process the scene and they find a pager,
Speaker 1: which was a big deal in 1992. Oh, yeah. Huge.
Speaker 1: And that pager leads them to a suspect named Mark Bogan. Now,
Speaker 1: Bogan admits to police that he knew the victim. However,
Speaker 1: he is adamant that he was never at that specific
Speaker 1: desert dump site. He claims his truck never went anywhere
Speaker 1: near that wash.
Speaker 2: But the physical scene contradicted him. A detective named Charlie
Speaker 2: Norton noticed that one of the Palo Verde trees near
Speaker 2: the body, a tree they cataloged as PV-30, had a fresh,
Speaker 2: raw scrape on a lower branch.
Speaker 1: Okay.
Speaker 2: It looked exactly as if a vehicle had driven past
Speaker 2: in the brush and clipped the tree.
Speaker 1: And when police execute a search warrant on Bogan's pickup truck,
Speaker 1: they look in the truck bed and they find two
Speaker 1: Palo Verde seed pods. Right. Now, I'm putting myself in
Speaker 1: the shoes of a defense attorney here. Finding a seed
Speaker 1: pod from a tree that grows all over Arizona inside
Speaker 1: a pickup truck in Arizona doesn't seem like a smoking gun.
Speaker 1: It feels entirely circumstantial.
Speaker 2: And under normal circumstances, it would be. The defense would
Speaker 2: just say, you know, a pod fell on his truck
Speaker 2: while he was parked at the grocery store. To deep
Speaker 2: that defense, Detective Norton asked a question that no one
Speaker 2: had ever asked in a U.S. criminal court. He reached
Speaker 2: out to a plant geneticist at the University of Arizona
Speaker 2: named Timothy Hellant-Jarsis.
Speaker 1: Okay.
Speaker 2: And he asked, can you prove that these two specific
Speaker 2: pods in the truck came from that one specific scraped
Speaker 2: tree at the crime scene?
Speaker 1: Which is a wild request for 1992. I mean, human
Speaker 1: DNA profiling in courts was still relatively new and highly contested.
Speaker 1: Asking to profile a bush in the desert is a
Speaker 1: huge swing.
Speaker 2: It was a massive risk. Hellant-Jarsis decided to employ a
Speaker 2: technique that was cutting edge at the time called RAPD.
Speaker 2: That stands for randomly amplified polymorphic DNA.
Speaker 1: Okay. I think we need an ELI 5 here. Like,
Speaker 1: explain it like I'm 5 on RAPD. Because randomly amplified
Speaker 1: polymorphic DNA is a mouthful. How does this actually work?
Speaker 2: Fair enough. Imagine the DNA of a tree is an
Speaker 2: encyclopedia containing millions of sentences.
Speaker 1: Okay.
Speaker 2: Instead of trying to read the entire encyclopedia from start
Speaker 2: to finish, which would take years, RAPD acts like a
Speaker 2: search function that looks for a few very specific random sentences.
Speaker 1: Ah, I see.
Speaker 2: You take the DNA from the seed pod and you
Speaker 2: take the DNA from the crime scene tree. You apply
Speaker 2: chemicals that search for those random sentences.
Speaker 1: Right.
Speaker 2: If the pod and the tree both produce the exact
Speaker 2: same pattern of sentences and no other tree produces that pattern,
Speaker 2: you have a match.
Speaker 1: But how do you prove that in court? How do
Speaker 1: you prove that another tree down the street wouldn't just
Speaker 1: happen to have the same sentences? Ah. This is what
Speaker 1: stood out to me in the sources. The absolute rigor...
Speaker 1: of the scientific method the police applied to their own scientist.
Speaker 2: The blind test.
Speaker 1: Yeah.
Speaker 2: It is a beautiful piece of investigative work. To ensure
Speaker 2: Helen Joris wasn't just finding a generic Palo Verde profile,
Speaker 2: the police drove all around Phoenix. They went to Bogan's house,
Speaker 2: his workplace, his favorite bars, and they collected seed pods
Speaker 2: from 18 random Palo Verde trees.
Speaker 1: Wow.
Speaker 2: They sent all 18 samples to Helen Joris, but they
Speaker 2: also secretly slipped in extra unlabeled material from the crime
Speaker 2: scene tree PV30.
Speaker 1: Oh, that's smart.
Speaker 2: They essentially said, all right, prove it.
Speaker 1: And the results are phenomenal. Helen Jaras runs the RAPD analysis.
