DNA Forensics

Ben Bowlin of Stuff They Don't Want You to Know joins the show to talk about DNA forensics, cold cases and science. How reliable is DNA evidence?

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Episode Transcript

Speaker 1 (00:04):
Get in with technology with tech stuff from stuff Peter
are welcome to tech Stuff. I'm Jonathan Strickland and joining
me in the studio today is the illustrious and Mr
Ben Bowland of stuff they don't want you to know
and car stuff, among other things. Welcome back to the show. Ben, Hey, Jonathan,

(00:24):
thank you for having me. Oh man, illustrious? Is it
the pain meds from my recent doctor visit? Or am
I'm moving up in the world. It's literally that you're illustrated. Actually,
there's true. Ben has had people mark all over him
and crayon today. I'm not gonna ask why I don't
get into personal lives in the show. Well, you know,
it's it's a big deal. Whenever I could be on
the show and I wanted to do something special, my

(00:47):
suits at the cleaners got a bunch of Sharpie's and
ask people to go nuts. Yeah, it's kind of like
body paint, but really they'll super like on the cheap
because we just can't. We don't have that in our budget, honestly,
right note, but hope springs eternal. What's weird about having
um all these all these colors and markers all over me?
Is that anything I touched literally is leaving a trace? Yeah,

(01:10):
and that kind of you know, we were going to
have a really in depth conversation on how catalytic converters work,
but once I noticed you doing that, I thought, why
don't we talk about DNA forensics, like the traces people
leave behind. So, uh, that's why I decided to switch
in the last minute. I hope you can roll with it.
Oh yeah, yeah, and just in in you know, Ben

(01:33):
and I have talked a little bit about our our
mutual interest in the true crime uh discipline, the whole
the whole true crime like field, and it turns out
we're not the only ones in the office. There are
certain people in the office who have a really deep
interest in this sort of stuff, and so we thought,
you know, would be kind of fun to explore the
concept in different shows. So if you listen to all

(01:55):
of How Stuff Work shows, you may have noticed things
popping up here and there that's not entirely by accident.
So uh really was one of those things where as
we all started talking, we're like, hey, you know, I
would like to do something in that and we can
kind of It's almost like an easter egg for those
of you who subscribe to lots of different shows, and
you should let us know if you thought it was
really cool. So from the technology standpoint, we thought DNA

(02:19):
forensics would be really really interesting to cover and to
talk about how it actually works. Uh, what are the processes,
what are some of the challenges, What are some of
the things that people are doing with DNA forensics now
that might end up helping, uh, like investigations in the future.
Where could it actually end up giving us a false positive,

(02:40):
because there there is the possibility of that as well.
But to start it all off, we really kind of
have to lay the groundwork. Yeah, I was gonna I
was just gonna ask you. I hate to be the
bad kid in class right now, but what's what's DNA?
D oxy ribonucleic acid, man, Yeah, that's what is so obviously,

(03:01):
you know, anyone who's had science class, like a biology
class anything recently, you know all about DNA. But you know,
we gotta build from the ground up. So DNA is
a molecule that carries the genetic instructions that govern the development, function,
and reproduction of organisms. DNA is found in all of
your cells. Essentially an entire blueprint of what makes you

(03:22):
you is in every single one of your cells in
the form of d N a uh, and the molecule
is in that double helix form. So that says, if
you were to make a ladder and then twisted into
a twisty shape, that's the DNA double helix. The rungs
in that letter are made up of pairs of what
we call nucleotides. Alright, So each rung on the ladder

(03:45):
is two different nucleotides that that bond together. Uh. There's
adenine and thymine. Those always pair up together. So those
are your two base pairs of nucleotides that will always join.
And then there's guanine and cytosine and those always join.
And it's the sequence of these pairs that end up

(04:06):
determining what makes you you, right, yeah, yeah, so it
could be. And these pairs can affect multiple the order
of these pairs can affect multiple characteristics. Sure, yeah, absolutely.
And also what's really interesting to me is that point
nine of all the DNA that is in you is

(04:29):
shared with every other human Like we we have ninety
nine percent of our DNA is in common, which means
the stuff that makes you who you are as indifferent
from every other person, makes up just point one percent
of your DNA. But that's all it takes, is that
point one percent. That's about three million base pairs that
are unique to you unless you have an identical sibling.

(04:53):
Ah ah the old Now this goes into um, this
verges into some good detective fiction. Now, yes, that old trope,
the evil twin, Yeah, exactly, it wasn't me. It was
my evil twin or or evil triplet or evil quadruplet
really which we did an ill fated brain stuff but
it was, oh my gosh, we did. We did. Yeah.

(05:13):
If you if you watch brain Stuff, the video series,
and you look up how twins work, Ben and I
did a funny At the time, I thought. I still
thought there were parts of it that were funny. Honestly, Ben,
I still fully enjoy it, but my sense of humor
is very corny. So but if you want to see,

(05:34):
if you want to see me and Ben dressing up
in two different types of outfits, like we're the good
Ben and Jonathan and then there's the evil Ben and
Jonathan and we each have an eye patch. Jonathan and
I were talking and it was it was strange because
when we were talking about doing this episode, we said, wow,
how could we represent evil twins like I I patches?

