Forensics Expert Explains How to Lift Fingerprints

Hi, I'm Matt Steiner.

[Narrator] Matt is a senior crime scene analyst.

He explained how crimes scenes worked in technique critique.

So in this case, he uses deductive reasoning

to come up with the handedness of our victim.

Hey, I'm Louise Matsakis.

[Narrator] Louise is a staff writer at Wired.

Matt is going to teach Louise

how to lift fingerprints from different surfaces,

ranging from easy ones to difficult ones.

So I put my fingerprints on a bunch of stuff.

Where should we start?

Let's start with something easy.

So what do you see here?

What should we be thinking about

when we're looking at this plexiglass?

The first thing we wanna consider is the surface itself.

The most ideal surface for fingerprints

is something that's smooth and non porous

and that's what we got here.

We have plexiglass, it's great for fingerprints.

So now we prepare our fingerprint powder

and our brushes we're gonna use.

What we're gonna do is,

we're gonna coat the brush with powder.

So what's the powder made out of?

For white power, it's titanium dioxide

with some sort of wettening agents.

For this, after we apply powder to it,

we wanna spin off the excess powder.

[Louise] Is that good do you think?

Yeah, that's good.

It's always better to add powder than it is to remove powder

so we wanna add powder slowly to our surface.

While we're dusting, we wanna look at the surface

and we wanna use our oblique lighting also.

So that's gonna help us direct where we're gonna brush.

We're just gonna move it back and forth on the surface

and then once I see a fingerprint develop,

I wanna then look at the way the ridge detail is going

and follow that pattern.

All right, I don't think I have enough powder.

Either that or you're a lot better at this than I,

oh, I see some!

All right, good.

I'm seeing that way.

But do you see, is it a whirl?

Is it a loop?

Is it an arch?

Which way are the lines going?

Is it going in a circle?

Yeah it looks kind of circly,

maybe. Okay so

now take your brush and follow that circle

and that's developed the print a little more.

[Louise] Oh yeah it's coming out great.

So we're done with dusting, let's go on to lifting.

This looks like packing tape.

Yeah I mean it's specifically designed for finger prints.

Oh so it's like super, very particularly sticky?

You'll notice this is very clear.

So if we open it up, we should

be able to see right through it.

So we wanna do it in one steady, swift motion.

Like so.

Excellent.

So what I wanna do first is,

'cause I'm gonna start my tape

outside of where that print is.

So I'll start it over here.

The next thing I wanna do is create an anchor point.

I do that by moving my finger up and down

and then what I wanna do is smooth

my finger across the finger print.

If there's any sort of texture there,

I wanna work my finger in.

When I'm done, we have a finger print.

[Louise] I actually got it guys.

So the next step now is to take

this lift and put it on to an acetate.

Okay what's an acetate?

It's just a piece of plastic that

we're gonna put it on to.

Got it.

Okay let's make a transfer.

What we want to do is put our acetate on a clean surface

and my finger print is right there.

So I wanna make sure that that gets on the card.

So the same way that I lifted it, I wanna put it down.

And then once it's there, I'm gonna rub back and forward

to make sure I get out any sort of

air bubbles that may be there.

[Louise] Oh yeah there's a big one in here.

And there we go.

My print is now on the acetate.

Now that you mastered tape lifting,

let's move on to something more difficult.

Okay I'm ready.

So the most ideal surface, like I said,

is something that's smooth and non porous.

But if we have a surface that isn't smooth, that has

a texture to it, or is curved, it's more difficult.

And in these situations, we'd wanna use a product called

Mikrosil or any sort of casting type of silicone component.

Okay so the next step now is to process these surfaces.

In this case, we have a light colored surface,

so we'll use a black powder.

It's a carbon agent and a wettening agent also.

So we have our powder.

And we have two brushes.

Okay.

We take a look at it with the light and we see

that there's a really nice finger print right there.

So lightly apply some powder to it.

So just to barely--

[sneezing]

Yep. Sorry had powder in my nose.

That's gonna happen.

And now, if you see a pattern there, follow that arch.

[Louise] What do we think?

I think we're good.

Okay great.

Shall we get some more powder for the golf ball?