Speaker 1: None of the 18 random trees matched the pods found
Speaker 1: in the suspect's truck. Right. But the sample from the
Speaker 1: crime scene tree matched. And the secret blind sample the
Speaker 1: police slipped in also matched.
Speaker 2: If we connect this to the bigger picture, this case
Speaker 2: proved that an individual plant, not just a broad species,
Speaker 2: but a single living organism... can be a unique source
Speaker 2: of trace evidence.
Speaker 1: That's incredible.
Speaker 2: It established that plant genetics could withstand the exact same
Speaker 2: hostile cross-examination and rigorous courtroom standards that are applied to
Speaker 2: human DNA.
Speaker 1: But wait, I want to clarify a detail about the
Speaker 1: biology here, because the success of this case hinged on
Speaker 1: the background population.
Speaker 2: Yes.
Speaker 1: The sources mention that palaverdes in the wild are outbred.
Speaker 1: They rely on insects to cross-pollinate them, meaning every seed
Speaker 1: is a genetic mix of different parent trees.
Speaker 2: Mm-hmm.
Speaker 1: They are incredibly genetically noisy. What would happen if this
Speaker 1: crime took place in a suburban neighborhood next to a
Speaker 1: row of landscape trees?
Speaker 2: That is a critical limitation to understand. If a landscaper
Speaker 2: plants 20 identical cloned maple trees down a suburban street,
Speaker 2: they are all genetically identical. They are grown from cuttings
Speaker 2: of a single parent. So if a leaf from one
Speaker 2: of those maples falls into a suspect's car, DNA analysis
Speaker 2: cannot tell you which of the 20 trees it came from.
Speaker 1: Because they're clones.
Speaker 2: Exactly. The RAPD technique would show the exact same sentences
Speaker 2: for all of them. The match in Arizona was only
Speaker 2: powerful because the background population of wild desert trees was
Speaker 2: so diverse.
Speaker 1: Okay, that makes total sense.
Speaker 2: Forensic botanists have to constantly evaluate whether the flora at
Speaker 2: a scene is actually informative or practically useless. Right.
Speaker 1: If everyone in the room has the exact same fingerprint,
Speaker 1: dusting for prints doesn't help you.
Speaker 2: Exactly.
Speaker 1: So we've established that a single genetically unique tree... can
Speaker 1: tether a suspect to a specific location. But this assumes
Speaker 1: the police know where the crime scene is. What happens
Speaker 1: when investigators have a victim but absolutely no location? If
Speaker 1: the landscape is a mystery, how can plants help?
Speaker 2: To solve that problem, we have to shrink our scale
Speaker 2: even further. We move from the macroscopic ladder past the
Speaker 2: seed pod down to something that is biologically engineered to
Speaker 2: travel through the air. We are talking about pollen.
Speaker 1: I am fascinated by pollen. Because when I think of pollen,
Speaker 1: I just think of the yellow dust covering my windshield
Speaker 1: in the spring that makes me sneeze.
Speaker 2: Yeah, that's most people.
Speaker 1: But structurally, it is incredibly resilient.
Speaker 2: It is practically indestructible in the natural environment. The outer
Speaker 2: wall of a pollen grain is made of a polymer
Speaker 2: called sporopollinin. Sporopollinin?
Speaker 1: Yes.
Speaker 2: You can think of sporopollinin as microscopic Kevlar.
Speaker 1: Oh, wow.
Speaker 2: It is one of the most durable organic materials on Earth.
Speaker 2: It evolved to protect the fragile genetic material inside from
Speaker 2: UV radiation, drying out, and physical damage while the pollen
Speaker 2: travels on the wind or on the legs of an insect.
Speaker 1: And because it's so tough, it acts like a geographical ochre.
Speaker 1: I want to look at a deeply tragic case from
Speaker 1: June 2015 that perfectly illustrates this. A dog walker on
Speaker 1: Boston's Deer Island found a garbage bag containing the remains
Speaker 1: of a small girl. She became known in the media
Speaker 1: as Boston's Baby Doe.
Speaker 2: Right, I remember that.
Speaker 1: The police were at a total dead end. She had
Speaker 1: no usable fingerprints, generic clothing, and a nationwide composite image
Speaker 1: yielded no credible leads. But the investigators decided to look
Speaker 1: closer at the scene.
Speaker 2: They brought in analysts who essentially vacuumed the child's hair,
Speaker 2: her clothing, and a blanket she was found with, specifically
Speaker 2: targeting trace botanical evidence.
