February 9, 2010 • 9 mins
To forensic scientists, a bloodstain is more than just a grisly ornament at a crime scene -- so what exactly do they do with it? Turn in and learn more about bloodstain pattern analysis in this episode.
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Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:01):
Welcome to Stuff from the Science Lab from how stuff
works dot com. Hey guys, and welcome to the podcast.
This is Alice and Ladermilk, the science editor how stuff
works dot com. And this is Robert lamb Signs, writer
for how stuff works dot Com. Today we're talking about blood. Blood. Yes,
(00:25):
what it can tell us. It turns out, it can
tell us a lot. Right. You can tell it's circulating
in your blood stream at any given point. Yeah, you
can tell you know, what kind of diet you have,
what you need to cut out blood pressure. Yeah. Sure,
And as it turns out, at a particularly bloody violent
crime scene, you can maybe tell how that have that
crime happened. Yeah, because as we we all know, when
(00:46):
you murder somebody, sometimes blood comes out. And by examining
just how that blood came out, you know, you can
determine all sorts of interesting facts like what kind of
weapon was used, how many lows or shots they sustained, indeed,
who where and how right. So it's kind of like
maybe you could even figure out the game of Clue. Yeah,
(01:08):
it's it's a lot like Clue that with less reliance
on like dice rolling and moving from one room and
Parker Brothers, etcetera. Yes, so today we're going to tell you,
based on the branch of forensic science called blood stained
pattern analysis, that it was Colonel Mustard who murdered the
suspect in the library with the candlesticks, and we figured
(01:29):
it out with blood stained pattern analysis. That's right, Okay,
So let's start with the easiest thing first, which is right,
that's the library, because that's the room with the blood
all over it, right, and and you know that's that's
really a crucial thing. It's like how much blood is
in there, Like clearly there's a whole lot of blood.
There's like a lethal amount of blood in a room.
Then you know that that's probably where you know the
(01:51):
mess happened, but you could have a little mess tracked
elsewhere if said person, you know, stumbled around wander to
go right, a less weel and testament. But then another
thing that we have in the library is we have
blood spray on the walls. We do, yeah, we kind
of blood spray. Funny that you should ask that because
there are three different varieties of blood spatter that you
(02:13):
can find. It's based on velocity. All based on velocity,
just how fast the drop is going How how the
shape of the blood drop, what holds up to that velocity?
And what kind of blow your inflicting? Right right, yeah,
because the weapon you're using, because the faster the blood
is traveling, the smaller the droplet, right right, So let's
start off with the easy one, low velocity, right, So
(02:33):
this is going to be something that force of impact
is five ft per second or less. And this is
where you're gonna have your big fat drops, although they're
not that fat really, they're only between four and eight millimeters. Yeah.
This is the kind of blood spatter you could just
have around the house on just a normal day when
you haven't killed anybody, right, Like you're peeling a fruit
or something, you cut yourself, sat, you got blood on
(02:55):
the kitchen floor. Yeah right, right, So we have a
couple of these drops at the scene, but they're not
really the bulk. Yeah, this are this is the kind
of thing that could on a crime scene, falls from
the wound, you know, falls off the murder weapon. But yeah,
the bulk of this, we're looking at medium velocity spatter. Yeah, alright,
so numbers on this this is something and this is
this would be incurred with an external force of greater
(03:16):
than five ft per second, but less than ft per second.
So these, um, these little blood drops are smaller, right,
And this is the blood drops involved in this type
of spatter are concurrent with something from blunt or sharp trauma,
say the clue weapon a candlestick maybe, or the lead
pipe or the wrench battle. But this is not really
(03:38):
going to be the revolver or the rope or I
forget what the what are the other clue weapons there?
We have the revolver, the rope, I think, I think,
I think it's yeah. Yeah, yeah. So based on this
and looking at the wounds on the body, we know
that the victim died from blunt trauma. We also know
it wasn't the dagger, right because there are no knife wounds. Right,
But if had they used the knife, we would it
(04:00):
would have been consistent with the medium velocity spatter. Yeah. Yeah,
And then you can also get the time kind of
spatters from arterial spurts and gushes. Yeah, there's some major
veins close to the surfaces of the skin, and you
could easily rip those open with a you know, a
well placed below to the head. Sounds like experience with this, Robert, Well, so,
(04:21):
for our purposes, we mainly have this medium velocity blood spatter.