(05:55):
Clearly because you know, the goatee is not gonna work
for right because and like neither of us were going
to end up shaving just so that I can be
the good twin. But both of us are the kind
of person who would have an I patch. And actually
I ended up taking a quick walk to a nearby
toy store to pick some up. Um. So, at any rate,
if you do have an identical sibling, your identical sibling

(06:16):
shares your DNA. There they are identical, like the DNA.
If you were to compare the two and look at
those base pairs, they're going to be the same all
the way down, right. So that's one of the that's
one of the exceptions, really the exception. So our DNA
can be found in twenty three pairs of chromosomes. That's
what humans have. Not all animals have that many, so

(06:39):
have fewer and etcetera, etcetera. So chromosomes are ribbons of
protein essentially have a strand of DNA that are wrapped
up in that and within each pair, one chromosome comes
from your mother. One chromosome comes from your father, and
that's what uh you know, those are the ingredients that
come together to create the unique individual that is you

(07:00):
and or your identical siblings. Uh So, if we took
look at each person's DNA and pay attention to the
order of those base pairs, we get something like a
DNA fingerprint. It is unique to that person. But we
can't just look at one section. We have to look
at several different sections also known as loci in the
in the parlance of forensics to get a robust fingerprint profile. So,

(07:24):
just as we would look at a fingerprint and look
for points of comparison to from from a from a
fingerprint that we've gathered from a suspect, let's say, and
a fingerprint that was left at the scene of a crime,
you would have to look at several different points to
make sure that all those points correspond to one another
to say that there's a match. Same thing with DNA
DNA forensics, you would look at several different locations along

(07:47):
a strand of DNA and see if the same sequence
of nucleotides were appearing on both sets, because that would
tell you what are the statistical probabilities of the person
that you suspect and the the evidence that was left
behind are one and the same, right, Okay, So each

(08:08):
time there's a new location, the more loci there are,
the more certitude you have that you've got your catch. Yeah,
if you were to say, look at just one location,
then that would mean you would have a very you know,
there's actually quite a good chance, depending upon the sequence,
that coincidence could could completely explain away any any uh

(08:31):
duplication there. Right, So it could just be coincidence. It
could be that this person just coincidentally has that same sequence.
As you add more loci, that becomes less and less likely.
Uh FBI. The FBI has thirteen that they suggest the
thirteen specific loca that's their standard, and that that results

(08:53):
in about a one in a billion chance that if
you were to take all thirteen loca and compare the
two strength you know, the stuff that was left at
the evidence and the suspect or whatever is in the database.
If you were to compare the two and they were
to come up equal at all thirteen, it's a one
in a billion chance that somebody else besides the person

(09:15):
you're looking at, possesses that. So seven of the six
other people in the world. Yeah, it's like flash forward
to that day in court where someone's doing that horrible
reference joke and going, so you're saying that there's a chance. Yeah,
And and honestly, people who are analyzing the stuff, they
speak in statistical probabilities, because you cannot say for certain

(09:39):
that this person left behind that DNA. You can say, like,
what is the statistical probability that they did, And then
you look at other elements of the case, right, like saying,
all right, can we put the person in that area,
because let's say that it's in a small town. Well,
if it's a one in a billion chance and you
know that the suspect was in that small town, that's

(10:01):
pretty darn compelling. Yeah, because why are the chances that
the other one of the other six people in the
entire world was also in that small town? Not good?
So where do we get the DNA evidence from? Well,
stuff that people leave behind, Uh, pretty much anything that
has cells like living tissue that was left behind our

(10:23):
living or stuff where living cells could have been in
before being deposited at the crime scene. So stuff like
blood or saliva or semen or skin cells, mucus, earwax, sweat. Yeah,
all of that, All of that can leave behind cells
that we can pull DNA from that. What about hair,

(10:45):
hair not so much, not not not for traditional DNA
hair follicles, Yes, but hair it self is dead. Those
are dead cells. So you can do some some DNA analysis,
but not the standard kind that most people use in DNA.
For instance, Uh, fingernails, same thing, but fingernails often come

(11:06):
with other tissue attached to it, and that's where you
find the DNA. So if we want to look at
the history of people actually saying, hey, why don't we
use this this DNA stuff to try and help with investigations,
you've got to look back to the nineteen eighties when
a brit named Alec Jeffries, who now you may refer

(11:28):
to as Professor Sir Alec John Jeffreys f R s okay, good,
Professor Sir Alec John Jeffries, FRSH that would be his
full title. Now, he hit upon the idea of using
DNA as a means of genetic fingerprinting, and he realized
that the unique sequences of DNA could serve as a

(11:49):
means to link an individual to a scene where DNA
samples were found, and his process was first applied in
the court system in nineteen eight five. In that case,
it was an It was an immigration case. It wasn't
like a murder or a rape or something like that.
It was to ascertain if the identity of a British
boy was actually related to a family who had originally

(12:11):
immigrated to the United Kingdom from elsewhere. And he did. Uh.
The first time it was used in a criminal case
would be seven. That was yeah, not not long after,
and that wasn't a case. Uh. The the suspect was
named Colin Pitchfork, which is a heck of a name,
talking about nominative determinism. Yeah, and he was arrested on

(12:34):
suspicion of rape and murder. And he was the first
criminal caught as a result of DNA screening. So this
was DNA screen that led to his capture. He actually
confessed to his crimes, so the DNA didn't lead to
his conviction. He confessed, uh, and he received life in
prison as a result. So I wanted to talk a
little bit before we get into some of the pros

(12:55):
and cons about what actually happens with DNA's because you
hear or like DNA forensics and you're like what goes
into that. Yeah, this is a great thing to contextualize
right now, because there are a lot of fans and
tech stuff who have probably seen and scoffed at the
various entertaining but inaccurate crime shows on order spe CSI,

(13:21):
CSI being the big one, like they're there are are
forensic specialists who say that c s I is probably
one of the most damaging things that have happened to
their their career path ever, because people have unrealistic expectations. Specifically,
juries have unrealistic expectations, which can hurt a trial case
because juries will often one want DNA UH data when

(13:44):
it's not even relevant to a case, Like they're like,
it's not necessary for them to make a determination in
a case, but they want it because it's one of
those things that people associate with. Oh, d NA gets
you the the locked in answer was that person air?
Were they not there? Um, just run the DNA enhance
the photograph. I don't see what the problem right exactly. Yeah,