Speaker 1: I'm just picturing crime scene techs vacuuming a toddler's blanket.
Speaker 1: It sounds so delicate. But also, what are they actually
Speaker 1: hoping to find?
Speaker 2: Well.
Speaker 1: To the naked eye, they're just collecting dust. How does
Speaker 1: dust solve a murder?
Speaker 2: Because that dust isn't just dirt. It contains pollen grains
Speaker 2: that act as a botanical recipe of the environment the
Speaker 2: child had been in.
Speaker 1: A recipe.
Speaker 2: Forensic botanists call these recipes assemblages. When the analysts looked
Speaker 2: at the pollen from the child, they found a mix
Speaker 2: dominated by oak and pine.
Speaker 1: Which doesn't seem that helpful, right? I mean, oak and
Speaker 1: pine cover massive portions of the northeastern United States.
Speaker 2: True. But an assemblage is about the combination of elements.
Speaker 2: Alongside the common oak and pine, they found pollen from
Speaker 2: privet and cedar of Lebanon.
Speaker 1: Neither of which are wild native plants you'd find deep
Speaker 1: in a New England forest. Exactly.
Speaker 2: Privet is a common ornamental hedge. Cedar of Lebanon is
Speaker 2: an exotic tree often planted in landscaping.
Speaker 1: Oh, interesting.
Speaker 2: These are plants you find in residential suburbs, manicured parks,
Speaker 2: and domestic yards. Furthermore, the analysts found microscopic soot particles
Speaker 2: mixed in with the pollen.
Speaker 1: Soot?
Speaker 2: Yes, which strongly indicated an urban or highly trafficked environment.
Speaker 1: So instead of looking at thousands of square miles of
Speaker 1: rural forest or distant states, this microscopic cocktail of pollen
Speaker 1: and soot points investigators firmly toward an urban landscaped environment.
Speaker 2: It radically shrank the map. It told investigators where not
Speaker 2: to look, which saved thousands of hours of wasted effort.
Speaker 1: Wow.
Speaker 2: Within months, focusing on local urban areas, the child was
Speaker 2: identified as Bella Bond, a two-year-old from Dorchester, a residential
Speaker 2: Boston neighborhood.
Speaker 1: That's incredible.
Speaker 2: Pollen is rarely going to give you a specific street address,
Speaker 2: but it acts as an ecological constraint.
Speaker 1: And because that spore of pollen and armor is so tough,
Speaker 1: this ecological constraint can last for staggering amounts of time.
Speaker 2: Oh, absolutely.
Speaker 1: There is a case in the sources from Austria in 1959.
Speaker 1: Investigators were trying to locate a body, and they were
Speaker 1: examining mud caked on a suspect's boots. In that mud,
Speaker 1: they found fossilized hickory pollen.
Speaker 2: Fossilized pollen can be tens of millions of years old.
Speaker 2: When pollen settles into sediment, and that sediment eventually turns
Speaker 2: to stone, the spore pollen coat survives the geological pressure.
Speaker 1: Tens of millions of years. And because geology is so
Speaker 1: thoroughly mapped, Experts knew that there was only one very
Speaker 1: specific eroded rock outcrop in the entire region that contained
Speaker 1: that exact stratum of fossilized hickory pollen.
Speaker 2: Yes.
Speaker 1: The dirt on the boot was tied to a rock
Speaker 1: formation millions of years old. Police went to that exact outcrop,
Speaker 1: and that is where they found the body.
Speaker 2: It's a phenomenal demonstration of pollen as a constraint.
Speaker 1: Yeah.
Speaker 2: But we should also note that plants don't just stick
Speaker 2: to the outside of us. We consume them. And the
Speaker 2: durability of plant structures extends to forensic digestion analysis.
Speaker 1: Yes, the concept of the last meal. I was reading
Speaker 1: about Dr. Jane Bach, a prominent forensic botanist who pioneered
Speaker 1: a lot of this work. She analyzed the stomach contents
Speaker 1: of victims to help establish timelines. But I have a
Speaker 1: fundamental question about this. If human stomach acid can dissolve
Speaker 1: a thick piece of steak, why can't we still identify
Speaker 1: the herbs from a slice of pizza?
