Speaker 1: Get in touch with technology with tech Stuff from how
Speaker 1: stuff Works dot com. Hey there, and welcome to tech Stuff.
Speaker 1: I am your host, Jonathan Strickland. I'm an executive producer
Speaker 1: with how Stuff Works in I love all things tech,
Speaker 1: though today we're gonna be talking about a branch of
Speaker 1: technology that gets up. I'm pretty grim and pretty serious. Uh,
Speaker 1: this is a listener request. Listener Hakim asked that I
Speaker 1: do an episode about forensic technology, so I'm actually gonna
Speaker 1: do a pair of episodes. It is fascinating stuff and
Speaker 1: it's definitely not quite the same as what we see
Speaker 1: in depictions on film or in television shows. That's not
Speaker 1: a big surprise. We've covered multiple times how technology in
Speaker 1: pop culture is very different from what we see in reality.
Speaker 1: But in this episode, I'm going to specifically focus on
Speaker 1: the history of forensics, and in the next episode we'll
Speaker 1: talk about some of the cutting edge technologies that are
Speaker 1: used in for psick investigations today. So forensics, first of all,
Speaker 1: has a few different definitions. If you are being very literal,
Speaker 1: it can mean debate or discussion in Latin, but as
Speaker 1: we tend to use it today, we refer to it
Speaker 1: as the science with regard to detecting and solving crimes.
Speaker 1: So not just if a crime has occurred, but how
Speaker 1: did a crime occur, how did it unfold in time,
Speaker 1: who was involved? That sort of stuff. And like all sciences,
Speaker 1: forensics can trace its history back far before the formal
Speaker 1: codification of the scientific method, and this involves lots of
Speaker 1: different ideas and processes for different elements of investigation developing
Speaker 1: at various times throughout history. Like most things, forensics involved
Speaker 1: a lot of different ideas being tested throughout centuries before
Speaker 1: maturing as a collection of practices. So one of the
Speaker 1: easy ideas we can talk about, because there are a
Speaker 1: lot of different independent threads that converge to become forensics.
Speaker 1: On easy entry point is a discussion about fingerprints and
Speaker 1: developing the skills and technology to detect and identify them
Speaker 1: and classify them in the context of criminal investigations. Now,
Speaker 1: I've done a full episode on fingerprinting in the past,
Speaker 1: so I'll give more of a short overview of the
Speaker 1: whole thing here. There are records that actually indicate that
Speaker 1: handprints were used as evidence and investigations for burglary back
Speaker 1: in China more than two thousand years ago, and the
Speaker 1: book with the English title Universal History, which was published
Speaker 1: in Persia in the th hundreds, mentioned the practice of
Speaker 1: identifying people based upon their fingerprints. European anatomists and philosophers
Speaker 1: made observations about fingerprints in the seventeenth century, but those
Speaker 1: observations weren't really connected to the idea that fingerprints themselves
Speaker 1: are unique to specific individuals and that no two people
Speaker 1: would share the same ones. J. C. A. Meyer, a
Speaker 1: German anatomist, published Anatomical Copper Plates with Appropriate Explanations. That's
Speaker 1: the actual title of the book, Anatomical Copper Plates with
Speaker 1: Appropriate Explanations, in sounds like it was a rip roaring
Speaker 1: picture book anyway. He described fingerprints as being unique, but
Speaker 1: also noted that they can appear similar to one another. So,
Speaker 1: in other words, on close examination you will see that
Speaker 1: they are unique, but on casual glance you may not
Speaker 1: be able to make that distinction easily. The nineteenth century
Speaker 1: saw a lot more work to define the qualities of
Speaker 1: fingerprints and how to classify them. How would you describe
Speaker 1: the fingerprints, how would you describe the grooves in such
Speaker 1: a way that it made sense? And then how would
Speaker 1: you classify fingerprints so that you could kind of categorize them,
Speaker 1: and how would you preserve impressions of them. All of
Speaker 1: these were ideas and practices that were developed in the
Speaker 1: eighteen hundreds. By the end of that century, Mark Twain
Speaker 1: was incorporating the idea of using fingerprints to identify a
Speaker 1: murderer and a couple of his books, And right at
Speaker 1: the cusp of the twentieth century, just before nineteen hundred,
Speaker 1: you had organizations starting to build out fingerprint files for
Speaker 1: the purposes of identifications. So the idea of using fingerprints
Speaker 1: to uh to ascertain the identity of someone you know
Speaker 1: they've left a fingerprint behind a scene, that had really
Speaker 1: started to take hold by the late nineteenth century, says
Speaker 1: the Sherlock Holmes era. The twentieth century saw a rapid
Speaker 1: development of technology in all different fields. Right, we see
Speaker 1: in the nineteen hundreds crazy amounts of innovation in all
Speaker 1: sorts of industries. But that included eventually things like digitizing
Speaker 1: records of fingerprint files, which would allow law enforcement to
Speaker 1: create the automated fingerprint identification system. And now in the
Speaker 1: United States, the Department of Homeland Security oversees a database
Speaker 1: containing more than one twenty million people's fingerprints. The FBI
Speaker 1: conducts more than three hundred thousand KORD searches per day
Speaker 1: against more than one forty million computerized fingerprint records. Uh
Speaker 1: some of those are criminals, some of those are civil,
Speaker 1: and so like civil fingerprints, you might have to submit
Speaker 1: for fingerprinting at when getting a a an i D
Speaker 1: like a state issued i D for example in the
Speaker 1: United States. The world's largest database of fingerprint information, not
Speaker 1: just fingerprint but biometric in general, actually belongs to a
Speaker 1: company called the Unique Identification Authority of India. It's really
Speaker 1: more of an organization, I guess I should say so
Speaker 1: that also includes face and biometric records and the goal
Speaker 1: to provide all one point to five billion residents of
Speaker 1: India with the option to record their biometric data for
Speaker 1: the purposes of providing reliable national i D documents. Participation
Speaker 1: in that database, by the way, is voluntary, so they
Speaker 1: aren't forced to submit to this uh In the citizens
Speaker 1: of India can opt into this system for the purposes
Speaker 1: of making it easier to get these kinds of national ideas.
