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Blue Fly Witness: How 13th-Century China Cracked the Case with Forensic Entomology · Crime Night

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  Speaker 1: We're dropping you right into the scene. It's thirteenth century China.
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  Speaker 1: Think rural humid, the air thick with the smell of
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  Speaker 1: rice patties, damp earth. A peasant farmer has been found
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  Speaker 1: dead in his field and the wound is brutal, jagged,
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  Speaker 1: clearly made by a sickle, most common farm tool.
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  Speaker 2: Around, right, And that's the investigator's nightmare, isn't it. This
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  Speaker 2: isn't some neat contained crime scene. It's wide open, and
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  Speaker 2: the weapon, well, every farmer there owns one, an identical sickle.
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  Speaker 2: You've got suspect, sure, opportunity plenty, but actual human witnesses zero.
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  Speaker 2: So how do you possibly find the killer when the
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  Speaker 2: evidence itself seems to point everywhere and nowhere.
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  Speaker 1: You know, today that scenario screams cold case, years of work,
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  Speaker 1: DNA databases, complex forensics. But back then, centuries ago, the
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  Speaker 1: killer was identified fast. Yeah, justice wasn't delayed. And it's
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  Speaker 1: because the investigator understood how to read signs that others
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  Speaker 1: couldn't see, witnesses that were totally hidden right there in
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  Speaker 1: plain sight.
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  Speaker 2: It really speaks to this older understanding, maybe that the
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  Speaker 2: most reliable truth doesn't always from humans. When you're faced
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  Speaker 2: with a pile of identical tools, you can't just look
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  Speaker 2: at the metal. You have to go deeper, look at
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  Speaker 2: the biology. And often the most honest witnesses, well they've
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  Speaker 2: got six.
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  Speaker 1: Legs exactly because Tay, we're doing a deep dive into
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  Speaker 1: that precise science, the method that crack that thirteenth century
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  Speaker 1: case and honestly still provides crucial breakthroughs today. Forensic entomology.
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  Speaker 1: It's the world of insects, as these silent, impartial and
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  Speaker 1: just astonishingly accurate witnesses. Okay, so let's unpack that. Forensic entomology.
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  Speaker 1: It sounds complex, but what are we really talking.
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  Speaker 2: About here, Well, at its core, it's the study of arthropods,
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  Speaker 2: so insects mighte spiders, that kind of thing. As they
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  Speaker 2: relate to legal matters, especially death investigations, it basically treats
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  Speaker 2: these creatures not as pests, you know, things to swat away,
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  Speaker 2: but as data sources, really reliable sources that give us
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  Speaker 2: critical insights into say the conditions, the time, and sometimes
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  Speaker 2: crucially the specific location of a crime.
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  Speaker 1: Okay, time seems like the big one. The post mortem interval,
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  Speaker 1: the PMI. You hear about standard forensics body temp rigor mortis,
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  Speaker 1: giving these huge windows like five days, maybe two weeks,
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  Speaker 1: that's almost useless.
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  Speaker 2: In corere it often is. Yeah, and those indicators body temp, stiffness,
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  Speaker 2: they fade relatively quickly, they become less reliable. This is
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  Speaker 2: where the insects really shine ntomological evidence. It just cuts
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  Speaker 2: through that ambiguity. Instead of say a fourteen day guess,
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  Speaker 2: analyzing the insects, specifically their larvae and their development stage
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  Speaker 2: can narrow that time of death down sometimes to a
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  Speaker 2: precise forty eight maybe seventy two hour window.
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  Speaker 1: That kind of precision, Wow, that could literally make or
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  Speaker 1: break a case, determine guilt or innocence. But I mean,
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  Speaker 1: how solid is that? What about variables like a sudden
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  Speaker 1: cold snap or a heat wave. Doesn't that mess up
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  Speaker 1: the calculations.
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  Speaker 2: That's a really important point, and it's where the science
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  Speaker 2: gets quite detailed. We don't just guess based on averages.
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  Speaker 2: We use a concept called accumulated degree days or eighty
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  Speaker 2: D sometimes accumulated degree hours GDH. See insects, especially fly larvae,
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  Speaker 2: they're cold blooded. Their growth rate is almost entirely dictated
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  Speaker 2: by the temperature around them. We know for specific species
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  Speaker 2: the exact temperature thresholds and the time needed to get
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  Speaker 2: from one stage one in start to the next.
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  Speaker 1: So you're calculating the thermal energy needed for them to grow.