Speaker 2: It comes down to cellular architecture. Animal cells, like the
Speaker 2: cells in a steak, are essentially water balloons. They have
Speaker 2: a very thin, flexible lipid membrane that stomach acid and
Speaker 2: digestive enzymes break down very quickly. Plant cells, however, are
Speaker 2: built like brick walls. They have a rigid outer layer
Speaker 2: made of cellulose, which provides the plant with structural support.
Speaker 1: And humans can't digest cellulose. We don't have the enzymes
Speaker 1: for it. That's why celery is basically negative calories.
Speaker 2: Precisely. The structural integrity of the plant cells survives the
Speaker 2: chemical bath of the stomach. In one of her cases, Dr.
Speaker 2: Bach was able to identify fragments of oregano, grass, and
Speaker 2: other specific vegetation still visually recognizable in a victim's stomach.
Speaker 1: Wow.
Speaker 2: Because biologists understand the gastric emptying rate, you know, how
Speaker 2: long it takes for a stomach to push food into
Speaker 2: the intestines, identifying that oregano corroborated exactly when the victim
Speaker 2: had last eaten.
Speaker 1: Which locks in the timeline.
Speaker 2: That, in turn, locked in the timeline of the crime itself.
Speaker 1: Here's where it gets really interesting, though. We've talked about
Speaker 1: pollen shrinking the map to a general neighborhood or tying
Speaker 1: someone to a geological outcrop. But the sources highlight a
Speaker 1: case involving a British forensic ecologist named Patricia Wiltshire.
Speaker 2: Oh, Pollen Pat.
Speaker 1: Yeah, Pollen Pat, where she did something that sounds almost supernatural.
Speaker 1: She used pollen to find a hyperlocal location.
Speaker 2: Wiltshire is a legend in the field. She worked a
Speaker 2: case where she vacuumed the footwell and the pedals of
Speaker 2: a suspect's vehicle. She extracted the pollen assemblage, that cocktail
Speaker 2: of microscopic grains. But she didn't just say, this comes
Speaker 2: from a forest. She realized the assemblage was so uniquely
Speaker 2: diverse that it had to come from a very complex,
Speaker 2: specific landscape.
Speaker 1: And she literally goes out to the countryside, finds a
Speaker 1: long hedgerow bordering a field, and starts walking along it.
Speaker 2: She walked the edge of this field, continuously observing the
Speaker 2: visible flora. She was looking at the physical plants growing
Speaker 2: in front of her, comparing them mentally to the microscopic
Speaker 2: recipe she had pulled from the car.
Speaker 1: Wow.
Speaker 2: She walked until the physical plants aligned perfectly with the
Speaker 2: pollen data. Right at a specific spot along this massive hedge,
Speaker 2: the mix of vegetation was exactly right.
Speaker 1: She just stops and says, it's here. And the police
Speaker 1: confirmed that was the exact dump site.
Speaker 2: It proves that if the landscape is diverse enough, if
Speaker 2: you have a sudden shift from a wet ditch to
Speaker 2: a dry bank, With different weeds and shrubs occupying overlapping zones,
Speaker 2: the pollen signal isn't just a regional broadcast. It becomes
Speaker 2: a hyperlocal fingerprint.
Speaker 1: That is just astounding. So pollen and dirt can act
Speaker 1: as a map, telling us where an event took place.
Speaker 1: But nature is dynamic. It doesn't pause when a tragedy occurs.
Speaker 1: A forest keeps growing. So what happens when the mystery
Speaker 1: isn't where the crime happened, but when? If police find
Speaker 1: remains in the woods... How can plants tell us if
Speaker 1: they've been there for two years or 20 years?
Speaker 2: This brings us to the concept of postmortem intervals, or PMI,
Speaker 2: established through botanical clocks. When a body is deposited outdoors,
Speaker 2: it creates a disturbance. Soil is turned over, plants are crushed,
Speaker 2: and eventually the remains become part of the substrate. The
Speaker 2: surrounding flora reacts to that disturbance. Moss colonizes exposed surfaces.
Speaker 2: Roots seek out the moisture and nutrients associated with decomposition.
Speaker 1: And because we know how plants grow, we can measure
Speaker 1: that reaction.
Speaker 2: Exactly. The sources detail a fascinating case from Massachusetts. Investigators
Speaker 2: uncovered a clandestine grave. During the excavation, they found a
Speaker 2: tree root that had grown laterally through the soil and
Speaker 2: passed directly through the skeletal remains, weaving right through the bones.
Speaker 1: Oh, wow. A root is just searching for water, and
Speaker 1: it finds this nutrient-rich pocket in the soil.
