TRANSKRYPCJA 🔗
WEBVTT
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Hi, I'm Wendy Zuckerman and you're listening to Gimlet Media's
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Science Versus. This is the show where we pit facts
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against fugitives. On today's show, forensic science. How much can
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you trust the science being presented in courtrooms? Forensic science
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uses scientific methods to investigate crime and prosecute people. We've
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all watched the telly. We know how this works.
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Pod just ran the formalin fixed tissue sample from Jane
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Doe 99 through GCMS.
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There's no traces of ecstasy, but he did find chloral hydrate.
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And if you need iced tea to translate for you.
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I hope you like hot wings.
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We're on the next plane to Buffalo.
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Forensic science has been used by law enforcement to catch
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and prosecute people for decades. Experts have gone into court
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testifying that they can match a strand of hair or
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a set of fingerprints to a suspect. And that testimony
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has been used to lock up countless bad guys. But
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what if they're not all bad guys? Recently, big questions
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have been raised about the credentials of forensic science. Questions like,
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is forensic science even a science? Sick burn, huh? Over
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the last few decades, the United States has freed more
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than 100 people whose convictions were partly based on forensic
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science evidence. And that's part of the reason why two
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of the most trusted science groups in the United States
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decided to take a critical look at forensic science. The
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National Academy of Sciences published their report in 2009 and
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the President's Council of Advisors on Science and Technology published
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their report earlier this year. Both of these reports questioned
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the validity of some forensic sciences and pointed out serious
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shortfalls in expert testimony. So, when it comes to solving crimes,
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there are lots of CSIs. The CSI New York, Miami,
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Las Vegas, Cyber... But then, there's science. There are a
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lot of areas of forensic science, from ballistics to drug
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testing to fibre analysis. But today, we're going to focus
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on the forensics that relate to the human body. These
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are some of the oldest forensic sciences, and they've been
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convincing juries of guilt or innocence for decades. First up,
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time of death. Using the best science available, how accurately
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can investigators tell when someone has died? Two, bite marks.
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Can you match a bite mark to a suspect's teeth? Three, fingerprints.
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How reliable are they? And four, hair. When a strand
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of hair is found at a crime scene, can you
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use a microscopic analysis to find out who left it there?
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A quick warning, today we're going to be talking about
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dead bodies and crime. So if you have kids with you,
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you might want to slip on some earbuds or save
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this episode for later. Let's start with time of death.
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One of the first things that forensic scientists are often
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called in to do at a crime scene is to
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figure out when someone died. You can check the body's
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temperature or how stiff it is or even do an autopsy.
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But if it's been more than four days, accurately predicting
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the time of death by just examining the body becomes
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a lot harder. For times like this, you need to
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call in a bug expert.
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Where is the bug man when you need him?
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They'll inspect the corpse for bugs that move in when
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the flesh has begun to rot. Sibyl Bouchelai is an
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associate professor of entomology at Sam Houston State University in Texas.
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Our producer Caitlin Sori and I visited her in her office.
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Her office door is covered with inspirational posters. If you
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took all of the veins from your body and laid
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them from end to end, you would die.
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When work feels overwhelming, remember that you're going to die.
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That's pretty nice. Science fact.
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Handy poster to have. Sybil is all about bugs. She
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researches them and since 2008, police have regularly called Sybil
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to check out the bugs at a crime scene. And
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she gets pretty excited about her work.
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Ah!
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I feel that all the time, though.
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What are we going to do now?
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Science!
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Sybil tells us that if you want to use bugs
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to tell how long a person has been dead for,
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you've got to figure out how old the insects that
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are crawling on the corpse are. Flies turn up on
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a dead body almost immediately. They'll start eating the body
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and then they'll really move in. They'll fall in love.
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They'll start making fly babies called maggots. And when the
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maggots grow up, they crawl off the body. They make
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a little shell for themselves like a cocoon. And then
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they'll escape out of their shell and fly away.
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For all the cases I ever do, what I'm looking
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for are the oldest maggot. And what that's going to
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tell me is how long... that body has had fly activity.
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Different species will colonise the body at different times. Blowflies,
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for example, like a fresh corpse, and they can colonise
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the body really quickly. Now, in the best case scenario
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for Sybil, the flies will get to make and fly
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babies right away. They'll lay their eggs and she will
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catch the first generation of maggots. From here, Sybil says
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that she can date the corpse with remarkable accuracy.
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I would look at age of the maggot, and then
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that would get you today.
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That would get you today?
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Wow.
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It can. It can get you today.