Speaker 1: So that's the idea behind fingerprinting. This this concept of
Speaker 1: being able to look at the loops in the worlds
Speaker 1: and the various ridges and to compare them against a
Speaker 1: large database to see if there's a match. There were
Speaker 1: very familiar with that, and like I said, I did
Speaker 1: a full episode. So if you want to learn way
Speaker 1: more about the process of fingerprinting and identification through fingerprinting,
Speaker 1: go through the text of archives. There's an episode just
Speaker 1: about that. So let's move over to ballistics. Now, technically,
Speaker 1: ballistics is the science of projectiles and firearms. Within the
Speaker 1: context of forensics. We tend to use the term ballistics
Speaker 1: to talk about the various aspects of an investigation into
Speaker 1: a crime that included a gun being fired at least once,
Speaker 1: and a lot can go into that. One person I
Speaker 1: need to mention is a guy named Henry Goddard, and
Speaker 1: there actually were a couple of Henry Goddard's, So I'm
Speaker 1: not talking about the American psychologist who advocated for intelligence
Speaker 1: testing in the early twentieth century. I'm instead talking about
Speaker 1: a nineteenth century member of London's Bow Street Runners. And
Speaker 1: holy cow, this is a group that needs coverage in
Speaker 1: a show like Ridiculous History, not because it's ridiculous, but
Speaker 1: because it is fascinating. This is one of those things
Speaker 1: where I had heard about the Bow Street runners, but
Speaker 1: I hadn't really looked into it. And by the way,
Speaker 1: if someone comes in to tell me that no, it's
Speaker 1: Bow Street in London and Bow Street not Bow Street,
Speaker 1: I apologize. That's my American ignorance showing through. I'm gonna
Speaker 1: go with Bow Street because that's just how I assumed
Speaker 1: it was pronounced, but I fully admit it could be wrong.
Speaker 1: So quick history lesson. Leading up to the late seventeen hundreds,
Speaker 1: it was customary in London that if you happen to
Speaker 1: be a man, you were expected to participate in the
Speaker 1: policing of your own community. So if you saw a
Speaker 1: crime being commit did you were expected to intervene in
Speaker 1: that crime and apprehend the perpetrator and convict that person.
Speaker 1: You were also expected to send serve time in the
Speaker 1: night watch, which meant that between the hours of say
Speaker 1: eight or nine PM and dawn, you would have to
Speaker 1: patrol streets and make sure that that there were no
Speaker 1: suspicious people lurking about, or that if anyone was seen
Speaker 1: on the streets, that they had a valid reason to
Speaker 1: be out there and they weren't up to no good.
Speaker 1: And a lot of people were starting to get a
Speaker 1: little nervous about this because by the seventeen hundreds you
Speaker 1: had a new class that had formed in London. And
Speaker 1: previously you had the commoners and you had the nobility,
Speaker 1: and that was the way of things in the in
Speaker 1: England for quite some time. Uh and then by the
Speaker 1: Renaissance you were starting to see the rise of the
Speaker 1: middle class, and by the seventeen hundreds you the upper
Speaker 1: middle class. You had people who were wealthy. They weren't noble,
Speaker 1: but they owned a lot of wealth, whereas you had
Speaker 1: nobility that were they had noble titles, but some of
Speaker 1: them weren't very wealthy at all. So this really created
Speaker 1: confusion in England, where for the longest time social status
Speaker 1: was based upon nobility, and nobility tended to bring wealth
Speaker 1: along with it. Anyway, you had these upper class folks
Speaker 1: in London, men who were not terribly keen on the
Speaker 1: idea of having to patrol their city streets and getting
Speaker 1: involved in altercations that could involve violent criminals. You think,
Speaker 1: I didn't work so hard to become so successful to
Speaker 1: potentially get my skull caved in by a villain with
Speaker 1: a club. So I'm going to hire someone to go
Speaker 1: in my place, and people started to hire deputies. Well.
Speaker 1: Around the same time, royal proclamations had created a reward
Speaker 1: system for people who helped keep the peace by convicting
Speaker 1: criminals of various crimes, including various thefts, so this gave
Speaker 1: rise to an unofficial occupation called thief taker. Thief takers
Speaker 1: would often not just make money by pursuing convictions of criminals,
Speaker 1: but also essentially selling back stolen property to the rightful owners.
Speaker 1: So they would get money by putting the thief behind
Speaker 1: bars and get more money by selling the stolen property
Speaker 1: back to the person who owned in the first place.