(14:07):
let's pull up one of those three dimensional holographic images
and we're just we're just throw every single science fiction
CSI trope in there. So early forensic analysis actually used
a process called restriction fragment length polymorphism or r f LP,
and that involves taking a sample of DNA that has

(14:29):
repeating base pairs like they can repeat from anywhere between
one and thirty times. They're called variable number tandem repeats
or v N t r s. And what they would
do is they would dissolve this DNA in an enzyme
to break the strand at specific locations along that the DNA.
So uh saying like um, when there are this many repetitions,

(14:52):
this enzyme is going to break the strand at that point.
So that way we can measure how long the strand
DNA is in a out point. Yeah. So imagine that
you've got like a ribbon, right, and let's say that
the ribbon is maybe three ft long, and you're going
to cut out a six inch segment of that ribbon.

(15:13):
Use this enzyme and it cuts it at the very
specific locations along that strand that you want. You do
the same thing with the material that was left behind
at the scene. So let's say you've got you've got
your your DNA sample from your suspect, you've got the
sample from the scene, and you compare the two and
you're essentially measuring them against each other, like literally measuring

(15:37):
the length of them, because it's those repeating pairs that
determine how long that segment is. So if the two
are about the same length, or actually they are the
same length, then you know, or at least you you
have a good uh inclination to say that this person
was the one who left behind that DNA. That's not

(15:59):
really used that frequently anymore, but more frequently now we
use a method called short tandem repeat analysis, which is
more reliable, more popular. And in this method, analysts take
a sample of DNA and they count the repetition of
those base pairs along certain locations the loci of that sample.
So four or five base pair repeats like where you

(16:20):
get you know, your your those nucleo tide pairings I
talked about, Sometimes those pairings repeat in a sequence, right,
They look for uh, preferably four or five base pair
repeat segments, so that way, because it's less likely than
if you would have two or three in a row. Yeah,
the more you have in a row, the less likely

(16:42):
you're going to find that exact same repetition in another
in an unrelated person's DNA. And these are by the
way called tetra nucleotide or penta nucleotide repetitions because of
the number tetra being four, penta being five. Um. There
those are best in order to indicate an accurate man match.
So the FBI, like I said, says, thirteen specific locai

(17:03):
to find this, you would do this in thirteen different
locations along the strand of DNA. And if you were
to find these, uh, these base pair repeats that are
identical in both and both samples, that's a really good
indication that they belong to the same person. And this
this investigation technique, while it is, while it's pretty solid

(17:26):
and there's solid science behind it, it doesn't work in
every In every case, it's not a silver bullet. And
this is kind of some dark territory. Yeah. Yeah. In fact,
there there are a lot of reasons why, uh, this
can be this can be problematic. Um. One other thing
I want to talk about before we get into the

(17:47):
challenges specifically things like contamination and chain of possession and
chain of custody, thank you, Before we get into that,
is to talk about all right, so you know, I
gave these these overviews of how they're analyzing the DNA,
but One of the big issues here is that often
when you're in the field and you're looking for anything

(18:09):
that has, you know, remnants of DNA on it, you
may not have a very large sample to work with. Right,
So you've got a tiny amount of DNA. How do
you make sure you can do the tests you need
with a tiny little amount? And the answer is you
duplicate the crap out of it? What how? Yeah? Okay,

(18:30):
so this is this is gonna get super weird because
I'm gonna get into molecular biology and chemistry but starting
and I want to let okay, So they use a
process called polymerase chain reaction or PCR to duplicate a
specific region of the DNA in a sample. So this
process was developed in three by Carrie Mollis who actually
he won a Nobel Prize in chemistry for his work

(18:52):
in this field. And what they'll do is they'll take
samples of DNA. They'll take a string of DNA, so
you've got your double helix, right, and then you heat
it to between ninety four and ninety six degrees celsius
for a few minutes. Yeah, so it's almost boiling um
for a few minutes. And this is to d nature

(19:14):
the sample, which means that the DNA straightens out, so
it's no longer twisted ladder. It's a ladder, and the
rungs split apart, So those base pairs split and you
get two strands two half strands of d N A alright,
So then you end up changing the temperature. You lower
it to between fifty and sixty five degrees celsius for

(19:36):
a few minutes, so that first one only takes a
few minutes to so you lower it down to fifty
to six degrees celsius for a few more minutes. That
allows the left and right primers. These are small sections
of DNA that have matching nucleotides to the two separated
pieces that you've created. Think of them as almost like
half zippers. So you've got the right and left half

(19:59):
of a zipper on either like that. They're spreading out
there there there's apart from one another. You've got a
small section that interlocks with each side. Because that you've
got the the complementary base pairs. Uh, those will then
connect to those sections. Now that's only a tiny little

(20:19):
part overall part of the full DNA, but um they
then raise the temperature to seventy two degrees celsius for
a few minutes to allow the tach polyme race. Now,
this is the material that can then build and synthesize
new DNA to the two separate strands. So if you
think about it like a video game. All right, so

(20:41):
you get your little you get your little segment that's
locked onto the half ladder of DNA, the stuff you
started off with in the first place. At one end
of that, imagine that you get a little bitty blob,
all right, that little big blob just builds the corresponding
rungs and goes down the line rebuilding the d N
A and it doesn't you know, there's one on both sides.