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A paper published this year looked at the accuracy of
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this technique. It modelled how different conditions, like places and seasons,
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can affect death estimations using bugs. In the best case,
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the paper found that reading the bugs on a body
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got it right to within one day. Change the conditions, though...
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And the estimations could be wrong by up to 19 days.
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When would that process not be as accurate as you'd
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like it to
be?
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If the death occurred in the winter and the remains
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were placed outside, there might not be a lot of
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insects around. And they wouldn't colonize the cadaver until temperatures
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warmed up enough.
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On top of that, there are always surprises. Like here's
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a weird one. There's some evidence that if the victim
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died with cocaine in their system, the maggots would eat
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that up and can be found talking someone's ear off
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at a dance party. No, they don't do that. They
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don't talk. Actually, when bodies have cocaine in them, there's
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some evidence to suggest that the maggots will grow up
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faster than they usually would, and this can affect the
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assessment of the time of death. Plus, in some cases,
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flies might get to an injured person before they're even dead.
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Don't think about that one while you're having breakfast. Sybil
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is still uncovering new things about which bugs turn up
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and when. She and her team are constantly doing experiments
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researching this, and she told us about one time when
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her team made a two-inch cut into the belly of
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a corpse. They then buried the body in a shallow grave.
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And then the team waited for the flies to show up.
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But this time, a very different bug got to the
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body first. Fire ants. They were taking dirt, putting it
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in the fluids of the wound, and then they would
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pick up the soggy piece of dirt and bring it
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back to the nest, possibly to slurp it up later.
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They were using the dirt as sponges, and they did
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this for nine days. And then on the ninth day,
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it rained, and it warmed up, and the body blew
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up like a volcano, just... All the guts came out.
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And at that point, the fire ants lost their monopoly
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of this small incision and the flies were able to
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come in and lay eggs. So that's an example where
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the fire ants could have interfered with the estimation by
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nine days.
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Wow.
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And that if you hadn't, if someone, so if someone
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just came into that dead body and just saw the
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maggots there.
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They would think, yeah. And they saw like eggs and
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itty bitty maggots. They would think that that body had
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been there for maximum time. An hour or two.
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Given all of these variables, the weather, the fire ants,
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the cocaine, researchers are still working out how often they
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get their estimations for the time of death using bugs wrong.
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Researchers from Texas A & M University wrote in a
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paper earlier this year that the accuracy of these estimates,
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generally speaking, are, quote, unknown, end quote. Sybil says that
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if your entire case rides on an entomologist, a bug expert,
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then your case is probably really bad. She says you
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need other types of evidence as well. Bugs are just
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one tool. Conclusion. Using flies to date a body has
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solid science behind it. We have a good idea of
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the life cycle of a fly and how quickly they
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grow once they've infested the body. But since each crime
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scene is different, you can't always rely on the bugs.
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Next up, bite marks. Bite marks have been allowed as
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evidence and routinely accepted in legal systems for decades. They've
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been used to investigate sexual assault and murder cases around
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the world, including in Australia, the UK, Norway and the US.
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Perhaps the most well-known case was of a serial killer,
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Ted Bundy. Two bite marks found on one of his
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victims were linked to Ted and this dental evidence helped
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secure his conviction. But bite marks had a really unusual
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entry into US courts. The first ever recorded victim in
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a bite mark legal case wasn't a person. It was
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a piece of cheese. Cheese?
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Yeah.
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Yep.
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Jeez.
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We heard this story from Chris Fabricant, who works at
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the Innocence
Project. This is a group of lawyers who
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work to overturn convictions. They've recently been working with the
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FBI and Department of Justice to look into cases where
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faulty forensic science has been used. So, back to the cheese.
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Chris told us that the scene of the crime was
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a grocery store in a small Texas town in the 1950s.
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A burglar had taken a bite of a piece of
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cheese and some enterprising young detective had found this piece
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of cheese and deduced that if we could find the
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person who bit this cheese, we have our burglar.
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The sheriff suspected a local drunk of robbing the store,
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so he gave him another piece of cheese to bite into.
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The detective then made a cast of that cheese as
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well as the one from the store. He compared them
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and said, boom, they're a match. The police department brought
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in a dentist who agreed with the cop. What a
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gooder day at work.
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They matched that cheese to the suspected burglar and we
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had bite mark evidence.
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Tasty or brie?
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You know, the truth is, I don't know what kind
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of cheese it was.
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Can you brieve him?
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Nah.
