- My name is Matt Steiner.
I'm a senior crime scene analyst.
I'm here today to answer your questions from Twitter.
This is Forensics Support.
S&M79 asks, derp. crime scene photo...
why did they draw chalk around the body?
So this was an old school method that they used to
use to identify where a body was within a crime scene.
Later in our investigation,
after bodies removed
you could see where that body was in its position.
We no longer do this
because of DNA contamination and trace evidence.
So instead of chalk now,
we just take detailed photographs.
We'll document that scene with laser scanner.
That laser scanner is recording millions of points
per second as it's spinning and also taking imaging
as it's turning.
We have that scene preserved virtually.
We can go back and look at a three model.
We could use virtual reality or augmented reality
to go back and walk through that scene virtually
now if we want to.
Forensicfield asks question-
what are the most popular methods
for searching a crime scene?
The three most common ones are a line search,
a grid search and a zone search,
though there are many others.
A line search,
it would be a line of investigators
and they would search a crime scene in one direction.
We search in one direction, we don't find anything,
we could then turn that search at 90 degrees
and search in another direction,
and that's what's called a grid search.
Looking at it at an opposite angle at 90 degrees
sometimes you'll visualize that evidence.
The last most common search is a zone search
where you take a crime scene
you break it down into smaller parts.
As we discover evidence,
we'll go around and we'll mark this evidence
and then we'll take additional photographs
showing that scene with the numbers
and then close up views of the evidence.
So some markers will have a scale on it
to show the the size of it.
What we need to do is have a very systematic
and methodical order that you pick to search these scenes.
Doing things at random, milling about is not acceptable.
JosephV977 asks,
how many people got away with murder
before forensic science improved and DNA?
It's a good question.
I think another good question would be,
how many people were wrongfully convicted
before forensic science?
Science is constantly improving
and our goal is the truth
and we just want our investigation to show that.
Years ago a guy goes out to his car,
a bag of trash next to his door
and he does what a lot of people would do,
he just kicks the bag.
Unbeknownst to him,
there was a pipe bomb in that bag and it detonated.
This is back in 2002 and we had no answers.
2006, I pull some of this evidence from storage
and I reswabbed the wiring and the cap
and the threading to the pipe bomb
and send that off for analysis
because in those short four years,
DNA has advanced.
We identified this person inside of his car.
He had more pipe bombs and automatic weapons.
So sometimes the work that we do not only can solve crimes,
but it could also save lives.
Sibajparker asks,
how do forensics determine shit from blood spatter?
Are there experiments where you crack open dead bodies
with different weapons under different circumstances?
First off, it's not blood splatter.
It's blood spatter.
Blood isn't always red.
It could be different colors and tones.
Blood from your arteries would be bright red,
where the blood from your veins would be a darker color.
As that blood dries,
it gets oxidized.
It's contaminated by the crime scene.
It could also change its color and tone.
If we have a suspect stain and we don't know what it is,
oftentimes we'll do what's called a presumptive test,
like we have here.
This is an OBTI test.
We'll tell you whether that sample could be blood.
You still have to sample it.
You would send it to a laboratory
and they would say what it is
and sometimes to whom it belongs to.
Cadavers though to your question,
generally are not used for blood stain pattern analysis,
but they are used at some universities
and they put bodies in different circumstances.
So they'll put the body in a car,
they'll put it outside in the open in a field,
different environment to see how
those bodies decompose over time.
Lrcf asks,
how did one of the most infamous unsolved crimes
committed on Valentine's Day in 1929
lead to new forensic science techniques
in ballistics and a reform in gun control?
What they're referring to is the Valentine's Day Massacre
in Chicago in 1929.
Seven Irish mobsters were lined up against the wall
and they were shot to death.
The weapons of choice in this crime
was the Thompson submachine gun or Tommy gun.
Back then,
anyone could walk into a store
and purchase one of these weapons.
And because of the public outcry of this case,
we got our first federal gun control law
which took these weapons out of the private sector's hand.
Also with this case was one of the first uses
of forensic ballistic evidence.
Forensic ballistics is the study of not only firearms,
but projectiles and casings related to a firearm
and able to identify certain bullets
or casings to a known firearm.
ScotlandYardCSI asks,
how do we identify human remains?
Well it depends on the state of the remains.
Crime scene investigators work
with a medical examiner's office
or a coroner's office to determine
whether remains are human or not human.
Remains that are in an advanced state of decomposition
to the point where they're skeletal,
generally wanna work with an anthropologist.
They could tell you not only
whether it's human or non-human,
but what part of the body it came from,
possibly the age or the sex of the person
by looking at different bone growth markers
and then sometimes looking at the damage
to these bones could determine the cause
and manner of death.
CXXIV001 asks,
are we sure that every fingerprint is unique?
How is it possible did you check every single one?
No, it's not possible to check every single one.
I didn't check every single one.
They look at first as a category.
They're looking at whether it's a loop,
it's a whirl, it's an arch.
But then really what they're using to identify is
the minutia in your fingerprints.
Anytime, if you look at your fingerprint
that friction ridge split, it comes together,
it starts, it stops, it ends, creates an island.