Speaker 2: Yes. Botanists carefully extracted a cross-section of that specific root.
Speaker 2: Using dendrochronology, the same principle Arthur Kuhler used in the
Speaker 2: Lindbergh case, but applied to roots instead of trunks, they
Speaker 2: counted the annual growth wings. Right. The root contained 27 rings.
Speaker 1: Wait, so if the root growing through the skeleton is
Speaker 1: 27 years old, that means the skeleton had to be
Speaker 1: in the ground before the root got there.
Speaker 2: It establishes a hard minimum postmortem interval. The grave has
Speaker 2: to be at least 27 years old.
Speaker 1: That's crazy.
Speaker 2: It sets an absolute floor on the timeline, which instantly
Speaker 2: allows detectives to filter missing persons reports, discarding anyone who
Speaker 2: went missing in the last two decades.
Speaker 1: The sources mention another case in Italy that used multiple
Speaker 1: plant clocks simultaneously. Yes.
Speaker 2: Skeletal remains were found in a dense hedge. Botanists analyzed
Speaker 2: roots that had grown into the victim's shoes. One shoe
Speaker 2: had a root with three years of growth. The other
Speaker 2: had a root with six years of growth.
Speaker 1: Okay.
Speaker 2: But they also looked at an elder shrub that had
Speaker 2: grown entirely over the site. The area was subject to
Speaker 2: routine municipal hedge trimming. The botanists reasoned that the body
Speaker 2: would have been exposed if it had been there during
Speaker 2: the last major trimming cycle. By combining the root rings
Speaker 2: with the age of the overgrowth, they confidently bracketed the
Speaker 2: time of disposal between the late 1990s and 2006.
Speaker 1: It's as if the environment is slowly building a cage
Speaker 1: of time around the evidence. But we keep talking about grand,
Speaker 1: long-term processes like tree rings and massive roots.
Speaker 2: Sure.
Speaker 1: Can this work on a shorter timescale?
Speaker 2: Yeah.
Speaker 1: What about mundane plants, like weeds in a vacant lot?
Speaker 2: It absolutely works with mundane plants, often through the biology
Speaker 2: of trauma and regrowth. We can look at Patricia Wiltshire
Speaker 2: again and her work on the 2002 Soham murders in
Speaker 2: the UK.
Speaker 1: Okay.
Speaker 2: The bodies of two young girls, Holly Wells and Jessica Chapman,
Speaker 2: were tragically found in a ditch. That ditch was thickly
Speaker 2: overgrown with stinging nettles.
Speaker 1: So when the perpetrator entered the ditch to hide the bodies,
Speaker 1: they had to trample the nettles. Precisely.
Speaker 2: When a plant like a stinging metal is violently flattened,
Speaker 2: its main vertical stem is often damaged or bent flat,
Speaker 2: interrupting its normal upward growth. The plant undergoes a physiological response.
Speaker 2: It breaks its apical dominance, which is the tendency to
Speaker 2: grow straight up, and redirects its energy into pushing out
Speaker 2: new lateral side shoots from the nodes along the flattened stem,
Speaker 2: seeking sunlight.
Speaker 1: Oh, it's adapting to the trauma. Yes.
Speaker 2: Wiltshire examined the length and development of those new lateral
Speaker 2: side shoots on the trampled nettles under the bodies. Based
Speaker 2: on the temperature, the season, and the known growth rates
Speaker 2: of that specific weed, she calculated that the regrowth took
Speaker 2: roughly two weeks.
Speaker 1: Wow.
Speaker 2: That two-week botanical clock perfectly corroborated the timeline of the suspect,
Speaker 2: Ian Huntley, ultimately helping to secure his conviction.
Speaker 1: It is deeply impressive. But I imagine there are major
Speaker 1: caveats here. Nature isn't a digital stopwatch.
Speaker 2: It is not, and that is a crucial point for
Speaker 2: any forensic botanist testifying in court. Botanists provide minimums and ranges,
Speaker 2: not exact obituaries. Right. Think back to the root with
Speaker 2: 27 rings. That tells us the root is 27 years old,
Speaker 2: but it doesn't tell us how many years it took
Speaker 2: for the root to travel through the soil and reach
Speaker 2: the grave in the first place. Furthermore, if a tree
Speaker 2: experiences severe trauma or extreme drought, it might simply not
Speaker 2: produce a ring that year. A missing ring can throw
Speaker 2: off a timeline if an expert isn't careful.