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OK, that was back in the 1950s. Bite mark cases
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eventually moved from matching marks on cheese to skin and
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they're still used in courts today. So here's how bite
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marks work today. Forget about the cheese. Say you have
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a body that's got what looks like bite marks. A
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photograph is taken of the patch of skin with the
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mark and if there's a suspect, a mould is made
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of that person's teeth. A dentist then takes this mould
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and uses it to bite something, like pig skin or
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even a cadaver, a dead body. She then takes the
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photograph of this second mark and then she puts the
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two photos side by side, one from the crime scene
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and one from the suspect's teeth. She compares how similar
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the bite marks are. And if they look very similar,
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then boom, it's a match. And your suspect did the biting.
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To see how this all happens in real life, we
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spoke to Barry Fisher, a forensic scientist who headed up
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the LA County Crime Lab, one of the biggest crime
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labs in America. By the way, crime labs are often
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part of police departments and it's where cops send their
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evidence to be processed by forensic scientists. Barry is now retired,
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but he remembers when he first arrived in L.A. all
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those years ago.
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The twinkling lights on the palm trees, it was at
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night when I got in, were magical a la Disneyland.
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I said, boy, this is wonderful. This is the place
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to be.
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Barry stayed in L.A. and ended up heading up the
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crime lab for 22 years. He's now retired. When he
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was head of the crime lab, he represented the squad
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as the president of the American Academy of Forensic Sciences.
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The thing is, even Baza has some concerns about bite
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mark evidence. For one, he told us that if you
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bite into skin, it bounces back. It can be stretched
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and contorted.
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The problem with skin is it's elastic, and it's a
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representation of the bite, but it's not going to be
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an exact representation.
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Of Another problem is that you can't reliably tell people's
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teeth apart. In 2010, a study looked at hundreds of
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sets of teeth and found, quote, uniqueness cannot be demonstrated,
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end quote. In a follow-up study using more than 1,000
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3D-scanned sets of teeth, it found again that teeth don't
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vary that widely from person to person. And there's one
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more thing you should know.
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There have been instances that have been reported where Some
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experts have claimed it to be a bite mark and
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others have said, no, it's not a bite mark, it's
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a scratch.
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Yep, a scratch. Earlier this year, that report by the
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President's Council of Advisors on Science and Technology wrote on
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the topic of bite marks that examiners, quote, cannot even
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consistently agree on whether an injury is a human bite mark,
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end quote. And so in April this year, after a
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six-month investigation, the Texas Forensic Science Commission unanimously recommended a
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moratorium on the use of bite mark analysis until the
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science improved. But the thing is, the President's Council report,
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the one we mentioned at the beginning of the show,
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wrote in September this year that bite mark analysis was
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so bad that it may not be, quote, salvageable, end quote.
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And.
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Yikes. And yet, despite the overwhelming scientific consensus that bite
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mark analysis is unreliable, some dentists, rebranding themselves as forensic dentists,
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have been going into court saying that they are certain
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that teeth marks found on a body belong to a suspect.
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Right now, Chris over at the Innocence Project has clients
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who are on death row because of cases that included
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bite mark evidence. Halfway through our conversation, he got a
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call from a colleague about a case he's working on.
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Well, we're on the side of science. I guess the
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judge is not going to want to hear from me.
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All right, we'll talk. No problem. We'll talk to you soon.
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What was that about?
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It's a death penalty case in Pennsylvania.
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Yeah.
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Where the prosecution is seeking to introduce bite mark comparison
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evidence and we are seeking to challenge the admissibility of
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that evidence.
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It's not clear how often bite mark evidence is introduced
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into court these days. No one keeps reliable records on this.
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But for Chris, these cases just keep popping up.
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Sometimes it feels like whack-a-mole, you know what I mean?
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And sometimes it just feels like moles with no whacking.
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Yeah.
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It's a process, never-ending process. It would be funny if
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there wasn't an innocent man on death row.
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Conclusion. Saying in court that you can definitively link a
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bite mark to an individual is bad science. Teeth aren't
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that unique and neither are the bite marks they leave
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behind on stretchy skin. After the break, getting fingerprints from
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a bloody crime scene and a big FBI bungle. Hey,
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it's Wendy from Science Versus, and I want to tell
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you about a podcast that I love, Science Friday. They
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cover all sorts of amazing things in the weird and
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wonderful world of science, from how concussions affect our brain
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to the inner secrets of a snake with a spider
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on its Welcome back. It's time to talk about fingerprints.
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Fingerprint analysis has been used for more than a century
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by investigators at crime scenes and prosecutors in court. and
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it's been used in some pretty amazing cases. Our forensic
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scientist Barry told us about one of his first cases
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involving fingerprints. It was from the 1980s. A woman was
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found dead in East LA. She'd been stabbed, and on
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her stomach, something was written.