(21:03):
There's a primer on each half strand of DNA. So
at the end of this process, you end up with
two strands of DNA. Okay, I see, now you started
with one, but because you've used this molecular biology slash
chemistry approach, you've been able to duplicate it. And then
you repeat that process. So you do it again. Those
two become four, the four become a. You see how

(21:26):
this expands very rapidly. You do it over and over,
so that way even if you started with a very
small sample of DNA, by the end, you've got plenty
to work with, so you don't have to worry about
you know, we had one little drop of sweat at
the scene and and we blew it on on a
test that didn't work out. You don't have to worry
about that. I'm sorry to be like, uh, emotionally or

(21:48):
mentally a nine year old here, Jonathan, but can we
can we make it a booker? I just love picturing
us as cops or like, no, no one knows who
stole the vus. We have only this single. The Mysterious
Picker has struck again. Yeah, yeah, okay, so you're in Yeah,
well we weren't talking about urine. We were talking about
the boogers. All right, you got me. But this is

(22:11):
but this is a great that that's a great explanation
of how this occurs. Because given that you're essentially destroying
the evidence every time that you you conduct this kind
of this this kind of investigation, than being able to
reproduce it is fundamental. Yeah, it's absolutely key because again,

(22:33):
if you do not have very much of that material,
then you really have to be careful. And there are
a lot of things that can complicate this, and that's
kind of where we were leading to a little bit earlier.
There are a lot of reasons why you cannot just
say that DNA forensics is going to solve, you know,
the crimes out there as long as someone's left something behind.

(22:55):
Because even though it's versatile, even though we have this
amazing capability, life is weird and things can go wrong,
and they can go wrong either accidentally or on purpose.
So one thing that can happen is multiple people could
be involved in a an incident crime of some sort,
and so the more people who are involved, the harder

(23:16):
it is to be absolutely certain that the DNA samples
you're working with all linked to a specific individual. In fact,
there are currently some changes in the way DNA can
be handled UH in cases court cases actually to the
point where it's in the legal case since UH in
Texas and other places as well, and so forensics labs

(23:40):
are having to put in greater restrictions because forensics analysts
would go into testify in court cases and say there's
a one in a billion chance this belonged to someone else.
But if you start to factor in that there is
more than one person's DNA found at the scene and
the contamination issues that result from that. Then people would
say like, all right, well, really it's more like one

(24:02):
in a thousand or one in a hundred. And then
at this point you might say, well, the DNA evidence
is not strong enough for it to be a compelling
argument for the guilt or innocence of a person, because
there's enough like if you're in a really dense urban
area and you say there's a one in a hundred
chance that's you know, it's it's hard to say that

(24:25):
shouldn't introduce reasonable doubt that it doesn't meet the burden
of reasonable doubts, But and then you have to try
to chase down all the other possibilities. And that's that's
if there are multiple people involved. But even if there's
not multiple people involved, obviously you have to be very
cognizant of the possibility of contamination. Yeah, okay, we we

(24:49):
can talk about this a little bit because we this
is something that you might not see on Hollywood as
often as you see it in real life. Yes, actually, Jonathan,
so let's say you know the let's say you're the detective,
right and Noel is the prosecutor, and I'm the I'm

(25:13):
the JABRONI at the scene. You was supposed to pick
up the stuff and bring it, right Yeah, So you're
you're your job is to actually go in and collect
the evidence before anyone else can go through that area,
right yeah, because as soon as you introduce other people,
then you've introduced other DNA that could be left at
the scene. But I've been having a I've been having
a crazy time work lately, and I've been cutting corners

(25:36):
a little and everybody knows. Nobody said anything yet because
it's not a big deal yet. But here's what happens. Uh,
while I'm on while I collect the evidence, let's see,
I get blood samples, and I'm on the way back,
I stop it cook out because my diet is as
much of a train wreck as my life and I'm

(25:56):
not and because i'm personally I shake hands with six
people as I'm walking back into our building. I don't
wash my hands. And I also kept the sample for
some reason in the bag from cookout. Yeah, that would
there there might be a chance that that was encountered
some form of contamination from the scene to the point

(26:19):
where you get to the lab and then you you
run the d NA. Yeah, right, Well, clearly the suspect
was a roast pig, right, Yeah, clearly suspect was a
roast pig. Or even more dangerously, clearly the suspect, uh,
the suspect maybe someone that already pings in our database
who just got out of prison for grand theft auto

(26:40):
and now works out of cookout. Yeah. Yeah, that's I
mean that that's a you know, it's it seems like
it's a convoluted example except for the fact that this
is the sort of stuff that can happen r Yeah,
it's not. I would say it's possible, but that one
is not plausible. No, no, But but the example you
give does show that there has to be great care
are the the people who come in to collect the

(27:03):
evidence have to do so before there can be a
lot of disturbance of the crime scene. Because the more
disturbance there there is, like I said, the more chances
other people will leave behind DNA skin cells or or
um sweat or blood or whatever it might be. Um
might be that there were other people who were involved
in it who have no or you know, people who

(27:24):
maybe the person who stumbled upon the scene left something
behind without intending to like cutting a hand on a
on a piece of glass or something, letting themselves into
see what's happened. Yeah, even something as simple as that.
So there's there's that you have to be aware of
contamination there. You also have to be aware of contamination

(27:44):
through the moment you've collected it, all the way through
the testing phase. So that's where the chain of custody
comes in. By the way, if you ever see people
like putting stuff in plastic bags in order to preserve it,
that's pretty much a fiction because play stick will will
contain moisture, right anything, Any moisture that's in the bag

(28:05):
will stay there, and moisture can can degrade DNA samples.
So usually they're actually put in paper, so it's usually
a paper envelope or a paper bag that's quickly labeled.
And then there's this chain of custody that must be
documented through the entire process until it gets to the lab,
and then at the lab. Even at the lab, they

(28:26):
have to be very careful with the equipment they're using.
They have to make certain that it's completely clean. That
way you don't end up cross contaminating from a previous
test into your current test. That's happened a couple of times.
There actually been a couple of cases. Yeah, there was
a case where, uh, there was a victim of a
crime and there was another crime that was committed, and