Speaker 1: So then you had Henry and John Fielding and they
Speaker 1: had a house on Bow Street. Henry Fielding started to
Speaker 1: pay retainers to men who were either constables or ex
Speaker 1: constables to locate and arrest criminals, particularly violent criminals, and
Speaker 1: if you did that, you were entitled to the reward.
Speaker 1: So if you were one of the members of the
Speaker 1: Bow Street Runners and you apprehended someone, you convicted that
Speaker 1: person of a crime, you would get the reward there
Speaker 1: and the Fieldings hope that what they could do is
Speaker 1: managed this group and rain in any corruption to keep
Speaker 1: things on the level, and they essentially became a private
Speaker 1: police force of sorts, and over time they developed processes
Speaker 1: and procedures that would become the foundation of modern policing
Speaker 1: in many ways. Now, Goddard, who had mentioned before, was
Speaker 1: one of these bow street runners or policemen, and he
Speaker 1: identified a murderer in eighteen thirty five by linking a
Speaker 1: bullet recovered from a victim to the person who made
Speaker 1: the bullet, because in those days most people who owned
Speaker 1: guns made their own bullets. You did this by pouring
Speaker 1: molten lead into a two piece mold, to set it
Speaker 1: into that mold, and then you would, you know, forge
Speaker 1: a bullet. Goddard saw in the bullet, and imperfection that
Speaker 1: he reasoned was from the manufacturing process, which meant the
Speaker 1: mold itself would have evidence of that fault, and if
Speaker 1: you were to mold another bullet with that mold, you
Speaker 1: should be able to replicate the fault in it. So
Speaker 1: Goddard was able to get a confession from the suspect
Speaker 1: and one to convict action. It was only later that
Speaker 1: people pointed out his approach was not necessarily the most scientific,
Speaker 1: as similar molds could have produced a similar looking bullet.
Speaker 1: But it was an early example of ballistics and forensics.
Speaker 1: It's just it wasn't a terribly scientifically solid one. But
Speaker 1: you flash forward a century later and then you have
Speaker 1: Calvin Goddard, but no relation to Henry Goddard, whom I
Speaker 1: just talked about. Calvin Goddard was a scientist, a researcher,
Speaker 1: and a military officer, and in nineteen five he wrote
Speaker 1: an article titled Forensic Ballistics and described using a special
Speaker 1: type of microscope he had created called a comparison microscope
Speaker 1: when examining side by side specimens. Now, essentially a comparison
Speaker 1: microscope is too light. Microscopes connected by an optical bridge.
Speaker 1: So there are two uh ocular lenses, two eye pieces,
Speaker 1: so you look in one with each giant. It looks
Speaker 1: almost like binoculars, excepted some microscope. And it meant that
Speaker 1: you could put a sample under one and a sample
Speaker 1: under the second one, and pair of the two in
Speaker 1: a single view. And he used it to compare bullet
Speaker 1: casings or bullet shells and bullets recovered from crime scenes,
Speaker 1: and by being able to see both a bullet and
Speaker 1: it's casing, he could verify whether or not the bullet
Speaker 1: actually belonged to that casing by the markings. He could
Speaker 1: also if say you had recovered a firearm from a
Speaker 1: suspect and you were wondering if it was the same
Speaker 1: firearm as the one used in a crime, you could
Speaker 1: fire that into a soft target, retrieved the bullets, compare
Speaker 1: them side by side, so uh that would allow you
Speaker 1: to look at them in real time next to each
Speaker 1: other at a microscopic level. Previously, what you would have
Speaker 1: to do is look at one like the actual one
Speaker 1: that was found at the scene of a crime, and
Speaker 1: make note of any indentations or markings on the bullet,
Speaker 1: and then you would look at a second one separately.
Speaker 1: But that men, you had to rely upon your memory
Speaker 1: in part to make this comparison in and memories are faulty,
Speaker 1: so his technology would end up playing a vital role
Speaker 1: in several early twentieth century investigations, including the investigation into
Speaker 1: the infamous St. Valentine's Day massacre. Goddard was able to
Speaker 1: prove that the bullets that were fired in that crime
Speaker 1: did not come from police guns because the men who
Speaker 1: committed the murders were wearing Chicago police uniforms when they
Speaker 1: did it, but they said, well, no, these didn't come
Speaker 1: from the guns that belonged to police officers. Later on
Speaker 1: they were able to discover a gun that belonged to
Speaker 1: a mobster that did match the bullets that were fired
Speaker 1: during the St. Valentine's Day masacre. So it was one
Speaker 1: of the guns used in that terrible, terrible event. They
Speaker 1: were figured out it wasn't vigilante justice at all, it
Speaker 1: was a mob hit. Based upon the evidence, Godard would
Speaker 1: be asked to become the head of the first independent
Speaker 1: forensics science crime Lab, which was at Northwestern University in
Speaker 1: nineteen twenty nine. The lab later became known as the
Speaker 1: Scientific Crime Detection Laboratory of h AGO. Very influential lab.