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Written with some creamy substance. It's spelled out F-U-C, and
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then he ran out of room. It was pretty obvious
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what the perpetrator was trying to dispel out.
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Barry found a squeezed-out tube of moisturising cream in the
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woman's handbag, so his job was to try to get
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a fingerprint off that tube. But the tube was all
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crumpled up, so it was tough to get clean prints
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off it. It was then that he came up with
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a very clever plan. Barry used to carry around this
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handy toolbox with all sorts of gadgets, including a syringe.
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So he put the cap on the tube and closed
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it tight.
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Then I stuck the syringe into the bottom of the
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tube and I pulled out the plunger and I blew
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it up and just puffed right out.
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It worked. The team was able to get some pretty
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clean prints off this very crummy tube.
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It just kind of surprised me that how such a simple,
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obvious thing just Did the trick.
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Barry says the fingerprint on the tube was a match
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for the woman's boyfriend. And as Barry tells it, when
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the boyfriend was confronted with the prints, he confessed to
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the crime. But the question for us is how do
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forensic scientists know it's a match? On TV, they show
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fingerprints running up against a database until you hear that
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satisfying chirp followed by a... Russell Huntley's prints are on
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the Jupiters.
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That's not surprising.
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And if you need iced tea to translate for you...
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First spit.
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That lollipop out before I smack it out your mouth.
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But the science... is just a tad more complicated. Fingerprint
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matching technology doesn't match up an entire fingerprint swirl for swirl. Instead,
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they match up certain features on the fingerprint, like the
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point where the ridges end or split off. And there's
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no consensus on how many features need to be the
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same to call two fingerprints a match. Some countries say
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you need at least 12 points, some say 7 or 16.
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Still other countries, like the US, don't have any minimum
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number at all. This is ultimately because experts don't actually
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know how unique any of these points on a fingerprint are.
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Large population studies on the uniqueness of various features on fingerprints...
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haven't been done. Plus, on the TV, these points of
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similarity are all matched on computers. But like most dreams
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of technology, where's my jetpack? The technology just isn't that good.
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At the FBI, one of the best forensic crime labs
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in the world, there is a database of millions of fingerprints.
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But it only gets you so far. Here's Barry.
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We haven't gotten to the point where we're relying on
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computers to say it's an identification. What we're still using
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is
a human being to have a look at this stuff.
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So a computer will throw up potential matches. The FBI
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told us it's typically three. And then it's up to
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humans to narrow down those matches to an individual. And
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as Stalin once said, once you've got people, you've got problems. Well,
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it sounds like something he would say. Which brings us
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to this guy.
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My name is Dr.
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ETL.
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And you pronounce ETL like the letters ETL.
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You know the movie ET? So it's an L.
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ETL.
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Yes, perfect.
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00:21:47.119 --> 00:21:48.759
And you can say it a bit faster if you
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practice it a lot and say ETL. Thank you.
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Dr.
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ETL Draw at the University College London researches cognitive bias
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in experts. Or as he puts it.
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When smart people do stupid things, when do competent experts
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make mistakes, not because they're not motivated or drunk or whatever.
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So ETL says that all humans, dumb, smart, drunk, sober,
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have biases. And this can become a problem when analysing fingerprints.
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When it's not easy call, it's not clearly a match
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or not a match, then there's more interpretation involved. Subjectivity
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is involved. It's not totally objective. It's not CSI Hollywood.
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Now, these issues with fingerprints weren't really considered to be
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a problem until this happened. There's been a devastating terrorist
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attack in Spain.
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Without warning, a coordinated.
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Series of rush hour explosions struck three train stations in Madrid.
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In March 2004, bombs were detonated on several trains in Madrid,
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killing around 200 people and leaving more than 1,800 injured.
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Spanish authorities recovered fingerprints on a bag of detonators and
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then sent them to the FBI laboratory to help get
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the culprit. Because, as we mentioned before, the FBI has
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one of the best forensic laboratories in the world. The
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FBI ran their prints through their database of millions of
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fingerprints and it suggested 20 candidates. It was then, as usual,
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up to the FBI examiner to compare the prints found
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on the bag to potential matches. One of those 20
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potentials was an attorney based in Portland, Oregon, called Brandon Mayfield.
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The fingerprint examiner claimed there were 15 distinct points on
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Brandon's fingerprint that matched the ones on the detonator bag.