(28:49):
the initial DNA test results of the crime that was
committed came back with the victim from the other crime
as a positive. And they realized that the reason why
that was happening was that there were two different DNA
tests that had been performed, and the victim from the
first one that their DNA had not been completely cleaned
out of the system before they started doing the next test,

(29:11):
and so they were getting these false positives, and they
knew it couldn't have been the victim because the victim
was the victim was victimized, the victim was not capable
of committing that crime. Um, so it was already like
one of those things that proved that there was an
issue here. And in almost every case, in fact, I'll
go ahead and say the vast majority of cases, this

(29:31):
has to do with a person either mistakenly or purposefully
not following procedure or not making certain that that everything
is on the up and up. Rather than the process
itself being a failure, it's it's a human error, either
intentional or otherwise introduced typically um and so another thing

(29:55):
that you have to worry about is whether or not
someone has purposefully introduced DNA. There have been cases where
in order to try and either uh to hide one's
involvement in a crime or to implicate someone else specifically
in a crime, people have left behind samples of DNA

(30:18):
in order to throw people, throw investigators off the track.
Whether again, whether it is to protect yourself, Like let's
say that you committed the crime, and you leave behind
the DNA of you know, your your your hated cousin,
so that your cousin takes the rapid you don't, or
you're an investigator and you're like, well, there's this really

(30:39):
awful guy, and we want to get him for this crime.
We really like him for this crime, but we don't
have the direct evidence for him. However, I do have
this DNA from a separate incident. I can leave this
behind the crime scene collected, and therefore we can finally
get the guy. I'm pretty sure he did it anyway,
you know, solid solid stick, Steve four percent sure. So

(31:02):
that's again, this is not something that happens all the time.
It's not not something that's even prevalent, but it's it's
one of those things that you have to be aware of.
That's why these things like the chain of custody is
so important to maintain. I have a question, sure, uh,
and I don't know if I'm jumping ahead here, please ask.
But I was kind of foreshadowing this when we're asking

(31:23):
about hair follicles. So the it sounds like the home
run for h for DNA testing would be something, as
you said, containing living cells, so blood, bodily fluid, stuff
like that. But if that's a home run, the kind
of stuff that people are much more likely to leave

(31:44):
behind would be things like hair follicles or flakes of skin.
You know, So, what what's the deal with that? How?
How does that work? It's still the same same process
in the sense that these are things that can leave
behind traces of DNA like as long as as long
as they For instance, let's say that you have you're

(32:07):
at a murder scene scene and you are you are investigating.
One of the things you're going to look for are
traces of any skin under the victim's fingernails, because that
that's a an indication that the victim fought back against
his or her murderer and may in fact have samples
of that skin underneath his or her fingernails, And so

(32:30):
you can collect that and then do the same process
I was talking about. You can extract the DNA from
those cells and then do the same process to duplicate
that DNA and then run it either against suspects DNA
or or use a database. We mentioned the databases briefly
a little bit about Yeah, let's do that, because there
are a couple of different ones. There. There are state databases,

(32:52):
there's a national database, and then there's the FBI's database.
Uh So these are all databases that continue in the
DNA information of various people who have been booked for
specific types of crimes. It's not every crime. Don't worry,
the FBI does not have your genetic blueprint because one
time you purposely parked in a handicap spot. Although Jonathan

(33:16):
and Nolan I do judge you for that, Yes, we
think you should definitely never do that. If you don't,
if you do not have a the handicap label, uh,
then don't park in that spot. But now these are
specifically pretty serious crimes where that's really the only way
that they that that the state or federal government is

(33:38):
allowed to to collect a DNA sample from you to
use in this database. When they've got a lot of people,
I've got some statistics here to yeah, please hit me. Okay,
So let's let's go with the big one, right, Okay,
The big one here in the States is the National
DNA Index or in d I S. That's the that's

(34:00):
the feed's that's the FBI. It contains a little under
twelve million offender profiles, specifically eleven million, eight hundred nine
hundred and twenty seven. It has to a little over
two million R s D profiles and a little over
six hundred thousand forensic profiles. That's as of June. If

(34:22):
you visit the FBI's website, you can learn a lot
about their biometric analysis, which does also contain print work.
It's it's sort of a mixtape of all the stuff
that they could use to investigate. And here's the thing
you can do if you live in the US and
you would like to feel a little bit less comfortable
each day, Okay, it's there's a breakdown by state, so

(34:45):
you can see how many offender profiles are are located
in your state. Here in Georgia. In our case, it's
two hundred nine thousand, nine hundred and thirty eight. Considering
the population of Georgia, that is a significant number. Right,
you can see the forensics profiles the arrestees. You can

(35:06):
also see the number of investigations aided in labs participated. Now,
one of the things I want to point out is
that this also goes back into the drawbacks or the
challenges of forensics, is that forensic labs can get really
backed up with this stuff, Like the backlogs can be
can be crazy because while I I you know, I

(35:29):
mentioned that process just for duplicating the DNA, that can
take a couple of hours to do that process, and
then of course you've got all the cleaning of the
material that has to happen in order for you to
be able to use it again. That's not that doesn't
even involve the actual analysis of the DNA that tends
to require a forensic specialist to do this. It's not

(35:52):
like it's all automated, although there are more and more
automated systems that help, but generally speaking, it's it's sort
of an augmented approach where you still have a forensic
expert do the the look you know they're doing. They're
looking at the DNA to look at those base pairs
and actually makes certain visually that they are in fact identical.

(36:16):
So it takes a lot of time. And meanwhile, while
you're doing all this, more samples are coming in. So
there's a backlog that starts to build up, and depending
upon the area and the number of labs that are available,
it might be a very serious backlog. And there was
also a pre existing backlog because if we look at
how recently this occurred, and off air we talked about this.