Speaker 1: Now get a lot more to say about forensics science
Speaker 1: and its development over the years, but first let's take
Speaker 1: a quick break to thank our sponsor. One of the
Speaker 1: many things a ballistics expert in forensic studies would look
Speaker 1: at would be those marks left on a bullet after
Speaker 1: it has been fired from a gun. Modern guns have
Speaker 1: rifling in the barrels, which refers to grooves that are
Speaker 1: inside the barrel. They're meant to produce torque on a bullet,
Speaker 1: which forces the bullet to spin as it travels down
Speaker 1: the barrel, and it continues spinning when it emerges because
Speaker 1: a spinning projectile has a much more stable flight path
Speaker 1: due to behaving like a gyroscope. I talked about gyroscopes
Speaker 1: in recent episodes of tech Stuff. Essentially because of the
Speaker 1: conservation of angular momentum and objects spinning around an access
Speaker 1: of rotation resists changes in its orientation, so a spinning
Speaker 1: bullet will remain more true to its flight path. And
Speaker 1: a projectile fired from a smooth bore firearm which has
Speaker 1: no rifling on the inside of its gun barrel, but
Speaker 1: passing down this groove path essentially carves a pattern on
Speaker 1: a bullet. A bullets diameter is slightly larger than the
Speaker 1: board diameter of the barrel it is fired through. The
Speaker 1: bullet is of a softer material, so it will end
Speaker 1: up getting a pattern carved into it as it as
Speaker 1: as it's forced on this barrel at high velocity and
Speaker 1: begins to go into the spin. Investigators can actually count
Speaker 1: the number of grooves or impressions around the circumference of
Speaker 1: the bullet, and by looking down the length of a
Speaker 1: bullet from behind, the investigators can determine the twist direction
Speaker 1: of the rifling grooves inside the barrel, and this part
Speaker 1: of a gun barrel can wear down after use. That
Speaker 1: means that the patterns will end up being unique to
Speaker 1: specific guns. Even if you have two guns that are
Speaker 1: the same make and model, the wear pattern is going
Speaker 1: to be different for both of those so you will
Speaker 1: end up have different patterns actually imparted to the bullets
Speaker 1: fired out of those guns. So if investigators can retrieve
Speaker 1: bullets from a scene, they can potentially match those bullets
Speaker 1: to a specific firearm, assuming they also have possession of
Speaker 1: that firearm to compare the two, or they can use
Speaker 1: the patterns to potentially eliminate firearms that could not have
Speaker 1: produced those patterns. So, like I said before, the way
Speaker 1: you would typically do this is you have the suspect firearm,
Speaker 1: you fired it a few times, and you fire it
Speaker 1: into into a target that will preserve the integrity of
Speaker 1: the bullets. It's not designed to have the bullet break apart.
Speaker 1: So that way you have as good a sample as
Speaker 1: you possibly can. You compare the patterns on that bullet
Speaker 1: to the one that you have retrieved from the crime scene,
Speaker 1: and you look and see if they they are in
Speaker 1: fact similar enough to say they were both fired from
Speaker 1: the same weapon. Uh. Firearms also produced marks on cartridge cases,
Speaker 1: and no two firearms will do so exactly the same way.
Speaker 1: So cartridges will bear markings, they're different from rifling markings.
Speaker 1: They they might have something like a firing pin, Ambrussians,
Speaker 1: breach marks, extractor marks, and dejector marks. Depending upon the
Speaker 1: type of firearm you're talking about, surface characteristics created on
Speaker 1: the firearm itself from use will give it a uniqueness
Speaker 1: that other firearms won't reproduce. That's that where in Taro
Speaker 1: is telling you about um. But firearms also don't change
Speaker 1: super quickly, right. They do wear down over time, but
Speaker 1: it's not super super fast. Even if two are the
Speaker 1: same make and model, you're gonna have slight differences, like
Speaker 1: I said before, But they don't change so fast that
Speaker 1: you have to worry about identifying a gun. Well after
Speaker 1: a crime is committed, let's say that you have retrieved
Speaker 1: a bullet from the case of the crime scene, and
Speaker 1: let's say it's a cold case, like it's the case
Speaker 1: has gone cold and it's essentially shelved. And then later
Speaker 1: on you come across somebody and you're like I like
Speaker 1: this guy for that crime we never solved, you know,
Speaker 1: fifteen years ago, and this guy even had a gun
Speaker 1: that would have fired the bullets. It's the same style
Speaker 1: of gun that we suspect fired the bullets that we
Speaker 1: retrieved at that scene. Even though fifteen years have passed.
Speaker 1: You can fire that suspects gun and you can compare
Speaker 1: it against the bullet you retreat from the crime scene,
Speaker 1: and chances are there won't be so much wear and tear.
Speaker 1: Assuming it is the same gun, that you would be
Speaker 1: able to say, oh, it's the exact same firearm. So
Speaker 1: if you fire a gun once and you retreat the bullet,
Speaker 1: then you fire at ninety nine more times and you
Speaker 1: treat the one bullet, there should still be enough similarities
Speaker 1: between bullets one and one hundred for you to say
Speaker 1: they both definitely came from the same gun. In addition
Speaker 1: to studying bullets to determine if they were fired from
Speaker 1: a specific firearm, forensic investigators also examined bullet holes left
Speaker 1: it scenes to figure out where the person firing the
Speaker 1: gun was standing and how tall he or she was.