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And so the examiner said it was a match. The
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prints were then sent to three other experts and all
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00:23:54.019 --> 00:23:56.539
four of them agreed that the print on the detonator
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00:23:56.740 --> 00:24:02.619
matched Brandon's. Meanwhile, the FBI got busy rifling through Brandon's
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00:24:02.700 --> 00:24:05.740
records and surveilling him. They found out that Brandon was
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Muslim and he'd defended a convicted terrorist in a child
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custody case. Soon, Brandon was arrested. But then, around two
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weeks later, the Spanish authorities said they had found another
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match for this print. a man who, unlike Brandon, was
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actually in Spain at the time of the bombing. The
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00:24:27.009 --> 00:24:29.920
FBI admitted they screwed up. They offered him $ 2 million
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and apologised. Here's Brandon speaking after the fact.
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I honestly felt like I was being framed because I
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hadn't been out of the country for over 10 years.
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And a year and a half later, the Department of
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Justice put out a report trying to figure out what
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went wrong. Their report highlighted a couple of things. First,
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they pointed out that the prints, Brandon's and the ones
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found on the bag, had an unusual similarity. That is,
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they really did have a bunch of matching points. But
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00:25:00.170 --> 00:25:03.549
the FBI also acknowledged that there were some problems in
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their process. Like at one point in the investigation, this
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was after the initial match, the fingerprint examiners knew that
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Brandon had acted as an attorney for a convicted terrorist
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and that he was Muslim. The Department of Justice noted
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that one of the fingerprint examiners admitted that if the
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person who had been identified
had been a different kind
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of person, quote, like the Maytag repairman, end quote, the
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00:25:29.410 --> 00:25:33.450
lab might have caught the error. OK, so Brandon's prints
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apparently did look a lot like the prints on the
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00:25:35.700 --> 00:25:40.380
detonator bag. But the Department of Justice report noted that
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00:25:40.420 --> 00:25:43.869
examiners began to find more features in the fingerprints that
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00:25:43.910 --> 00:25:48.990
looked similar, which, quote, were not really there, end quote.
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What seemed to be happening was the examiners were focusing
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on similarities with the fingerprints and they were explaining away
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00:25:56.089 --> 00:25:59.519
the little differences they saw. And then when other examiners
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00:25:59.579 --> 00:26:01.900
saw the prints, they might have been influenced by what
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00:26:01.940 --> 00:26:06.279
their colleagues thought they saw. ETL has a phrase for
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when this kind of thing happens, the snowball bias effect.
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00:26:10.940 --> 00:26:13.519
It biases more and more elements and more and more
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00:26:13.559 --> 00:26:17.130
people involved. Their bias gets very, very big, like a snowball.
440
00:26:17.470 --> 00:26:20.369
That's why I call it the biased snowball effect. And
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00:26:20.470 --> 00:26:23.170
everybody is happy we sent the guilty person to jail.
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00:26:23.470 --> 00:26:26.950
So ETL watched as the FBI fumbled the Madrid bombing case,
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00:26:27.190 --> 00:26:31.230
and he couldn't stop thinking about context and bias. So
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00:26:31.289 --> 00:26:34.849
he ran a little experiment of his own. He gave
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five fingerprint examiners two sets of fingerprints. One, he said,
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00:26:39.289 --> 00:26:42.359
was Brandon Mayfield, the American accused of the Madrid bombing.
447
00:26:43.019 --> 00:26:45.299
And the other, he said, were the prints found on
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00:26:45.319 --> 00:26:49.019
the detonator bag. Now, the experts knew that this was
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00:26:49.079 --> 00:26:53.480
a high-profile case that had been bungled. So, perhaps unsurprisingly,
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00:26:53.900 --> 00:26:56.240
four out of five of these experts said that the
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00:26:56.309 --> 00:27:00.990
prints did not match. But the thing is, ETL had
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00:27:01.109 --> 00:27:04.519
tricked them. He didn't give them Brandon's fingerprints and the
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00:27:04.559 --> 00:27:08.039
prints on the detonator bag. He actually gave each examiner
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00:27:08.119 --> 00:27:11.279
a set of prints from a totally different case, an
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00:27:11.400 --> 00:27:14.240
earlier case that each examiner had worked on and had
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00:27:14.460 --> 00:27:18.369
once said were a match. This meant that thinking they
457
00:27:18.430 --> 00:27:21.329
knew the context of a case actually caused four out
458
00:27:21.349 --> 00:27:24.369
of five
examiners to change their minds about whether two
459
00:27:24.490 --> 00:27:28.500
sets of prints were a match. Now, ETL's study was
460
00:27:28.559 --> 00:27:31.960
very small, only five examiners, but it was one of
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00:27:32.019 --> 00:27:34.980
the first to look at how bias and context can
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00:27:35.019 --> 00:27:40.190
affect fingerprint analysis. Since then, other work has also demonstrated
463
00:27:40.250 --> 00:27:46.519
that fingerprint examiners can change their analysis depending on different circumstances. Now,
464
00:27:46.680 --> 00:27:49.539
it's important to note, though, that these later studies suggest
465
00:27:49.559 --> 00:27:52.680
that the impact of subjectivity is not as dramatic as
466
00:27:52.720 --> 00:27:55.720
what ETL found, with four out of five people changing
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00:27:55.759 --> 00:27:59.660
their minds. An FBI study estimates that examiners get it
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00:27:59.740 --> 00:28:04.170
wrong one in every 306 cases. Now, how you feel
469
00:28:04.269 --> 00:28:07.650
about that error rate probably depends on where you sit
470
00:28:07.710 --> 00:28:10.630
in the courtroom. But ETL doesn't want us to give
471
00:28:10.690 --> 00:28:13.650
up on fingerprints, even though he studies the problems around them.