(36:40):
In the course of your research, you send in some
great stuff about cold cases. Yeah, so there was already
a built in backlog for this technology, and they're already
been cases of people who were in jail for years, decades, Yeah,
who were innocent. Yeah, yeah, where the DNA evidence ended
up clear daring them like it could not possibly have

(37:01):
been that person. Um. And you know, actually, that's when
I say that there are some serious restrictions in tax
us about this multi person DNA approach. It's specifically so
that there is every attempt to make certain that innocent
people aren't incarcerated there is a huge obviously, there's a

(37:23):
huge pressure on law enforcement to to assign guilt and
uh and bring somebody in for particularly awful crimes. And
there's an enormous pressure because of course, the community wants
to feel safe, they want to feel that something is
being done that has to be balanced against making sure
you get the right person. Yeah. Yeah, because we know

(37:46):
that we live in an age of instant gratification. Yeah,
things should be right immediately and right the first time,
and right now and right now. Yes, the three rights.
But unfortunately, the wheels of justice. How's the old saying,
go man? They grind slow but exceedingly fine, Yes, as

(38:06):
opposed to go round and round. Yes, the wheels in
the bus. I was thinking, you know, we would be here,
terrible lawyers. Yeah, we would be Actually, I know I
would be. I remember participating in a mock trial in
school and not knowing what the heck I was doing?
What was your what was your rule? I was defense
and it was terrible. It was terrible. I did not

(38:27):
want to do it. I was I was. I was
bullied into it and I it was awful. I can
see you doing like a judge or maybe a bailiff,
who's over it, like, sit down? Yeah, no, I was.
Uh my my client would have gotten the chair. It
was terrible for a very minor offense too, That's how

(38:47):
bad I was. So anyway, getting back into DNA forensics,
Uh so, yeah, you mentioned cold cases, I've got one
specific one I'll mention, and it's not it's one that
has not been um scene to completion yet. In other words,
there there hasn't been a conviction yet in this case.
But it does show how how far reaching this can go.

(39:08):
So in December, the body of a young lady named
Crystal Lynn bez bes lana Wich was found along the
Provo River in Utah. She was seventeen years old when
she was killed, and she had been sexually assaulted and murdered. Uh,
perhaps bludgeoned to death with rocks. That was what the

(39:31):
police believed at the time. Now, the original investigator of
the crime, it was a guy who became the the
deputy sheriff, I believe, but Todd Bonner decided to continue
investigation even long after all the leads were drying up,
like they just could not find any leads. Uh, and
in a lab was able to extract what's called touch

(39:53):
d n A. It was left behind on a granite
rock that the police had believed was used in killing
this young lady. And the lab used a vacuum instrument
to pull this touch DNA off the granite rock and
then put it through this analysis process and the results

(40:14):
ended up matching DNA from a suspect that people were
interested in but had no direct connection to the crime.
The suspect's name was Joseph Michael Simpson, and they got
the sample DNA from a discarded cigarette butt he had
tossed aside a cigarette but the cops scooped it up,

(40:35):
they tested the DNA, they found a match. They arrested
him back in Uh. He has a previous conviction for murder.
He had actually been out on parole for eight months
before before Brasilanta, which is death. Yeah, so he had
been in jail for several years but got paroled and
then uh, eight months later Brisilana, which was dead, and

(40:59):
he's been linked to this and arrested for the crime.
Now that being said, the last I checked into this case,
you know, that was back in the last I checked
into this case. It's still not it still hasn't been tried.
There's been request for more evidence on the prosecution side,
including uh, an actual DNA sample from Simpson himself to

(41:24):
confirm that the findings are in fact accurate, so in
other words, not just from the cigarette, but but from
Simpson in custody. And then there's also a request to
get a print sample because of a partial print that
was left behind on the victim herself. So uh, this
case is not one that's like cut and dry and

(41:46):
it's definitive, but it does indicate that this approach is
able to start pulling up connections that otherwise would have
been unlikely or even impossible to make. And this brings
us to this is just a sidebar, Okay, this brings
us to a dangerous thing. And you know, of course
that I who can sometimes be a cartoon of myself

(42:08):
and am required to mention this. What do you think
about the idea of blanket DNA sampling? They're taking every citizen.
You know, some prominent members of the UK legal system
have advocated this for all British citizens, and Kuwait is
doing the same thing. Well, let me put it to
you this way. Okay. There's always the argument that some

(42:33):
people will make that if you're not doing anything wrong,
then what do you have to fear? Right, Well, here's
what you have to fear. I'm gonna tell you. Okay,
So there have been at least a couple of companies
that have shown that through a little bit of your DNA,
they can do a very similar process to duplicating DNA,

(42:53):
which means that they can synthesize your DNA, which means
then that if your DNA can be synthesized, it could
be cre aided and dropped somewhere. And you had never
been to that place. Oh wow, So all of a
sudden you get a summons for some horrendous crime in
uh Iceland or something. You say, I've never been Yeah,

(43:13):
this is the weirdest thing because I've never been there. Like,
but this is match to your DNA. There's a one
and a billion chance that someone else did this, um
and you you know that's that's a thing like, that's
we're in a world where technologically it is possible to
do this. Now is that likely to happen? So it's
definitely like and it's in the realm of possibility but

(43:36):
not plausibility. However, as long as it's possible, then I
would argue that it is too invasive to demand from
your population that everyone submit to d N A like
submitting a DNA sample. Yeah. Yeah, what about let's take
a step further. What about the idea that there would
be what about the idea that this stuff, which is

(44:01):
you set a blueprint in some ways. Also it's it's
similar to Metadataeah okay, let's I can see where you're saying.
So the ability then to build this enormous sample size
let's say the entire population of the UK. I think
right now they're only at maybe five of the population
because you have to get you know, you have to