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  Speaker 2: Basically precisely, the forensic entomologist collects the largest, so the
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  Speaker 2: oldest larvae from the scene. They might even rear some
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  Speaker 2: in a lab under controlled conditions just to see the
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  Speaker 2: full cycle. Then crucially, they get the specific weather data
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  Speaker 2: for the crime scene location, our by our temperatures for
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  Speaker 2: that period, and they work backward calculating exactly how long
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  Speaker 2: it must have taken those larvae to reach the size
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  Speaker 2: they were when found. Given that specific weather, the local
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  Speaker 2: weather becomes the clock.
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  Speaker 1: That's yeah, that's incredibly detailed. Okay, let's switch gears to location.
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  Speaker 1: You said insects can tell us where something happened. So
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  Speaker 1: say a body is killed in I don't know, a
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  Speaker 1: damp forest, but then dumped miles away on some dry,
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  Speaker 1: open plane. How do the insects reveal that move? Right?
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  Speaker 2: This is what we call entomological mapping. It solved cases
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  Speaker 2: where you know, there's no confession, no witnesses to the dumping.
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  Speaker 2: Every single habitat a marsh, a desert, a specific forest type,
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  Speaker 2: high altitude, it has its own predictable community of insect species.
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  Speaker 2: They're unique to that place, endemic.
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  Speaker 1: So you're saying, if I happen to die in a
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  Speaker 1: particular spot, I'll attract the local insect population, the ones
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  Speaker 1: native only to that area.
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  Speaker 2: Exactly that. So if remains are discovered and they have
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  Speaker 2: insects on them or maybe pupa casings embedded that are
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  Speaker 2: completely wrong for the place they were found. Let's say
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  Speaker 2: desert beetles found on a body recovered from a swamp,
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  Speaker 2: that's basically undeniable proof the body was post mortem. The
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  Speaker 2: insects settled in one place, the original death site, and
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  Speaker 2: were then transported along with the remains. They become tiny
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  Speaker 2: living markers of the original location.
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  Speaker 1: Wow, Okay, so that pins down the wear. But let's
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  Speaker 1: get back to the timing the decay process itself. What
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  Speaker 1: actually happens biologically right at the moment of death that
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  Speaker 1: kind of flips the switch and calls in these specific insects.
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  Speaker 2: It's a remarkably fast ecologic shift. First, any insects that
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  Speaker 2: live on a living host, certain mites, maybe body lice,
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  Speaker 2: they leave almost immediately their environment, the living system is gone,
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  Speaker 2: and then almost instantly they're replaced. Four distinct functional groups
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  Speaker 2: of insects arrive, and they arrive in a fairly predictable sequence,
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  Speaker 2: a succession, all playing a role in decomposition.
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  Speaker 1: Okay, walk us through that succession. What are these four groups?
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  Speaker 1: What's each one doing?
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  Speaker 2: Think of it like a well, a biological disassembly line.
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  Speaker 2: Maybe The first group, the most noticeable usually are the necrophages,
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  Speaker 2: the direct feeders. This is where you get the huge
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  Speaker 2: numbers of blowflies, the Califoridae, and flesh flies, the coppagey
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  Speaker 2: day their larvae. The maggots consume the soft tissues. They
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  Speaker 2: do the bulk of the initial work.
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  Speaker 1: Primary cleanup crew got it pretty much.
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  Speaker 2: Then Group two arrives the predators and parasites. Now these
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  Speaker 2: insects aren't actually drawn to the body itself. They're drawn
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  Speaker 2: to group one. So you get things like rove beetles,
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  Speaker 2: steph Linnidae or hister beetles, very active predators feeding on
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  Speaker 2: the fly larvae. They kind of keep the first wave
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  Speaker 2: in check, right like.
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  Speaker 1: A natural checks and balances system happening right there exactly.
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  Speaker 2: Then Group three the omnivores. These are your generalists, think
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  Speaker 2: certain wasps, ants, some beetles. They'll feed on the body
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  Speaker 2: tissues and on the other insects already. They're the larvae,
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  Speaker 2: the predators, opportunists really and finally, Group four are the
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  Speaker 2: adventitious species. These guys don't feed on the remains at all.
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  Speaker 2: They just use the body as part of their environment,
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  Speaker 2: maybe shelter, maybe a place to hunt other smaller insects
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  Speaker 2: that are present spiders, centipedes, mites.
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  Speaker 1: Sometimes the whole process sounds incredibly complex, but it's that sequence, right,
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  Speaker 1: the timing of one group showing up after another, that's
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  Speaker 1: what build the forensic timeline.