Speaker 1: So the expert has to constantly qualify their findings, like,
Speaker 1: this grave is at least this old.
Speaker 2: Exactly. You are providing a biological bracket.
Speaker 1: We've covered a lot of ground here. We have Kohler's
Speaker 1: wood grain matching, Helen Jaris using RAPD DNA to match
Speaker 1: a seed pod, pollen acting as a geological anchor, and
Speaker 1: roots acting as clocks.
Speaker 2: Yeah, it's a lot.
Speaker 1: If these botanical tools are so staggeringly powerful, my question is,
Speaker 1: why isn't this standard protocol? Why isn't a botanist at
Speaker 1: every single crime scene?
Speaker 2: Because the reality of forensic botany is incredibly unglamorous. The
Speaker 2: science is sound, but the mechanics of the discipline, you know,
Speaker 2: how evidence is transferred, how it is collected, the brutal
Speaker 2: fights in the courtroom and the sheer scarcity of qualified
Speaker 2: experts create massive bottlenecks.
Speaker 1: Let's start with transfer. Because if I am a criminal
Speaker 1: and I know I just dragged something through a patch
Speaker 1: of stinging nettles, my first instinct is to go home,
Speaker 1: throw my clothes in the washing machine on hot, And
Speaker 1: pressure wash my truck.
Speaker 2: Right.
Speaker 1: Does this evidence really survive a determined cleanup?
Speaker 2: It survives far more often than criminals think because microscopic
Speaker 2: plant matter is tenacious. Transfer doesn't require a violent struggle. Okay.
Speaker 2: A seed pod falls into a truck bed simply because
Speaker 2: a branch hangs low over a dirt road. Pollen gets
Speaker 2: trapped deep in the fibers of a fleece jacket because
Speaker 2: fleece acts like a microscopic net.
Speaker 1: Oh, sure.
Speaker 2: You kneel down in a damp patch of soil and
Speaker 2: moss fragments wedge themselves into the stitching.
Speaker 1: Of your boots. And a washing machine doesn't get that out.
Speaker 2: A washing machine cleans the broad surfaces, but it rarely
Speaker 2: flushes out the deep seams of denim, the Velcro on
Speaker 2: a jacket, or the internal tread of a work boot.
Speaker 2: Botanists know exactly where to look for these hidden assemblages.
Speaker 2: They check the stair tire wells of vehicles, the air filters,
Speaker 2: the deeply embedded ridges of brake pedals. or even the
Speaker 2: roots of a suspect's hair long after a shower.
Speaker 1: That's crazy.
Speaker 2: To the naked eye, the suspect looks clean. Under a microscope,
Speaker 2: they are still covered in the landscape.
Speaker 1: But if it's that tenacious, the bottleneck must be at
Speaker 1: the crime scene itself. The detective is actually collecting the material.
Speaker 2: This is where cases are most frequently lost. The average
Speaker 2: crime scene investigator is trained to look for blood, ballistic casings,
Speaker 2: and fingerprints. They are not trained to look for a
Speaker 2: broken twig or a specific species of grass. Right. When
Speaker 2: botanical evidence is collected, it is often collected improperly. Plant
Speaker 2: matter sealed in airtight plastic bags will quickly rot and mold,
Speaker 2: destroying the DNA.
Speaker 1: Oh, man. I read a detail in the sources that
Speaker 1: made me wince. The absolute nightmare scenario for a botanist
Speaker 1: is a detective arriving at the lab and handing them
Speaker 1: a plastic bag labeled Leaves from the Woods.
Speaker 2: Oh, it is infuriating because it renders the evidence practically useless.
Speaker 2: Suppose a detective hands me a leaf found on a
Speaker 2: victim's body. If they don't bring me anything else, what
Speaker 2: am I comparing it to? Best practice in botanical collection
Speaker 2: is highly cinematic. You must photograph the plants in place
Speaker 2: before anything is moved. You collect from the body. But crucially...
Speaker 2: you must collect a systematic set of control samples from
Speaker 2: the surrounding environment.
Speaker 1: This goes right back to the Palo Verde tree in Arizona. Yeah.
Speaker 1: You have to establish the background population. Exactly.
Speaker 2: If you bag the leaves near the victim, you must
Speaker 2: also bag labeled control samples from 10 meters north, 10
Speaker 2: meters south, 20 meters away, and from the path leading
Speaker 2: to the scene. Yeah. If you don't know what is
Speaker 2: normal for that specific forest, you cannot prove that the
Speaker 2: leaf on the suspect's shoe is uniquely tied to the
Speaker 2: crime scene.