(44:21):
get pinched. So if they had this enormous sample size,
then they could start comparing and collating and analyzing this
stuff on a larger scale such that they would be
able to possibly again possibly not plausibly, uh predict um,

(44:42):
not epigenetic trends, but but predict the likelihood of someone
incurring a certain disease or something. Well, we're getting into
more of a genomic sequencing at that point. Yeah, we're
getting into gatica. Yeah. Yeah, when you're when you're getting
into genomic sequencing, it's it's much further. It's it's a
much longer process because again, this is very close to

(45:04):
when they call a genetic fingerprinting. It makes sense to
call it that because you're really just looking at the
physical resemblance of two strands, right, Like like two drawings,
and there are two drawings of ladders, and if the
two drawings of ladders are the same, then you know
you've got a one and a billion chance of it
not being that person. So that's a lot different than

(45:26):
going through and identifying things like which genes do what
I mean, we still don't even know, right, So in
case you guys are not terribly familiar with with genetics,
the genes can be pretty complicated things. Think about like
a giant switchboard, right, You've got an enormous switchboard and
there's like a thousand switches on little metal toggle switches,

(45:47):
the classic updown toggle switches, right, unlabeled that you have
a bank of lightbulbs in front of you, also unlabeled.
You flip one switch and one light bulb comes on.
You flip a set can switch. That lightbulb stays on.
Three other lightbulbs come on. You turn off the first switch.
Only one lightbulb goes off, and you start thinking, Okay, wait,
what how is this real? Well, that's the thing about

(46:10):
genes is that they it's not so simple as to
say that this one gene is in charge of this
one trait. It's it can be much more complicated, where
it's a a selection of genes that some are active,
some are not active. Um. So because of that, even
if you've got all the DNA from an entire population,

(46:33):
you might be able to say, well, this one person
suffered from a particular inherited disease. Let's examine the DNA
and then compare it to other people who have suffered
from that same disease and see where the points of
comparison are. But that is, I mean, it's a monumental
task because you've just it's beyond taking thirteen points along

(46:54):
a strand and comparing the them against a second sample. Right,
It's it's a it's another it's almost like a a
an order of magnitude greater in the amount of effort
that you have to take. Yeah, that's a really good
way to put it. And that that a squatches some
of my apien predictions. I do have one other question,
all right, So we talked about in identical twins. Right there,

(47:20):
there is another there's another possibility where a person could
get pinched with the wrong DNA. Are you going with
a clone? What's your Well, there's a there's another possibility. Wait,
maybe not. It's not the same as identical twins, but
it throws another monkey wrench into this. Uh chimeras. Oh interesting? Yeah, okay,

(47:47):
Uh all right, Well I want to hear your thought
process on this, because this is not something I specifically
looked into, because chimerism is not that it's super rare. Yeah,
it's not that it's like an episode of SPU for
that time. Um, and so yeah, it's true though it
sounds crazy. And you guys talked about this on one

(48:08):
of your other shows, right yeah, and Forward Thinking we
talked about chimeras, and yeah, it was one of those
things where where the more you talked about it, the
more the more like unsure I was that I was
reflecting the reality because it seems so weird. It seems
very very strange. So it's a person composed of two
genetically distinct types of cells, So you might have Um,

(48:33):
I think the first time I was discovered it was
related to blood type, right, yeah, I believe so I
believe you're correct, So somebody had more than one blood type,
which is already so trippy to me. I just felt
like to do the to do justice to this topic,
we would have to mention that that is one of
those very very exceedingly rare cases where DNA testing is

(48:59):
not a and a silver bullet. Yeah, so you could
in a bizarre like this is almost like a science
fiction novel approach. Yeah, like to the point where you're like,
for this to work, so many things would have to
fall in line perfectly that you might as well say
it's impossible. But imagine that you have a scenario in
which you have a chimera and DNA is left behind

(49:21):
at the scene, but it's only one type of DNA somehow,
and then the sample they get is somehow just the
other type of DNA, thus exonerating your your perpetrator. Um. Practically, Yeah,
there's no, that's impossible. The only way that that could
really affect it is if there were somehow a chimera

(49:43):
on the involved in this scene and it became a
contaminating factor, because then they would say, well, aside from
the victim, it seemed it appears that there were three
people here. Yes, that that would certainly, that would certainly
cause problems, right, that would certainly cause confusion in the
whole process. But it's also so rare for someone to
be a criminal. I think it's already yeah, begging, beggaring

(50:06):
belief right right, like like like you you already have.
Like if you think of the population of people who
have some form of of that, you know, the chimera
DNA thing going on, and then within that population, what
percentage of those people are our master criminal? Yeah, are
are committing these sort of crimes. It's got to be

(50:28):
pretty pretty small number. I'm sorry, man, I'm sorry. I
just had to bring it up. No, No, it's fine, Like, yeah,
it's it's you know, but what if So one other
thing I wanted to talk about. I almost forgot about this.
So did you read up about the um the technology
of reconstructing a person's face using just DNA material, and you,

(50:54):
like you, you had sent that to me off there,
and I was initially skeptical when I was looking at it.
So it's it's called Snapshot, and it's from a company
called Parabond and Snapshot what it's what it attempts to
do is take the information from a DNA sample and
create a essentially a police sketch of a person, a

(51:16):
three dimensional uh representation of what a person might look like. Now,
when I say might look like, you've got to be
super generous with this because if all you have is
the DNA, if that's all you have, like, you don't
have any any knowledge of what the person's face looks like, otherwise,

(51:36):
how old they are, they're high, or anything. What you'll
be able to do is probably approximate their skin tone,
their ethnicity, their gender at least their biological gender, the
their hair color, their eye color, that kind of stuff,
whether or not they have freckles, that kind of thing.
But beyond that, you're not gonna be able to tell