We don't have any of that high velocity blood spatter.
And this is going to be your mist right, your
finest spray. This is like exit wound from a gunshot
or an explosion, I'm sorry, or an explosion or explosive
I should say, um, deadly sneeze, deadly sneeze, a bloody cough.
(04:42):
But typically gunshot wounds is where you're gonna find this
high velocity blood spatter. So now we know, right, it
happened in the library with the candlestick for our purposes,
although it technically could have been the lead piper some
other but it was definitely blunt trauma, definitely blunt. But
who was it? Who was it? Indeed, well it was
(05:04):
Colonel Mustard of course and that but one of the
reasons we uh, we could know this is based on
the handedness of the assailant by analyzing the way the
blood has flattered from from the what they call the
the area of convergence. That's like that's where that's like
ground zero for whatever sling and blood all over the library, uh,
(05:24):
in this case of wounds or something. If you're to
see dexter or something, and you see all those strings.
Typically the strings are leading to an area of convergence, right,
and that's that's that's the key area. Yeah. And by
applying behind like trigonometry and another complicated equations to this,
so they can actually figure out what's the assailant right
handed or left handed in this case, Colonel Mustard only
(05:46):
left handed suspect. Yeah, it's definitely Colonel Mustard. Then there's
also something we'd like to call voids comes void. It's
like if you're you're standing out in front of a
brick wall at night and somebody shins a light on you,
maam you the shadow behind you. The rest of the
wall is light. Now imagine instead of light, you have
like a whole bunch of arterial spray. Right, You're gonna
(06:07):
have that one section outlining up, you know, like a
cartoon outline where there's no blood. Right. So so they
look for that at crime scenes because if you see,
if they can see a void in the in the
spray and in the spatter, then that could be where
the assailant was standing and could even tell us a
little a little about the physical characteristics. So for the person,
like say if they had a mustache, right, Uh, yeah,
(06:28):
because Colonel Mustard does have a substantial mustache, though it's
possible it could be outlined. Okay, so now we know
it is Colonel Mustard in the library with the camel stick.
I win, you win, We both winn. Mustard goes to jail.
The library is safe again, Yeah, no doubt. Okay, But
as you guys can tell, blood stained pattern analysis isn't
going to be the only evidence that lawmakers are going
(06:50):
to use to prosecute a possible suspect, right, Yeah, it's
just one tool in an investigator or a prosecutor's a toolbox. Well,
this one case, the blood stained pattern elysis might have
come in handy. It was the famous do you want
to do it? You do it? You're Australia. Didn't go
eat my baby? There you go. Yes, they didn't go
eat my baby. It's made famous by Seinfeld. Yes, Elaine,
(07:12):
thank you Elaine for that and many other things. So
what happened in this case, Well, it's Australia. Woman's out
in the wilderness to walk about with your family, it
really walk about? No, I think she's just camping, but yeah,
she's out with her family. And then uh, and she
comes back, babies apparently gone. Right, So she puts her
kids to bed and baby's gone. Baby's gone. Baby by
(07:36):
the name of Azaria area. And according the claim is
that whoops, dingo came took the baby away. Well, people
didn't believe that, right, and she was prosecuted. They thought
that they thought she murdered her baby and it wasn't
the dingo. If the authorities investigating the crime had used
proper evidence handling techniques and use blood stained pattern analysis properly,
(07:57):
they might have had a better time bolstering their case. Yeah.
I think it came down to the amount of blood
at the crime scene, in the tent if you in
the tent um, that seemed to seem to suggest that
maybe that the dingo didn't come in and carry a
baby away as much as something violent happened to the
baby in the tent right, And and again this isn't
(08:17):
This is necessarily a case where oh, if they'd only
apply trigonometry to the crime scene. It all comes down
to the base basically understanding the properties of blood, the
physical properties of blood and how that relates to blood spatter. Yeah,
so blood stained pattern analysis, it's a bloody business, but
you can learn more about it at hous to works
(08:38):
dot com. And we have all sorts of creepy other
CSS stuff, body farms, forensic dentistry, just tons of bloody articles. Yeah,
and check out our spefy side stuff blog it blogs
that hows to works dot com too. We post on
all sorts of creepy stuff there too. Thanks for listening, guys.