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  Speaker 2: Absolutely, the presence of, say a specific predator from group
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  Speaker 2: two tells you that Group one flies must have been
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  Speaker 2: established for a certain amount of time. The later arrival
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  Speaker 2: of things like hyge beetles the Dermestidae, which specialize in
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  Speaker 2: dried skin and ligaments, signals a much later stage of
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  Speaker 2: decomposition biological clock stage by stage, And if you zoom
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  Speaker 2: out look at the bigger picture. The function is just
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  Speaker 2: fundamental biology or cycling, breaking down complex organic matter, returning
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  Speaker 2: nutrients to the ecosystem. The insects ensure everything gets cycled back,
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  Speaker 2: completing the loop that.
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  Speaker 1: Really grounds it. Doesn't it. It takes something that sounds
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  Speaker 1: gruesome and shows its essential ecological role. Okay, let's bring
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  Speaker 1: a full circle back to that origin story, the thirteenth
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  Speaker 1: century murder in China, the one documented in the Washing
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  Speaker 1: Way of Wrongs, the problem only the identical sickles. How
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  Speaker 1: did that investigator actually use this knowledge of insect attraction.
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  Speaker 2: It was brilliant, really in its simplicity, and it relied
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  Speaker 2: entirely on knowing which insect would be the most sensitive detector.
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  Speaker 2: The investigator had all the farmers bring their sickles. He
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  Speaker 2: laid them out side by side in the sun in
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  Speaker 2: the open field, and then they waited. They waited for
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  Speaker 2: nature's expert witness, the one they knew couldn't be fooled,
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  Speaker 2: the blue bottlefly al dabin Alasrak as it was known.
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  Speaker 1: The blue slide, and it was d only to the
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  Speaker 1: one sickle that still had microscopic invisible traces of blood
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  Speaker 1: tissue on it. It literally pointed out the murder weapons exactly.
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  Speaker 2: And that's the power of this particular group, the Califfer genus.
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  Speaker 2: They really are the stars of forensic entomology. What's just
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  Speaker 2: incredible is their sense of smell, their olfactory acuity, and
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  Speaker 2: their speed. We often talk about, you know, maybe a
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  Speaker 2: twenty four hour window for significant insect colonization. The blue fly,
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  Speaker 2: it's so sensitive it can locate and arrive at remains
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  Speaker 2: or even just minuscule traces of biological material within minutes
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  Speaker 2: of death or contamination minutes.
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  Speaker 1: That's and that efficiency, that near incallibility, that's what led
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  Speaker 1: to it becoming part of folklore.
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  Speaker 2: Yeah, precisely, that extreme sensitivity, that ability to find what
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  Speaker 2: humans can't see, is why that old saying emerged, The
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  Speaker 2: idea that if you committed a crime so perfectly concealed
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  Speaker 2: every trace you could boast, I'll make sure the blue
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  Speaker 2: fly won't even find your way. It meant you to
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  Speaker 2: achieve the impossible. Basically, because everyone knew that specific fly,
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  Speaker 2: it's almost impossible to fool if there's any biological trace left.
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  Speaker 2: It's nature's ultimate detection system.
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  Speaker 1: So, wrapping this up, what's the big takeaway for us today?
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  Speaker 1: We have this science rooted way back in the thirteenth century,
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  Speaker 1: still using these tiny organisms to bring incredible precision to
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  Speaker 1: modern crime solving, giving us answers on time, on location,
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  Speaker 1: when human memory confessions even sometimes our technology just falls short.
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  Speaker 2: And it really makes you wonder, doesn't it, thinking about
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  Speaker 2: the future. Given how incredibly sensitive these insects are, how
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  Speaker 2: quickly they can find and process microscopic biological traces, what
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  Speaker 2: else could they tell us? Could we, for example, analyze
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  Speaker 2: the chemical signatures within the insects, maybe in their digestive tracks.
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  Speaker 2: Could that lead us to finding traces of poisons or
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  Speaker 2: specific environmental toxins or drug metabolites that our current methods
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  Speaker 2: might miss entirely. It potentially opens up whole new avenues
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  Speaker 2: for investigation based on insect chemistry.
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  Speaker 1: That's a powerful thought to leave with. The body returns
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  Speaker 1: to the earth, but the story of its end might
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  Speaker 1: just be written in the life cycles of the smallest
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  Speaker 1: creatures attending its de Thank you for joining us on
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  Speaker 1: this deep dive into the world of these silent, six
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  Speaker 1: legged witnesses.