Speaker 1: Based on the evidence, the shape of a bullet hole
Speaker 1: gives us a lot of information. So some people might say, go,
Speaker 1: bullet holes are gonna be around, Well, that's not true
Speaker 1: unless the person firing the gun is firing at perfectly
Speaker 1: level at a ninety degree angle to whatever the surfaces
Speaker 1: that that ends up being hit by the bullet. Otherwise
Speaker 1: you're gonna get an elliptical shape from the bullet hole,
Speaker 1: and that elliptical shape will tell you a lot. It's
Speaker 1: it's angled, it will show that the bullet hit the
Speaker 1: wallet to bias. So you can determine the angle from
Speaker 1: which the bullet entered the wall, and if you have
Speaker 1: a suspect, you can use geometry to determine if that
Speaker 1: suspect could have been responsible. Not necessarily if they did
Speaker 1: or didn't do it, but you can at least say, well,
Speaker 1: is it possible that they did it. This is where
Speaker 1: you look at, say, bullet holes in the wall. You
Speaker 1: determine the angle from where the bullet entered the wall.
Speaker 1: You've figured out where what distance from the wall the
Speaker 1: shooter was, and you say, well, if the shooter was
Speaker 1: five ft ten, this makes sense. But if you start
Speaker 1: getting too short or too tall from that, then it wouldn't.
Speaker 1: The angle doesn't make any that's based upon what we know.
Speaker 1: So let's say that you've got a four ft three
Speaker 1: inch tall suspect. You might say, well, there's no way
Speaker 1: this person is too short for that to have worked
Speaker 1: out the way we believe it did. So that those
Speaker 1: bullet holes can tell you a lot of information, but
Speaker 1: you have to use geometry in order to do it,
Speaker 1: which means I would be really bad at it. I
Speaker 1: was terrible at geometry. It's great at trigonometry, but not
Speaker 1: so much at geometry. Anyway, these days, investigators may use
Speaker 1: advanced technologies like laser scanners to get really precise information
Speaker 1: from a crime scene in order to create a simulation
Speaker 1: to to view things like the angle of fire and
Speaker 1: the distance and that sort of stuff. I'll talk more
Speaker 1: about that in the next episode. However, other science and
Speaker 1: technology that relates to crimes in which a gun was
Speaker 1: fired might include detecting residue from gunshots. By the nineteen seventies,
Speaker 1: scientists started using scanning electron microscopes to do at I
Speaker 1: also talk about scanning electron microscopes in the next episode
Speaker 1: and talk about how those work. It's pretty fascinating stuff.
Speaker 1: But forensics goes beyond fingerprints and ballistics in the eighteen thirties,
Speaker 1: there was a chemist named James Marsh who developed a
Speaker 1: chemical test we called the Marsh test and it was
Speaker 1: specifically to detect the presence of arsenic and he developed
Speaker 1: the test after he determined the prevailing methodology was inferior
Speaker 1: after a pretty upsetting incident in his life and all
Speaker 1: had to do with a murder trial. In two there
Speaker 1: was a man who stood accused of having murdered his
Speaker 1: grandfather by poisoning his granddad's coffee with arsenic and James
Speaker 1: Marsh was called upon to do an investigation and present
Speaker 1: his findings to court, and he was meant to test
Speaker 1: the coffee for arsenic. Now, the standard at the time
Speaker 1: was that you would pass hydrogen sulfide through a sample
Speaker 1: fluid and that would create a reaction that would release hydrogen.
Speaker 1: The hydrogen would carry particles of arsenic as it bubbled
Speaker 1: up through the sample. And it's in gas form, so
Speaker 1: it passes through you know it'll it would just dissipate
Speaker 1: if you didn't have anything else attached to it. But
Speaker 1: you would have your your device set up so that
Speaker 1: the gas is passing through a line like a glass
Speaker 1: tube for example, and you would heat the tube, and
Speaker 1: you would also burn off the hydrogen as it came
Speaker 1: out the other end of the two and traces of
Speaker 1: arsenic would remain as a precipitate that would be collected
Speaker 1: and you could use it what they would call an
Speaker 1: arsenic mirror and create the sort of blackish uh finish
Speaker 1: on a surface. But the problem was it wouldn't keep indefinitely.
Speaker 1: So Marsh conducts this test. He detects arsenic in the coffee,
Speaker 1: but by the time he was called to present to
Speaker 1: the jury, the evidence he had collected had deteriorated, and
Speaker 1: it deterior to the point where the jury didn't see
Speaker 1: the evidence, so they suspect was ultimately released of charges,
Speaker 1: and Marsh figured there had to be a better way,
Speaker 1: so he developed what we now call the Marsh test,
Speaker 1: and he stuck with a chemical reaction approach. He experimented,
Speaker 1: and he found that if he combined a sample that
Speaker 1: had arsenic in it and he put that in with
Speaker 1: some zinc that had no arsenic in it at all,
Speaker 1: arsenic free zinc, and then added sulfuric acid, it would
Speaker 1: create arsene gas, and burning off that gas would produce
Speaker 1: pure metallic arsenic and if that were to come in
Speaker 1: contact with a cold surface, it would leave behind a
Speaker 1: silvery black coating. And it was a sensitive enough test
Speaker 1: that could detect quantities of arsenic as small as one
Speaker 1: of a milligram, which is pretty nifty. Now, if there
Speaker 1: were no arsenic in the sample, you wouldn't produce this gas,
Speaker 1: so you wouldn't have that silvery residue. So chemical analysis
Speaker 1: is another important part of ensics science, and arsenic is
Speaker 1: just one of dozens of different chemicals investigators might have
Speaker 1: to search for at a crime scene. Another important element
Speaker 1: in forensics has to do with blood. Clearly, that becomes
Speaker 1: a very important element in investigations. During the nineteenth century,
Speaker 1: Dr Ludwig Carl Tichman developed a test to determine if