(09:01):
For more on this and thousands of other topics, visit
how stuff works dot com. Want more how stuff works,
check out our blogs on the how stuff works dot
com home page
Welcome to Stuff from the Science Lab from how stuff
works dot com. Hey guys, and welcome to the podcast.
This is Alice and Ladermilk, the science editor how stuff
works dot com. And this is Robert lamb Signs, writer
for how stuff works dot Com. Today we're talking about blood. Blood. Yes,
(00:25):
what it can tell us. It turns out, it can
tell us a lot. Right. You can tell it's circulating
in your blood stream at any given point. Yeah, you
can tell you know, what kind of diet you have,
what you need to cut out blood pressure. Yeah. Sure,
And as it turns out, at a particularly bloody violent
crime scene, you can maybe tell how that have that
crime happened. Yeah, because as we we all know, when
(00:46):
you murder somebody, sometimes blood comes out. And by examining
just how that blood came out, you know, you can
determine all sorts of interesting facts like what kind of
weapon was used, how many lows or shots they sustained, indeed,
who where and how right. So it's kind of like
maybe you could even figure out the game of Clue. Yeah,
(01:08):
it's it's a lot like Clue that with less reliance
on like dice rolling and moving from one room and
Parker Brothers, etcetera. Yes, so today we're going to tell you,
based on the branch of forensic science called blood stained
pattern analysis, that it was Colonel Mustard who murdered the
suspect in the library with the candlesticks, and we figured
(01:29):
it out with blood stained pattern analysis. That's right, Okay,
So let's start with the easiest thing first, which is right,
that's the library, because that's the room with the blood
all over it, right, and and you know that's that's
really a crucial thing. It's like how much blood is
in there, Like clearly there's a whole lot of blood.
There's like a lethal amount of blood in a room.
Then you know that that's probably where you know the
(01:51):
mess happened, but you could have a little mess tracked
elsewhere if said person, you know, stumbled around wander to
go right, a less weel and testament. But then another
thing that we have in the library is we have
blood spray on the walls. We do, yeah, we kind
of blood spray. Funny that you should ask that because
there are three different varieties of blood spatter that you
(02:13):
can find. It's based on velocity. All based on velocity,
just how fast the drop is going How how the
shape of the blood drop, what holds up to that velocity?
And what kind of blow your inflicting? Right right, yeah,
because the weapon you're using, because the faster the blood
is traveling, the smaller the droplet, right right, So let's
start off with the easy one, low velocity, right, So
(02:33):
this is going to be something that force of impact
is five ft per second or less. And this is
where you're gonna have your big fat drops, although they're
not that fat really, they're only between four and eight millimeters. Yeah.
This is the kind of blood spatter you could just
have around the house on just a normal day when
you haven't killed anybody, right, Like you're peeling a fruit
or something, you cut yourself, sat, you got blood on
(02:55):
the kitchen floor. Yeah right, right, So we have a
couple of these drops at the scene, but they're not
really the bulk. Yeah, this are this is the kind
of thing that could on a crime scene, falls from
the wound, you know, falls off the murder weapon. But yeah,
the bulk of this, we're looking at medium velocity spatter. Yeah, alright,
so numbers on this this is something and this is
this would be incurred with an external force of greater
(03:16):
than five ft per second, but less than ft per second.
So these, um, these little blood drops are smaller, right,
And this is the blood drops involved in this type
of spatter are concurrent with something from blunt or sharp trauma,
say the clue weapon a candlestick maybe, or the lead
pipe or the wrench battle. But this is not really
(03:38):
going to be the revolver or the rope or I
forget what the what are the other clue weapons there?
We have the revolver, the rope, I think, I think,
I think it's yeah. Yeah, yeah. So based on this
and looking at the wounds on the body, we know
that the victim died from blunt trauma. We also know
it wasn't the dagger, right because there are no knife wounds. Right,
But if had they used the knife, we would it
(04:00):
would have been consistent with the medium velocity spatter. Yeah. Yeah,
And then you can also get the time kind of
spatters from arterial spurts and gushes. Yeah, there's some major
veins close to the surfaces of the skin, and you
could easily rip those open with a you know, a
well placed below to the head. Sounds like experience with this, Robert, Well, so,
(04:21):
for our purposes, we mainly have this medium velocity blood spatter.
We don't have any of that high velocity blood spatter.