Yes.

Try just to move just the tips

of the brush, move it back and forth.

See anything appearing?

Any friction ridge detail?

Not too much.

This is a really hard surface huh?

It is a hard surface.

Is there any objects shaped like that

that you usually see besides like doorknobs?

Not this difficult but I've had occasion

to have textured surfaces that are dimpled like this.

Like what kind of objects?

I've had a vase at a crime scene that had

a very textured surface like that and that,

if I was to try to lift it with regular lifting tape,

it wouldn't have done anything.

So the next step now is to prepare

our Mikrosil and apply it to our surface.

So this is Mikrosil.

It's a casting component we use to recover

fingerprints or impressions from difficult surfaces.

So I'll do one from one side of the card to the other

and now I'm gonna draw a line, just below it,

in the hardener and you'll see it's gonna come out thinner.

As long as it's the same length,

that's all that matters to me.

Mix the blue into the white.

And I'm just gonna scoop up some of this Mikrosil

and we're just gonna spread it over.

Just like you would spackle a hole.

All right.

What kind of cases have you used this in before?

Everything from sexual assaults to homicides.

I had a case where someone broke into a house

and they left a tool mark impression

from a screwdriver to break in.

So we used that to cast the tool mark impression.

So now, I'm gonna have you mix up your own batch.

So you can use this not only for fingerprints

but you can use it for other sorts of impressions as well?

Yes.

[upbeat music]

So how long does it take to dry?

Well it depends on the environment but

within 15, 20 minutes it should be dry.

So let's take a look at what we got.

The big reveal.

Whoa.

[Matt] Look at that.

So would I now put this print on tape

like usual or would I take a photograph of this?

Where would I go next with my little print on here?

So after we're done recovering this,

we wanna secure it so that finger print doesn't get

destroyed so we'll put it into a small box,

we'll send this to the lab, they'll take

examination quality photographs of it

and they may have to do other types of enhancement to it.

But these look great like I think you can make

an identification just from these guys.

It's really impressive.

Totally worked.

You didn't think it was gonna work?

No I mean I thought it was gonna

work but it's just so clear.

Yes that was really good.

So you ready for a more difficult situation?

Let's do it.

This bottle is curved which is difficult to begin with.

Let's make it even more difficult,

let's say it rained the night before.

[Louise] Okay.

So fingerprints are comprised mostly of water.

The remaining percentage of fingerprints

are minerals, salts, amino acids and lipids.

So, if it rained, that 98% of the fingerprint is gone

but what remains could be the fatty part of the fingerprint.

Got it so like the oils that were on my finger.

Right so sebaceous glands that you have are secreting oils

and there's products which will react with those lipids.

And make them stand out?

Yeah.

So it's a suspended solution of molybdenum disulfide

that will react with the fats in your fingerprint.

So is there any technique here that I should be aware of?

So start at the top and work your way across and down.

Okay.

And we'll completely coat this thing.

And you can actually see where it's beading off.

You can see that reaction between the two.

[Louise] Yeah I can see

a fingerprint right there, totally.

So what we're seeing is, just like water

would bead off of oil, this product is beading off

the areas that we have fingerprints.

We're looking for that reaction.

And when we wanna stop that reaction,

we wanna clean it with some water.

So just spray, spray, spray.

Wow that's crazy.

It just stays right on there.

How often do you use this technique?

So it's good for surfaces that are wet.

It also works really well on greasy surfaces.

So if I had a crime scene in a kitchen

and there's a layer of grease on everything,

if you try to dust it, you're just

gonna spread that grease around.

So what I want you to do is the same technique

we used before to lift it, you're gonna do the same thing

just notice that it's gonna be a little more difficult.

[Louise] Ah! That's right.

Okay I think I see it on there a little bit maybe.

A little bit.

I think you could've done better.

Okay well--

Again, let's just clean that off a bit.

[Louise] Are there situations

where you have to hurry at a crime scene?

Yeah I mean if this is outside and it's continually

raining and there's no way that we could shield that,

we may have to lift it right away.

[Louise] Like off a car or something that was outside?

So then we would take this print

and we'd transfer it to a card.