Speaker 1: Which brings up the risk of overclaiming. Whenever a scientific
Speaker 1: method yields amazing results, there is a temptation to treat
Speaker 1: it like magic.
Speaker 2: This raises an important question about the ethical duty of
Speaker 2: the expert. Every powerful method attracts overconfidence. Plant DNA was
Speaker 2: revolutionary in 1992, but the RAPD method Helen Jarrus used
Speaker 2: is no longer the gold standard. It could be finicky
Speaker 2: and hard to reproduce perfectly in different labs. Modern forensic
Speaker 2: genetics prefers more stable markers.
Speaker 1: The sources mention things like SNPs and microsatellites. Again, I
Speaker 1: need an ELI-5 on this. What is the difference between
Speaker 1: RAPD and SNP?
Speaker 2: Well, SNP stands for a single nucleotide polymorphism. If DNA
Speaker 2: is an instruction manual, a SNP is a single letter
Speaker 2: typo in a specific word. It is highly precise and
Speaker 2: easy to verify. Microsatellites are areas of the DNA where
Speaker 2: a short sequence of letters stutters and repeats over and
Speaker 2: over again. Counting the number of stutters is highly reproducible.
Speaker 1: Got it.
Speaker 2: Moving to these markers makes the science more robust, but
Speaker 2: it requires highly specialized labs.
Speaker 1: And even with robust science, botanists can disagree, right? Yeah.
Speaker 1: I'm thinking of the Casey Anthony trial in Florida.
Speaker 2: Oh, yes.
Speaker 1: That was a massive media circus, and forensic botany was
Speaker 1: right in the middle of it.
Speaker 2: It was a prime example of how messy this can get.
Speaker 2: You had a forensic botanist testifying for the defense, examining
Speaker 2: the root growth and leaf litter around where young Kaylee
Speaker 2: Anthony's remains were found.
Speaker 1: Mm-hmm.
Speaker 2: The defense expert used that botanical analysis to directly challenge
Speaker 2: the prosecution's timeline of when the body was placed there.
Speaker 1: And a jury of laypeople is sitting there listening to
Speaker 1: two scientists argue about leaf litter. How do they know
Speaker 1: who to believe?
Speaker 2: They often don't. Juries struggle to weigh dueling scientific interpretations,
Speaker 2: which is why the expert has a profound duty to
Speaker 2: remain objective.
Speaker 1: Right.
Speaker 2: You have a responsibility to be dull when the data
Speaker 2: is dull. If the roots only give you a minimum range,
Speaker 2: you emphasize the range. You don't tell a dramatic, definitive
Speaker 2: story if the biology doesn't support it.
Speaker 1: But perhaps the biggest hurdle isn't the science itself, but
Speaker 1: the lack of scientists. There just aren't that many people
Speaker 1: doing this.
Speaker 2: Professional forensic botanists are incredibly rare compared to the volume
Speaker 2: of outdoor crime scenes. It is almost always a side
Speaker 2: practice for a university professor or an ecological consultant. Because
Speaker 2: there isn't a botanist on every police payroll, plant evidence
Speaker 2: is missed far more often than it is utilized. simply
Speaker 2: because the reflex to look for it isn't ingrained in
Speaker 2: standard policing.
Speaker 1: So what does the future hold? If the bottleneck is
Speaker 1: the sheer difficulty of training detectives to spot this stuff,
Speaker 1: and the time it takes a human expert to analyze it,
Speaker 1: is technology going to bridge that gap?
Speaker 2: Technology is already bridging the gap, and the implications are staggering.
Speaker 2: We are currently seeing a massive shift toward environmental DNA,
Speaker 2: or eDNA, and a process called pollen metabarcoding.
Speaker 1: Metabarcoding, meaning instead of looking at one thing at a time,
Speaker 1: you're reading multiple barcodes simultaneously.
Speaker 2: Exactly. Historically, a palynologist, a pollen expert, would sit at
Speaker 2: a microscope for hours, manually counting and identifying individual microscopic
Speaker 2: pollen grains against a massive reference library.
Speaker 1: Sounds exhausting.
Speaker 2: It is exhausting specialized work. With metabarcoding, an analyst can
Speaker 2: take a single swab of dust vacuumed from a suspect's jacket...