And this is going to be your mist right, your
finest spray. This is like exit wound from a gunshot
or an explosion, I'm sorry, or an explosion or explosive
I should say, um, deadly sneeze, deadly sneeze, a bloody cough.
(04:42):
But typically gunshot wounds is where you're gonna find this
high velocity blood spatter. So now we know, right, it
happened in the library with the candlestick for our purposes,
although it technically could have been the lead piper some
other but it was definitely blunt trauma, definitely blunt. But
who was it? Who was it? Indeed, well it was
(05:04):
Colonel Mustard of course and that but one of the
reasons we uh, we could know this is based on
the handedness of the assailant by analyzing the way the
blood has flattered from from the what they call the
the area of convergence. That's like that's where that's like
ground zero for whatever sling and blood all over the library, uh,
(05:24):
in this case of wounds or something. If you're to
see dexter or something, and you see all those strings.
Typically the strings are leading to an area of convergence, right,
and that's that's that's the key area. Yeah. And by
applying behind like trigonometry and another complicated equations to this,
so they can actually figure out what's the assailant right
handed or left handed in this case, Colonel Mustard only
(05:46):
left handed suspect. Yeah, it's definitely Colonel Mustard. Then there's
also something we'd like to call voids comes void. It's
like if you're you're standing out in front of a
brick wall at night and somebody shins a light on you,
maam you the shadow behind you. The rest of the
wall is light. Now imagine instead of light, you have
like a whole bunch of arterial spray. Right, You're gonna
(06:07):
have that one section outlining up, you know, like a
cartoon outline where there's no blood. Right. So so they
look for that at crime scenes because if you see,
if they can see a void in the in the
spray and in the spatter, then that could be where
the assailant was standing and could even tell us a
little a little about the physical characteristics. So for the person,
like say if they had a mustache, right, Uh, yeah,
(06:28):
because Colonel Mustard does have a substantial mustache, though it's
possible it could be outlined. Okay, so now we know
it is Colonel Mustard in the library with the camel stick.
I win, you win, We both winn. Mustard goes to jail.
The library is safe again, Yeah, no doubt. Okay, But
as you guys can tell, blood stained pattern analysis isn't
going to be the only evidence that lawmakers are going
(06:50):
to use to prosecute a possible suspect, right, Yeah, it's
just one tool in an investigator or a prosecutor's a toolbox. Well,
this one case, the blood stained pattern elysis might have
come in handy. It was the famous do you want
to do it? You do it? You're Australia. Didn't go
eat my baby? There you go. Yes, they didn't go
eat my baby. It's made famous by Seinfeld. Yes, Elaine,
(07:12):
thank you Elaine for that and many other things. So
what happened in this case, Well, it's Australia. Woman's out
in the wilderness to walk about with your family, it
really walk about? No, I think she's just camping, but yeah,
she's out with her family. And then uh, and she
comes back, babies apparently gone. Right, So she puts her
kids to bed and baby's gone. Baby's gone. Baby by
(07:36):
the name of Azaria area. And according the claim is
that whoops, dingo came took the baby away. Well, people
didn't believe that, right, and she was prosecuted. They thought
that they thought she murdered her baby and it wasn't
the dingo. If the authorities investigating the crime had used
proper evidence handling techniques and use blood stained pattern analysis properly,
(07:57):
they might have had a better time bolstering their case. Yeah.
I think it came down to the amount of blood
at the crime scene, in the tent if you in
the tent um, that seemed to seem to suggest that
maybe that the dingo didn't come in and carry a
baby away as much as something violent happened to the
baby in the tent right, And and again this isn't
(08:17):
This is necessarily a case where oh, if they'd only
apply trigonometry to the crime scene. It all comes down
to the base basically understanding the properties of blood, the
physical properties of blood and how that relates to blood spatter. Yeah,
so blood stained pattern analysis, it's a bloody business, but
you can learn more about it at hous to works
(08:38):
dot com. And we have all sorts of creepy other
CSS stuff, body farms, forensic dentistry, just tons of bloody articles. Yeah,
and check out our spefy side stuff blog it blogs
that hows to works dot com too. We post on
all sorts of creepy stuff there too. Thanks for listening, guys.
(09:01):
For more on this and thousands of other topics, visit
how stuff works dot com. Want more how stuff works,
check out our blogs on the how stuff works dot
com home page
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