These are all points of identification
that they're gonna look at.
In the hundred plus years
of analyzing and comparing fingerprints,
they have yet to find two fingerprints that are identical.
Govengie asks,
no seriously,
does anyone know how to do a druggist fold?
Sure, I could show you that now.
A druggist fold or a pharmacy fold
is a way to preserve small amounts
of trace evidence in paper.
The first thing you wanna do with your paper,
you wanna fold it into thirds.
Fold it a third of the way in on both sides,
then you wanna fold it into thirds again.
And then what you wind up,
if you open this up,
is you have nine equal sized boxes.
You would then collect your trace DNA
and you put that trace DNA into the center square.
And then very carefully you want to close that up
and make a little point on one end.
Take this point,
secure it into the pocket on the other end,
and that you have this little bindle now.
Then what you do is you would seal up this one end,
put your signature across it, the date,
and then this would be over packed
into an evidence envelope.
From ChoomieTM,
if our DNA could travel anywhere without us even being there
how reliable is DNA and forensics after all?
DNA analysis gets more sensitive as time moves on,
technology gets better,
it gets more sensitive.
There's different types of crime scene contamination
and there's different types of DNA transfer.
Intra crime scene contamination
happens within the crime scene.
So if I touch this one object,
I touch another object,
I'm contaminating two different objects
within the same scene.
Inter crime scene contamination
is contamination between two unrelated scenes.
I'm at a crime scene,
I'm standing in blood,
that blood is now drying on the soles of my shoes.
I go to another unrelated crime scene.
Now that dried blood is starting to flake off
into that crime scene.
That's inter crime scene contamination.
There's different types of DNA transference events
that can happen.
We have primary,
if I'm not wearing gloves and I touch a door handle,
I'm transferring my skin cells to that door handle.
Secondary contamination would be if you and I shake hands
and now I touch that door handle
and I transfer your skin cells onto that door handle.
When they analyze the DNA,
they could tell the difference
between a major contributor and a minor contributor.
Analyst is not saying you shot that person,
they're just saying that there's a presence
of your DNA on that weapon.
Babiface16 asks,
how in the fuck did OJ Simpson get acquitted?
Literally makes no sense.
The death of Nicole Brown Simpson and Ron Goldman,
it's a roadmap of what not to do at a crime scene.
First off,
there's tons of miscommunication mismanagement
with the case.
Investigators first went to OJ's estate
before going to the crime scene,
so you have this inter crime scene contamination.
When they arrive,
they're told about a bloody patent fingerprint on the gate.
So that's a fingerprint impressed in blood on the gate.
It's probably one of the strongest types of evidence
you can get inside of a crime scene.
That fingerprint was never documented and never collected.
And by the time they realized it
and went back to the scene,
that evidence was gone,
it was cleaned up.
Nicole Brown,
she's outside and to cover her body from the public view
they went inside and they grabbed a blanket
from the home and they covered her with it.
You wanna use a clean sheet to do that.
Not something from someone's home that had already has
who knows DNA on it that can be transferred to the body.
No one knew about DNA,
but since then everyone knows the importance of DNA
with crime scenes.
So the investigators,
no fault to their own,
didn't have these protocols in place
and now most departments do because of this case.
I think if that crime scene happened today
and if OJ really did it,
maybe we'd have a different outcome today.
Vigilantedrones asks,
how are drones helping with crime scene investigation
and accident reconstruction?
It used to be if you wanted to get these overhead views
of your crime scene, you needed a helicopter.
They're expensive,
they're not gonna show up to every crime scene
and there's restrictions on how close
they can get to that scene.
Now we can get a drone that's inexpensive,
easy to use,
and put that right above the scene to get our imagery.
And there's a lot of other amazing things
we could do with drones today.
We could pair this technology with laser scanning
and photogrammetry to get three dimensional models
of our crime scene from the air.
We could put an infrared camera
on our drone to search our crime scene.
Someone might be buried in a certain area,
the soil and the grave is gonna be looser,
so that soil's gonna heat up and cool down
at a different rate and we'll be able to see that
with the drone with infrared.
AidanKohana asks,
big question,
what's the relationship between Sherlock Holmes
and the development of forensic science?
Sherlock Holmes was a fictional character
created
by Arthur Conan Doyle,
used his keen powers of observation,
along with inductive reasoning,
deductive reasoning,
The scientific method applied to criminal investigations
inspired other famous forensic scientists,
notably Dr. Edmond Locard,
the father of forensic science.
Created the first forensic laboratory in Leon, France.
Edmond Locard believed that anytime someone
is at a crime scene, something is transferred,
something is left behind,
and something is taken.
And this is Locard's Principle of Exchange.
EP Security Mag,
digital forensics,
how does it work and why is it significant today?
Digital forensics deals with the documentation,
collection, processing and analysis of data
on digital devices.
It's important because it shows up on every case today.
You walk outside to get a cup of coffee,
how many surveillance cameras did you pass?
We don't walk outside without bringing
our cell phone with us,
that's tracking us everywhere we go.
And if you drive somewhere,
how many surveillance cameras did you pass?
How many traffic cameras did you pass?