Speaker 1: a stain actually was dried blood or maybe it's mud
Speaker 1: or something else. And this is a test we call
Speaker 1: the Tychman test. Tend to name things after the people
Speaker 1: who proposed them. So Dr Tychman researched how organic compounds
Speaker 1: contained in human blood could crystallize. One of those compounds
Speaker 1: is called human and so Tychman developed a test in
Speaker 1: which he used a strong acetic acid, which is present
Speaker 1: in stuff like vinegar, for example, and you combine that
Speaker 1: with dried blood, and that would form human crystals. The
Speaker 1: reaction between the to acid and the blood would make
Speaker 1: these Heman crystals form. So if you're investigating a crime
Speaker 1: and you see some stains that could be dried blood,
Speaker 1: but you're not sure, you could use the Tykeman test
Speaker 1: and confirm that suspicion. It doesn't tell you what type
Speaker 1: of blood it is, it doesn't let you classify it
Speaker 1: in any way, but it would let you at least
Speaker 1: verify that in fact, the stain you're looking at is
Speaker 1: composed at least in part by blood. So if no
Speaker 1: Heman crystals formed as a result, you could disregard the
Speaker 1: stain and just say, well, I don't know what it is,
Speaker 1: but it sure ain't blood. In nineteen o one, and
Speaker 1: Austrian scientists named Carl Lnsteiner was studying blood and why
Speaker 1: sometimes when blood from one individual would be given to
Speaker 1: another individual, the blood would clump together in a process
Speaker 1: called a glutination. The clumping could create toxic reactions, which
Speaker 1: made transfusions really dangerous, and physicians have been practicing transfusions
Speaker 1: for quite some time, but no one was really sure
Speaker 1: up to that point why some transfusions seem to work
Speaker 1: and other transfusions would lead to pretty nasty outcomes, sometimes death.
Speaker 1: Landstein Are discovered that the clumping was an immunological reaction,
Speaker 1: and it was when the receiver of a blood transfusion
Speaker 1: has antibodies against components inside the donor blood, and that
Speaker 1: led to the discovery of different protein molecules within different
Speaker 1: types of blood and ultimately lead to classifying blood into
Speaker 1: groups such as A, B, A B, and OH. So,
Speaker 1: if you have type A blood, you have A antigens
Speaker 1: and BE antibodies, meaning you can accept A blood, but
Speaker 1: you cannot accept BE blood because you would react very
Speaker 1: poorly to that. Um BE blood is the opposite. You
Speaker 1: have BE antigens and A antibodies, and then A B.
Speaker 1: You have both A and B engines and antibodies. You're
Speaker 1: You're the universal received You can receive blood from any donor,
Speaker 1: and then type OH you lack the antigens and antibodies.
Speaker 1: You're the universal donor. Or. You really you don't have
Speaker 1: the antigen so you don't have to worry about uh. Like,
Speaker 1: if you're an donor, you can donate blood to anyone.
Speaker 1: Anyone can accept oh blood, though you can only accept
Speaker 1: OH blood in return fun times. Lensteiner would win a
Speaker 1: Nobel Prize in nineteen thirty for his work, and forensic
Speaker 1: scientists had a new way to examine blood to help
Speaker 1: them narrow down suspects or differentiate between a victim's blood
Speaker 1: and the blood of a suspect. Up to that point,
Speaker 1: you couldn't be sure. You might come up on a
Speaker 1: crime scene and it might be blood on the crime scene,
Speaker 1: but you don't know how much of that belonged to
Speaker 1: the victim, and and if what if any of it
Speaker 1: belonged to someone else. This allowed for testing of different proteins,
Speaker 1: which would tell you, oh, this is a type A
Speaker 1: versus type B, and would tell you if more than
Speaker 1: one person's blood were present at a crime scene. So
Speaker 1: very a useful, especially later on when you are looking
Speaker 1: up potentially identifying someone, although keep in mind the percentages
Speaker 1: of people with specific types of blood are such that
Speaker 1: you can't narrow it down to a specific individual. Just
Speaker 1: because a person might have the same blood type as
Speaker 1: blood found at the scene of a crime doesn't necessarily
Speaker 1: mean that the blood came from that person, because lots
Speaker 1: of people have those blood types it would take more
Speaker 1: specific evidence to be able to narrow that down. I'll
Speaker 1: talk more about that in a second, but first let's
Speaker 1: take another quick break to thank our sponsor. In h
Speaker 1: o Albrecht was experimenting with a chemical called luminol, a
Speaker 1: luminescent chemical, and he was experimenting with it in a
Speaker 1: solution of hydrogen peroxide, and he discovered that blood would
Speaker 1: increase the luminescence of luminol, which means it would it
Speaker 1: would cause the luminol to glow brighter. Later, other scientists
Speaker 1: determined that hematin, a pigment in blood that contains iron
Speaker 1: in it, was reacting with this luminol chemically and that
Speaker 1: chemical reaction was creating this brighter luminescence, and that became
Speaker 1: useful in forensic investigations when investigators were looking for trace
Speaker 1: amounts of blood at a scene it may not be
Speaker 1: easily visible, or maybe that someone tried to clean it up,
Speaker 1: because luminol can actually detect those trace evidence leavings of
Speaker 1: blood even if someone tried to clean stuff up. It
Speaker 1: does require making the crime scene as dark as possible
Speaker 1: so you can detect the luminescence and the glow lasts
Speaker 1: for less than a minute. But if you do a
Speaker 1: quick spritzing of luminol and hydrogen peroxide as a solution
Speaker 1: against the same spot, it will glow again. It doesn't
Speaker 1: exhaust the supply of iron necessarily on one spritzing, so uh,
Speaker 1: if you see a glow, you can reapply LIE. By
Speaker 1: the nineteen eighties, scientists were starting to develop practical tests
Speaker 1: that could analyze DNA for the purposes of forensic tests.