472
00:28:13.970 --> 00:28:15.410
He remains a big fan.
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Fingerprinting is one of the best forensic science evidence.
474
00:28:23.509 --> 00:28:28.279
Conclusion. Fingerprint analysis isn't perfect. It's complicated and there is
475
00:28:28.339 --> 00:28:32.460
human judgment involved. But still, it is a pretty good
476
00:28:32.500 --> 00:28:36.240
way to identify someone. The problem is that it's not
477
00:28:36.400 --> 00:28:42.140
as infallible as many people and jurors think. Final stop,
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00:28:42.740 --> 00:28:47.509
hair analysis. On TV shows, investigators are always combing through
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00:28:47.529 --> 00:28:51.490
the crime scene, searching for that one telltale strand of hair.
480
00:28:51.509 --> 00:28:52.789
Take a look at this hair.
481
00:28:52.809 --> 00:28:55.569
I happen to catch a glimpse of this blonde hair
482
00:28:55.630 --> 00:28:56.289
in the zipper here.
483
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Hair.
484
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Detectives want to find a hair so they can match
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00:29:01.670 --> 00:29:05.849
it to a potential suspect. Here's how it works. A
486
00:29:05.890 --> 00:29:08.269
hair turns up at a crime scene. Examiners look at
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00:29:08.309 --> 00:29:10.609
it under the microscope and then they see if it's
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00:29:10.650 --> 00:29:14.569
similar to someone else's hair, like a suspect's. The idea
489
00:29:14.640 --> 00:29:17.589
is that there are teeny tiny differences within hair that
490
00:29:17.609 --> 00:29:20.569
are unique to each person. And we're not just splitting
491
00:29:20.609 --> 00:29:23.529
hairs here. This has been used in cases where people
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00:29:23.569 --> 00:29:26.829
have been put on death row. For decades, the FBI
493
00:29:26.890 --> 00:29:30.049
went around the country training hundreds of experts on how
494
00:29:30.109 --> 00:29:33.690
to compare hair samples. Here's an FBI training video from
495
00:29:33.710 --> 00:29:34.650
the 1960s.
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00:29:35.650 --> 00:29:39.809
From a microscopic examination of hairs, we can determine race,
497
00:29:40.359 --> 00:29:44.500
body area. Hairs recovered from the victim's garment can be
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00:29:44.559 --> 00:29:46.259
compared with hairs from a suspect.
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00:29:46.819 --> 00:29:49.920
The people trained by the FBI then used that expertise
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00:29:50.000 --> 00:29:53.109
in hundreds of cases, helping to put some people on
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00:29:53.200 --> 00:29:53.900
death row.
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00:29:54.630 --> 00:29:54.789
But.
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00:29:55.640 --> 00:29:58.920
What can looking at hair under a microscope really tell
504
00:29:58.960 --> 00:30:02.859
you about a suspect? Patrick Bazzini is an Associate Professor
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00:30:02.900 --> 00:30:06.400
of Forensic Science at Sam Houston State University. He told
506
00:30:06.460 --> 00:30:08.710
us that there was good science to tell the difference
507
00:30:08.789 --> 00:30:11.410
between whether a hair comes from a human, a cat
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00:30:11.509 --> 00:30:14.690
or a dog. And Patrick says this is pretty obvious
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00:30:14.769 --> 00:30:15.670
under a microscope.
510
00:30:16.329 --> 00:30:19.670
Oh, definitely, yes. I think that the microscope is really
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00:30:19.690 --> 00:30:22.750
the best instrument to make this type of determination. It's
512
00:30:22.809 --> 00:30:23.210
a must.
