Forensics Expert Answers Crime Scene Questions From Twitter

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.