(51:57):
their age. You're not gonna tell their high or weight,
So you can't you can't tell how heavy said or
thin they may be. How you don't know how much
how much like what sort of wrinkles would you need
to add in if they're you know, if they're older. Yeah,
you wouldn't know any of that, uh, And you wouldn't
know their skull shape, Like you wouldn't know their face shape,
right like the DNA wouldn't. So so what you can

(52:19):
do is create like a very generic looking person but
with those traits. So it may not be so useful
in the sense of using this as a means of
trying to track down the suspect. There may not come
in handy. Where it might help is if you have
unidentified remains. So let's say you've found the remains of

(52:41):
a person and you're able to extract some DNA information,
but you're not able to ascertain the identity of this
this person. Uh, this would allow you once if you
have the person's like skull, like if if that's part
of the remains that are left behind, you then know
at least the dimensions of the skull. And they're also
other technologies that allow people to approximate what a person's

(53:03):
face looks like based upon their skull shape. So combining
those two where you you say, all right, this is
what they're they probably look like based upon the the
shape of their skull. Plus here are their characteristics that
they had according to their DNA, then you might be
able to create a few different looks for that particular

(53:25):
individual that might help in identifying who that person was. Yeah,
and that that I think is the most tremendous possibility
of this technology, absolutely right, because we're seeing already that
the study of DNA and and the application of this
sort of science has fundamentally changed the nature of crime

(53:48):
and investigation. Yeah, to the point where again it can
affect juries, uh and there, and their perception of a
case to the so so it can be a frustration,
right like if you have if you have other lines
of evidence that clearly indicate that the person accused of
the crime has committed it, but because there was there

(54:10):
was no DNA evidence, or maybe there was some problem
with the chain of custody, that can create enough doubt
in a jury's mind. A jury that's been conditioned to
believe the DNA evidence is the end all be all
that it can it can cause problems in that case.
This is this is the thing is that human beings
were messy, right Like we're not just messy and that

(54:31):
we leave DNA behind. We're messy in the way we
try to process information. And so sometimes you know, when
you go through an entire process of when a crime
is committed, to figuring out who potentially did it, to
apprehending that person, to then trying that person for the crime,

(54:51):
to then deciding whether or not they're guilty. I mean,
there's so much stuff going on through that whole process that,
you know, honestly, I think we should have a whole
podcast devoted to it, you know what. I think that's
a great idea. Yeah, I mean I'm not talking about
an episode. I mean we gotta have a podcast, like
an entire show, a show specifically dedicated to this kind

(55:14):
of stuff. Yeah, you know, I completely agree, and we'd
like to hear from you if you agree as well.
You if you like this stuff, you can check out Oh, Jonathan,
I want to put you on the spot here because
as he puts you on the show, would you like
to come, uh look at some stuff like this with
Matt Nolan I over on stuff they don't want you
to know. Yeah? Absolutely, all right, certainly. Okay, Well you

(55:37):
agreed on air, so that counts. That's like a pinky problem. Here.
Here's the thing is that if you were to pull
the how Stuff Works podcasters and ask them, would you
be interested in occasionally hosting a show about crime? I
think an overwhelming majority of us would say yes. Like,

(55:57):
here's the thing. It's the quiet ones you gotta worry
about right, Scott, Benjamin crazy interested in this stuff, so interested. Yeah,
and uh, he'll be coming up on your show a
little bit later, right, Yeah, I'm gonna have him on
and we're going to talk about Volkswagen and the scandal
about Volkswagen's method of cheating emissions testing. So we're gonna

(56:20):
we're gonna go into great detail. That's gonna be in
a couple of weeks, so you guys keep an ear
out for that. But uh so it'll be crime, It'll
just be corporate crime. So Ben, thank you so much
for coming on the show. Obviously, guys, you gotta check
out stuff they don't want you to know. Check out
car stuff, check out all the videos that then works

(56:41):
on brain stuff, what the stuff. These are great shows,
and uh you know, if you are not familiar with them,
check them out because if you like this, you're gonna
love those. That's that's a guarantee. You're too kind of Johnathan.
I appreciate it immensely. I'm glad I grew a little
bit of face scruff so you can't see me blushing.
I hope that if you are checking out and enjoying

(57:04):
tech stuff, that you are also checking out some of
Jonathan's other work. We we work together on a number
of weird not just to get rich quick schemes, but
those two and our hair brained inventions. Yeah, our boy.
Let me tell you. If we can boil an egg,
a six minute egg two and a half minutes, it's good.
We've gotten Yeah, it's still poisonous, but yeah, okay, yeah,

(57:26):
you can't eat it, but you can boil it. So
you can also check out I really um, I personally
am a fan of forward thinking, both the video and
the audio series. Uh and it is worth your time
if you ever want to laugh your keystro off. You
can also check out some of Jonathan's work on brain
stuff and what the Stuff. Yeah, you can't even watch

(57:49):
us be twins? Oh man, you might. You might not
want to, you know what. I still like it. It
is very cheesy. I mean, I'm you know, if you
find cheesy humor to be totally cringeworthy, then you probably
don't want to see it. But if you want to
hear me make like the worst James Bond villain style
accident possible. Oh I love it all right, guys. If

(58:11):
you have any other suggestions or tech stuff, whether it
is a topic or a guest host or someone I
should interview, anything like that, or you just have comments
about this particular episode, send them to me. My email
address is tech stuff at how stuff works dot com,
or drop me a line on Facebook, Twitter or Tumbler.
I use tech stuff H s W at All three

(58:32):
and I'll talk to you again really soon for more
on this and happens of other topics. Because it has
to have works dot com