513
00:30:23.599 --> 00:30:25.720
Okay, so there's good science to show this is a
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00:30:25.779 --> 00:30:29.029
human hair. Where do we start getting into the bad science?
515
00:30:29.309 --> 00:30:30.529
What do you mean the bad science?
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00:30:31.390 --> 00:30:32.450
I think you know what I mean.
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00:30:32.750 --> 00:30:34.269
Yes, I was just teasing you, of course.
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00:30:34.970 --> 00:30:38.349
In 2002, a landmark study found that in 9 out
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00:30:38.369 --> 00:30:41.319
of 80 cases where hair examiners had said that two
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00:30:41.400 --> 00:30:44.819
hairs look the same under the microscope, they actually came
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00:30:44.960 --> 00:30:47.119
from different people. So that means 71 out of 80
522
00:30:47.119 --> 00:30:52.380
were right. That's not bad. if you're doing a test
523
00:30:52.440 --> 00:30:55.970
and you're in primary school, but maybe not so good
524
00:30:56.029 --> 00:30:58.230
if you're sitting in a courtroom and your life depends
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00:30:58.289 --> 00:31:01.990
on it. Is it possible to take a hair sample
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00:31:02.029 --> 00:31:05.930
from a crime scene and say, Wendy, this is your hair?
527
00:31:07.210 --> 00:31:11.230
Absolutely not. Not at least if there is the possibility
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00:31:11.269 --> 00:31:14.819
that another unknown individual may have originated that hair.
529
00:31:15.660 --> 00:31:19.299
And while there might be teeny,
seemingly special microscopic features
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00:31:19.359 --> 00:31:22.940
in my hair... There are no good big studies showing
531
00:31:23.039 --> 00:31:27.119
how unique those features really are, which means that experts
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00:31:27.180 --> 00:31:30.150
cannot say with any level of confidence that a certain
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00:31:30.230 --> 00:31:33.910
hair came from a particular person. And the Department of
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00:31:33.990 --> 00:31:37.730
Justice agrees. They acknowledge that you can't match a person
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00:31:37.829 --> 00:31:41.490
to a particular strand of hair based on microscopic evidence.
536
00:31:42.390 --> 00:31:46.829
The problem is that throughout the 1990s, courtroom experts were
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00:31:46.910 --> 00:31:50.690
claiming that they could match a hair sample to a person.
538
00:31:51.109 --> 00:31:54.410
But today, the FBI is acknowledging the problems with hair.
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00:31:55.029 --> 00:31:57.630
In June of this year, the director of the FBI
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00:31:57.670 --> 00:32:00.420
wrote a letter admitting that there were problems with how
541
00:32:00.519 --> 00:32:06.359
their examiners were talking about hair comparisons in court. He said, quote...
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00:32:06.319 --> 00:32:09.460
In many cases, we have discovered that the examiners made
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00:32:09.549 --> 00:32:12.970
statements that went beyond the limits of science in ways
544
00:32:13.009 --> 00:32:17.509
that put more weight on hair comparison than scientifically appropriate.
545
00:32:18.170 --> 00:32:21.710
End quote. Chris Fabricant from the Innocence Project says.
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00:32:21.869 --> 00:32:25.789
My favourite example is actually a favourite example from Texas.
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00:32:25.910 --> 00:32:28.170
The hair examiner in that case had said that the
548
00:32:28.210 --> 00:32:31.160
chances that somebody apart from the defendant had left the
549
00:32:31.200 --> 00:32:33.640
hair at the crime scene were slim to none and
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00:32:33.700 --> 00:32:34.619
none just left town.
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00:32:36.500 --> 00:32:38.859
As in, the hair examiner said that there is no
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00:32:38.920 --> 00:32:41.779
chance I'm wrong, I know this hair belongs to the suspect.
553
00:32:42.960 --> 00:32:45.819
The FBI is now working with the Innocence Project to
554
00:32:45.880 --> 00:32:50.799
review more than 3,000 criminal cases that used microscopic hair analysis.
555
00:32:51.380 --> 00:32:54.619
As of March last year, the FBI announced that in
556
00:32:54.619 --> 00:32:58.130
268 cases where the FBI testimony was used against a
557
00:32:58.160 --> 00:33:03.109
defendant at trial, in 96% of cases, wrong statements were
558
00:33:03.150 --> 00:33:04.710
made about hair analysis.
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00:33:04.710 --> 00:33:06.710
96%.