Speaker 1: And DNA is d ox a ribonucleic acid, which is
Speaker 1: the carrier of genetic information. I'm pretty sure you all
Speaker 1: are familiar with that, but it always is good to
Speaker 1: just kind of jump on that again. DNA contains the
Speaker 1: fundamental genetic identifiers that can be of crucial importance in
Speaker 1: an investigation. Now, most of your DNA matches my DNA,
Speaker 1: or the person in closest proximity to you, or the
Speaker 1: person most far away from you possible. We share an
Speaker 1: enormous amount of common DNA. The differences between individuals between
Speaker 1: humans are carried by about three million bases in our DNA.
Speaker 1: That that's equivalent to about one tenth of one per
Speaker 1: cent of all our DNA. So the vast majority of
Speaker 1: our DNA is identical to each other. It's only that
Speaker 1: one tenth of one percent that makes you you, which
Speaker 1: is kind of cool and and interesting. Those differences can
Speaker 1: help eliminate a suspect from an investigation, or it can
Speaker 1: help support a case for investigating the matter further if
Speaker 1: there's a match. DNA comes from organic material like blood
Speaker 1: or body fluids, from skin, from hair, stuff like that.
Speaker 1: The development of polymerase chain reaction or PCR techniques helped
Speaker 1: with DNA investigations a lot. PCR is a method for
Speaker 1: copying specific DNA regions in vitro that means in a
Speaker 1: test too, as opposed to in an organism. PCR is
Speaker 1: used for lots of different stuff, not just forensic investigations
Speaker 1: because it allows you to copy and duplicate DNA, but
Speaker 1: in forensics it can be used to make copies of
Speaker 1: sample DNA for analysis to compare DNA gathered at a
Speaker 1: crime scene with DNA from like a suspect. Some crime
Speaker 1: scenes may only have small samples of DNA that you
Speaker 1: can work with, so it's important to be able to
Speaker 1: duplicate that DNA in order for you to have enough
Speaker 1: of a sample size to run your various analyzes. In
Speaker 1: nineteen nine, DNA evidence was used to exonerate a man
Speaker 1: named Gary Dotson who had been convicted of rape in
Speaker 1: the late nineteen seventies. Kathleen Crowell, who was the presumed
Speaker 1: victim of this crime, ended up later saying she had
Speaker 1: actually made up a story about being raped. What had
Speaker 1: happened was that she and her boyfriend had engaged in
Speaker 1: consensual sex, but she was worried that she might end
Speaker 1: up pregnant, and she was terrified of what that would mean.
Speaker 1: She was a teenager at the time. She was scared
Speaker 1: about how her parents and community would react, and preemptively
Speaker 1: she made the claim that she had been assaulted by
Speaker 1: a group of three men and raped by one of them,
Speaker 1: and she just made it up entirely. Uh. She was
Speaker 1: brought in to the police station to talk to police
Speaker 1: officers who wanted to get a sketch artist there to
Speaker 1: get a sketch of her, her presumed attacker, and so
Speaker 1: she started making up a description. The description she made
Speaker 1: up happened to kind of resemble someone who was in
Speaker 1: a collection of mug shots at that police station, and
Speaker 1: it was a guy named Gary Dotson who had run
Speaker 1: a follow the law previously, but she had made this
Speaker 1: whole story up. It's just so happened that the person
Speaker 1: that she was describing happened to look like this guy now.
Speaker 1: According to Crowell, the police pressured her into identifying Dotson
Speaker 1: as her rapist, and she was still scared of telling
Speaker 1: the truth to anyone, so she went along with it.
Speaker 1: Dotson would end up being tried and convicted of rape
Speaker 1: and sent to prison, and Krowell would later recant her accusation.
Speaker 1: In five she said she was overcome with guilt about
Speaker 1: what she had done to him and that she had
Speaker 1: decided that it was enough was enough, she had to
Speaker 1: come forward and tell the truth. And prosecutors weren't too
Speaker 1: eager to do that. They I guess partly were worried
Speaker 1: that it was going to reflect really poorly on them.