How many electronic plate readers did you pass?
Embedded technology and things that surround us,
started with TVs,
but now it's in refrigerators, stoves, and our thermostats.
All this data could be used for an investigation.
UnfoldLabs asks,
how can AI help in solving unsolved crimes?
If you have a crime scene and you have all this
surveillance footage that you gotta look at,
this could take hundreds or even thousands of hours.
You could take AI along with computer vision,
deep learning and object recognition
and train that program to look for certain
objects that's part of the crime.
And what would take hundreds of hours
or thousands of hours can now be done in a fraction of time.
AI's also used in other technology.
One example is the technology that we use
for detection of gunshots.
This software and technology is called Shot Spotter.
Shot Spotter is a series of acoustic sensors that are
set up in different areas that detect and pinpoint gunshots.
This technology uses AI to train itself to differentiate
between gunshots and other loud noises.
Viewpoints Radio asks,
what did detectives rely on to solve a case before
forensic science was part of the toolbox?
Investigators before were doing science-based investigations
use testimonial evidence, interviewing victims,
interviewing witnesses, interrogating suspects,
and investigating alibis.
Forensic science is objective
and testimonial evidence is subjective.
Our eyewitnesses sometimes see something that's not there
or miss something that was there.
Our suspects that are interrogated,
they could lie and even suspects will sometimes admit
to crimes they didn't even commit.
And again your witnesses may be wrong,
your suspects may lie to you,
but your evidence is not gonna lie.
Women In Forensics asks,
how can the communication gap improve
between lawyers and forensic science experts?
As a forensic scientist you have to explain very detailed,
complex scientific ideas to people who don't have the same
education training experience that you do.
For any case no matter how experienced you are,
you always want to prep
with whoever's calling you to testify.
You wanna go over questions that they might ask,
the work that you did,
any sort of errors that you might have made.
You want to that get that out in the open right away.
Also explain any sort of limits
to the analysis that you did.
Eventually when you get to court,
your testimony should be simple enough that the jury
understands it.
I worked with an investigator once
that was testifying and he kept saying
that he was using an ocular enhancement device.
Eventually the defense attorney asked
what's an ocular enhancement device?
And he said, oh, a magnifying glass.
Don't use big language,
talk in simple terms.
Toolkit_masoabi,
but how does forensic science solve murders
that happened 50 years ago?
Just because the cases old doesn't mean
that we can't solve it,
that evidenced still exists,
it still can be analyzed.
Maybe back then 50 years ago,
we only processed that evidence
with conventional fingerprint powder.
But now we could pull that evidence from storage,
we could do DNA analysis on it.
We could do chemical development of fingerprints
and we could use a scanning electron microscope
to look at that evidence at an atomic level
to look at micro traces of DNA.
Every day in the news we see cold cases,
old cases being solved with new technology
and advancements in forensic science.
A good example of this would be
the Golden State Killer case.
You had a series of unsolved homicides and rapes
that was eventually solved with new technology
that is forensic genetic genealogy.
Be able to find out who a relative was of this killer
and from there their investigation
was this old fashioned gumshoe work.
They identified the suspect who at one time
was a police officer,
and eventually they wound up with a tissue
that had his DNA that matched
all these different crime scenes.
Lisa Licata asks,
how are the bodies in the Dead Marshes so well preserved?
So what Lisa's referring to is Pete Moss bogs
in Northern Europe where they have found these
bodies that are preserved for thousands of years
and some of them are really in amazing condition.
Normally when you die,
there's a process that happens.
Whatever the surrounding temperature is,
your body temperature will match that.
And that's called algar mortis.
Also, because your blood is no longer
circulating your blood system,
gravity's gonna pull it down and then what we see
is what's called liver mortis or lividity.
Also, cuz the chemical changes in your muscles,
they will temporarily stiffen,
and this is called rigor mortis.
Besides these processes we have autolysis,
the destruction of cells after they die.
You'll see things like skin slippage.
Your skin will darken
and your cells will continue to break down,
liquefy to the point,
or after a period of time you'll become a skeleton.
So in Northern Europe,
these peat moss bogs are actually a perfect environment
to preserve a body.
They have very little oxygen and they're very acidic.
Bacteria in these environments can't grow
and the body winds up being pickled.
Years ago I was involved in a case,
a woman recalled her stepfather burying a body
in her backyard.
40 years later,
we go to that backyard,
we dig up the exact location
where she said the body was buried
and we find in a plastic garbage bag this body
and the body was really well preserved.
It still had its flesh on it after 40 years.
So sometimes you just get that right amount
of bacteria or no bacteria inside of an environment
and that body becomes preserved.
Rethabilejamar,
is there money in forensics?
Asking for a friend.
If you're getting into forensics for the money,
I would suggest pick a different career.
It's not because you'll be poor,
it's just that it's hard work.
It's a difficult job to do.
You gotta spend hours looking at the same piece of evidence,
looking at the same crime scene.
You gotta really love the work.
Otherwise, years of looking at this evidence
or looking at these crime scenes,
it's gonna feel like a prison sentence.
Well, that's it.
That's all the questions.
I hope you learn something.
Until next time.