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00:33:06.789 --> 00:33:12.150
In 33 of those cases, people were sentenced with the
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00:33:12.230 --> 00:33:16.799
death penalty. Nine of those were executed. Five died of
562
00:33:16.880 --> 00:33:25.339
other causes while on death row. Conclusion. There's no good
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00:33:25.420 --> 00:33:28.220
scientific evidence that you can match a strand of hair
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00:33:28.299 --> 00:33:32.000
to an individual by looking at that hair under the microscope.
565
00:33:33.119 --> 00:33:33.240
So.
566
00:33:33.730 --> 00:33:37.430
When it comes to forensic science, does it stack up?
567
00:33:39.359 --> 00:33:43.440
How accurately can scientists use bugs to tell when someone died? Well,
568
00:33:43.660 --> 00:33:46.480
under ideal conditions, they can nail the time of death
569
00:33:46.619 --> 00:33:51.369
to the day. But when things are unexpected, like fire
570
00:33:51.470 --> 00:33:56.650
ants or cocaine, the science can get messy. Bite marks.
571
00:33:57.029 --> 00:33:59.470
Can you match a bite mark to a suspect's set
572
00:33:59.529 --> 00:33:59.950
of teeth?
573
00:34:00.839 --> 00:34:01.099
No.
574
00:34:02.539 --> 00:34:04.799
Teeth haven't been shown to be that unique and the
575
00:34:04.839 --> 00:34:09.199
bite marks that they make are even less unique. Fingerprints,
576
00:34:09.469 --> 00:34:13.010
how reliable are they? Most of the time, fingerprint examiners
577
00:34:13.110 --> 00:34:16.269
get it right, but they're not perfect and human judgement
578
00:34:16.510 --> 00:34:20.530
is involved. And hair, can you pin a suspect based
579
00:34:20.630 --> 00:34:26.369
on a microscopic analysis of their hair? Nope. Science is
580
00:34:26.449 --> 00:34:29.090
not good enough to see hair under a microscope... and
581
00:34:29.159 --> 00:34:33.980
match it to a particular person. But hair is very
582
00:34:34.119 --> 00:34:38.179
useful in other ways. There's a goldmine of information in
583
00:34:38.219 --> 00:34:41.019
the DNA of hair and that can pin a suspect
584
00:34:41.179 --> 00:34:44.820
to a crime. DNA has in fact become the gold
585
00:34:45.019 --> 00:34:48.119
standard of forensic science and there's good science behind it
586
00:34:48.179 --> 00:34:52.300
with clear statistical certainty. DNA has been used to put
587
00:34:52.380 --> 00:34:55.119
guilty people away and set innocent people free.
588
00:34:56.320 --> 00:34:56.530
But.
589
00:34:57.409 --> 00:35:01.530
Forensic scientists have now started pushing the boundaries of what
590
00:35:01.710 --> 00:35:05.800
DNA evidence can do. They're able to extract tiny amounts
591
00:35:05.860 --> 00:35:09.400
of genetic evidence from doorknobs, coffee mugs and even weapons
592
00:35:09.860 --> 00:35:12.420
in a way that just wasn't possible decades ago. A
593
00:35:13.380 --> 00:35:18.780
new generation of forensic science is upon us. But is
594
00:35:18.820 --> 00:35:23.050
it any better than the old stuff? That's coming up
595
00:35:24.269 --> 00:35:28.969
next time on Science Versus. We'll be back with part
596
00:35:29.070 --> 00:35:33.239
two of Science vs Forensic Science in two weeks. And
597
00:35:33.280 --> 00:35:37.679
when we do, we're getting our hands really dirty. So
598
00:35:37.880 --> 00:35:39.340
is this person wearing a shirt?
599
00:35:39.719 --> 00:35:42.000
No, that is what the flesh ends up looking like
600
00:35:42.059 --> 00:35:43.460
throughout the decomposition process.
601
00:35:43.519 --> 00:35:45.820
It looks like they're wearing clothes, but it's actually skin.
602
00:35:46.539 --> 00:35:49.760
This episode has been produced by Shruti Ravindran, Diane Wu,
603
00:35:50.119 --> 00:35:53.940
Austin Mitchell, Heather Rogers and Caitlin Kenney. Our senior producer
604
00:35:54.039 --> 00:35:58.420
is Caitlin Soarey. edited by Annie Rose Strasser, fact-checking by
605
00:35:58.440 --> 00:36:02.239
Michelle Harris. Sound design and music production is by Matthew Boll.
606
00:36:02.360 --> 00:36:04.900
This has been mixed by Martin Peralta and Bobby Lord.
607
00:36:05.320 --> 00:36:09.710
Music written by Bobby Lord. I'm Wendy Zuckerman. Fact you
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00:36:09.750 --> 00:36:10.110
next time.