Speaker 1: The trial had included testimony from various forensics experts, and
Speaker 1: it would mean that they were either fabricating evidence or
Speaker 1: very much misidentifying things, and that it was going to
Speaker 1: look terrible to them. So anyway, a judge ended up
Speaker 1: releasing Dotson on a one hundred thousand dollar bond, but
Speaker 1: Dotson wasn't truly exonerated until DNA tests in nineteen nine
Speaker 1: proved that he wasn't involved. So, in other words, his
Speaker 1: accuser had come back up and said, I made it
Speaker 1: all up. He didn't do anything to me. I was scared,
Speaker 1: and I came up with this story that I thought
Speaker 1: was going to help things. I did not intend for
Speaker 1: this to happen. And some of the legal community dismissed
Speaker 1: her statement. They said, oh, she's unstable, she's you can't
Speaker 1: rely upon her statements. And it wasn't until the DNA
Speaker 1: evidence came out that said Dodson could not have been
Speaker 1: the person that was accused of this crime because his
Speaker 1: DNA did not match the DNA that was gathered in
Speaker 1: the wake of her accusation. The whole story, by the way,
Speaker 1: goes into way more crazy detail and and there are
Speaker 1: a lot more twists and turns and a lot of
Speaker 1: tragedy involved in it as well. It's sad, it's an
Speaker 1: infuriating story. There's an excellent treatment of the story over
Speaker 1: at Northwestern University's Prints Care School of Law website. It
Speaker 1: has the title first DNA Exoneration. So if you want
Speaker 1: to read all about it, and it is an exhaustive account, uh,
Speaker 1: you should check that out, because it is fascinating as
Speaker 1: well as upsetting. The emergence of DNA led to the
Speaker 1: development of quality control guidelines for DNA labs and forensic investigators.
Speaker 1: It became clear that in order to make effective use
Speaker 1: of this information, of this knowledge of DNA, they had
Speaker 1: to make sure they created very straightforward, very uh standardized
Speaker 1: approaches to to reduce the possibility of destroying or altering evidence,
Speaker 1: either by accident or on purpose. You know, do something
Speaker 1: where you can document it step by step by steps
Speaker 1: so people can make certain that you did everything correctly,
Speaker 1: so that your conclusions can be seen as valid. Now,
Speaker 1: while these sciences, sciences and processes were developing, police forces
Speaker 1: and other law enforcement agencies were actually working to formalize
Speaker 1: the development and deployment of investigations. How do you teach
Speaker 1: investigators these these processes, Because a lot of them were
Speaker 1: developed independently, they are being made use in specific police forces,
Speaker 1: but they weren't necessarily shared. How did that come about? Well,
Speaker 1: in the nineteenth century, if you were in the eighteen
Speaker 1: hundreds and you were a forensic researcher, you were connected
Speaker 1: to some sort of law enforcement group, whether private or public.
Speaker 1: You were a auntly self taught. You got hold of
Speaker 1: whatever information you could find and you would study it
Speaker 1: or you would develop your own ideas in your own processes.
Speaker 1: It was very informal. One of the earliest formal schools
Speaker 1: in forensics was created by a guy named Rudolph Archibald Rice.
Speaker 1: He was a professor at the University of a Lausan, Switzerland.
Speaker 1: He had studied chemistry. At that university, he earned a
Speaker 1: doctorate in the field, and he began turning his scientific
Speaker 1: mind towards criminal investigation. He studied the discoveries of other criminologists,
Speaker 1: and in nineteen o nine he founded the Institute of
Speaker 1: Scientific Police. Other universities in Europe began to found their
Speaker 1: own forensic studies curricula, but then you had World War
Speaker 1: One and World War Two, and that wiped out a
Speaker 1: lot of those efforts. The Institute of Scientific Police survived
Speaker 1: the two World Wars because Switzerland was neutral in both
Speaker 1: of those. Today this school has a different name. It's
Speaker 1: called the School of Criminal Sciences. The same organization, new name,
Speaker 1: I mean, obviously updated with the more modern approaches. Rice
Speaker 1: in his time would actually publish a book about investigative
Speaker 1: techniques used in the event of burglaries and homicides, and
Speaker 1: he had planned future volumes to cover other types of
Speaker 1: crimes like counterfeiting, as well as other police matters like
Speaker 1: organizing a police force, but he ended up putting all
Speaker 1: of that on hold. The Serbian government requested his assistance
Speaker 1: to investigate war crimes committed by the armies of Austria
Speaker 1: Hungary during the Serbian War, and so he never finished
Speaker 1: those books. In An American named August Volmer, who was
Speaker 1: chief of police in Los Angeles, California, founded the first
Speaker 1: American police crime laboratory, which actually predated the FBI's crime
Speaker 1: lab by eight years. The FBI was formed in nineteen
Speaker 1: o eight, but it would not have its own crime
Speaker 1: lab till nineteen thirty two. It was the early nineteen
Speaker 1: thirties when colleges and universities began offering degrees in police
Speaker 1: sciences and minalistics, and in nineteen fifty the University of
Speaker 1: California at Berkeley created an early department of Criminology over
Speaker 1: in Chicago. Around that same time, academics founded the American
Speaker 1: Academy of Forensic Science, and today there are numerous colleges
Speaker 1: that offer coursework and forensic science. There are labs dedicated
Speaker 1: to the purpose of applying the scientific method when it
Speaker 1: comes to the investigation of crime, and there are companies
Speaker 1: that produce technology with the primary purpose of aiding in
Speaker 1: criminal investigations. And in our next episode, I will take
Speaker 1: a closer look at some of those actual technologies, some
Speaker 1: really cool ones, though they may not be exactly the
Speaker 1: same as what we see in television and film. That's
Speaker 1: it for this episode. If you guys have suggestions for
Speaker 1: future episodes of tech Stuff, maybe it's a technology, maybe
Speaker 1: it's a person or a company you want me to cover,
Speaker 1: send me a message emails great. The email address you
Speaker 1: can use as tech stuff at how stuff works dot com.
Speaker 1: You can drop me a line on Twitter or Facebook
Speaker 1: handle for both of those is tech Stuff hs W.
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