Speaker 2: run it through a sequencer, and instantly read the genetic
Speaker 2: signatures of dozens of different plant species mixed in that dust.
Speaker 1: You just read the whole genetic soup all at once?
Speaker 2: Yes. It massively speeds up the initial phase of an investigation.
Speaker 2: Instead of weeks of microscopic analysis, a computer tells you
Speaker 2: within days that the dust on a victim's clothing contains
Speaker 2: urban privet, cedar, pine, and oak.
Speaker 1: That's incredible.
Speaker 2: But I must stress you still need the human expert.
Speaker 2: A computer can list the species. But a human botanist
Speaker 2: is required to interpret what that mixture actually means, whether
Speaker 2: it points to a rural forest or a landscaped suburban park.
Speaker 1: It is just an incredible evolution. We've gone from Arthur
Speaker 1: Kohler staring at square nail holes and wood grain under
Speaker 1: a magnifying glass in 1932 to Timothy Helen Jarris extracting
Speaker 1: DNA from a desert seed pod to the near future
Speaker 1: where a sequencer can map an entire microscopic ecosystem from
Speaker 1: a single swab of dust.
Speaker 2: The technological arc is breathtaking, but the underlying principle hasn't
Speaker 2: changed since 1932.
Speaker 1: Which brings us back to the core premise of why
Speaker 1: plants are such perfect detectives. They don't have an agenda. No.
Speaker 1: A tree does not recant its testimony. A patch of
Speaker 1: moss cannot be bribed or intimidated. A stinging nettle doesn't
Speaker 1: forget what season it was trampled. Exactly. Their memory is
Speaker 1: entirely physical and stubborn. A thick ring of wood from
Speaker 1: a rainy year, an indestructible spore of pollen and coat
Speaker 1: surviving for millions of years... or a bent stem putting
Speaker 1: out new shoots in the dark.
Speaker 2: They are not skeleton keys, of course. Forensic botany will
Speaker 2: not solve every murder. Right. The vast majority of cases
Speaker 2: are still and will continue to be solved by cell
Speaker 2: phone records, surveillance cameras, and human DNA.
Speaker 1: But they are the safety net. They are the threads
Speaker 1: that hold an investigation together when the human evidence rots
Speaker 1: away or lies or simply doesn't exist. In cold cases
Speaker 1: or in vast rural environments where there are no cameras.
Speaker 1: A microscopic seed pod or a few grains of pollen
Speaker 1: can completely shift the trajectory of a search. So think
Speaker 1: back to the question I asked at the very beginning
Speaker 1: of this deep dive. The next time you take a
Speaker 1: walk through a park or hike a trail in the woods,
Speaker 1: realize that you are participating in a constant invisible exchange.
Speaker 1: You are leaving a trace of yourself behind, and you
Speaker 1: are taking a microscopic piece of that landscape with you
Speaker 1: on your shoes and your clothes. So what does this
Speaker 1: all mean? It means the natural world is not just
Speaker 1: a passive backdrop. It is always watching. And it is
Speaker 1: always recording.
Speaker 2: And if we extrapolate that idea into the future, we
Speaker 2: arrive at a rather profound, perhaps even unsettling thought. We
Speaker 2: discussed the rapid advancement of environmental DNA and pollen metabarcoding.
Speaker 2: As this technology becomes cheaper and infinitely more sensitive to
Speaker 2: the point where we can read entire microscopic ecosystems from
Speaker 2: a casual swab of a doorknob or a shoe, we
Speaker 2: are entering a new era.
Speaker 1: Wow.
Speaker 2: We shed DNA everywhere we go and we pick up
Speaker 2: eDNA from everywhere we've been. If our physical environment is
Speaker 2: constantly silently mapping our exact movements through these biological assemblages,
Speaker 2: and if every room, every street corner, and every park
Speaker 2: develops a unique, instantly readable biological signature, does the concept
Speaker 2: of an unwitnessed space effectively cease to exist?
Speaker 1: Wow. If a machine can swab your shoe and tell
Speaker 1: you every plant you walk past today, that is both
Speaker 1: a miraculous tool for justice and an incredibly haunting reality.
Speaker 1: It really is. The woods are never truly empty. They
Speaker 1: are keeping the ledger. Well, that is all for our
Speaker 1: deep dive today. Thank you so much for joining us
Speaker 1: as we explore the silent witnesses in the woods. Keep
Speaker 1: your eyes on the trees and we will catch you
Speaker 1: on the next deep dive.