Would you like draw a picture of the bottle?

Yeah absolutely we'd draw a diagram of the bottle

and like circle or draw an arrow

to where we got the print from.

So now, we'll make it harder on ourselves,

what if we have a bloody fingerprint?

So we have three different types

of impressions at a crime scene.

We have latent, patent and plastic.

Latent is what we already have

developed with the fingerprint powder.

Patent is where's it's impressed in some sort of substance.

So blood, mud, oil.

A plastic print is impressed in a soft surface.

So we're gonna create some bloody fingerprints

on our dry wall and we're gonna use a chemical

to process it to enhance the detail that could be there.

So where we gonna get the blood?

I actually brought some for us.

No people were harmed in the...

No no one was harmed.

This is taken with someone's permission.

It's actually been treated so it's very safe.

We could actually drink that if we wanted to.

It's very cold.

I just imagine blood to be warm I guess.

Okay so keep going across.

Keep going.

Let's do another one, do a little bit below that.

Do another one.

Let's do one more.

On this scale what do you usually see?

Is it like really bloody like that or do you usually see

more like this one? Yeah you can see

anywhere in between.

So you would think like the bloodier ones

are your better ones but it's usually

the lighter ones that're gonna give us more detail.

So actually if we just look at them now,

we may see some ridged detailing, may not.

Actually women have more minutiae,

they'll have tighter ridged detail than men.

So sometimes it's more difficult

to see women's finger prints.

What about age?

Is it easier to see like an older person's print versus,

I'm assuming like a baby would be really hard

versus like someone who's middle aged.

Yeah absolutely, that's true.

But your finger prints don't change throughout your life.

If you're a teller or if you work in masonry,

sometimes you can wear down your fingerprints.

All right so I'm gonna do the same thing.

How often do you see bloody fingerprints?

Unfortunately a lot.

Really?

So this is not just a movie thing?

It's something you see quite often?

No, yeah.

But it is like the best type of evidence that we can get

so if we have the victim's blood

and we have the suspect's impression in that victim's blood,

it's like a smoking gun type of evidence.

That's pretty incriminating huh?

Yes.

All right so now we're gonna apply

leucocrystal violet to our surface.

So what does the chemical do?

A lot of presumptive blood agents

will have hydrogen peroxide in it and so there's

a mixture of leucocrystal violet with hydrogen peroxide,

that catalytic reaction that we have,

that hydrogen peroxide will have with the heme group

in blood, will turn this product purple to violet.

For this we're gonna put on masks

also 'cause we really don't wanna breathe this in.

So what's the reason for the mask?

Well, put it this way, this chemical's

gonna turn blood into violet, purple color.

We don't wanna turn our insides that color.

Got it yeah, that's definitely not what I want.

It's not carcinogenic but we

still don't wanna breathe it in.

So we'll cover these areas with filter paper

and then we're just gonna spray

the chemical right on top of it.

Can see that color change immediately.

[Louise] Wow it's so bright already.

If we don't see any areas that are still red, through the

filter paper, we can lift this up and see how it developed.

[Louise] It's so much more clear.

So if you can see, before we didn't see a lot of detail

in some of these, it start to bring out detail.

And even on some of these lighter ones,

it developed it pretty good.

So do you use UV light to examine these

or would you just do it under like normal light

or use a flashlight or something like that?

Yeah certain chemicals we use

require different wavelengths of light.

Not so much with this but, with fluorescent powders,

certain chemicals like fluorescein,

we'll use a specific wavelength of light.

So would the next step be to take a photo

or would you bring the tape out again?

So we would first photograph it as is.

So we would take a close up macro shot

of these fingerprints before we process them

and then we would photograph them again.

And then what we could is just cut the surface out

and send it to the lab because there's other steps

that they could do at the lab that we can't do in the field.

So after you collect the fingerprints,

how are they analyzed?

What sorts of databases are you checking them against?

When we're done recovering the fingerprints,

we create a report for that and then we send the report,

with our fingerprints to an analyst.

The analyst will first look at the fingerprints

to first say they're of value or they're not of value.

If there's enough points of identification in there

for them to make an ID on it.

Once they say that it's of value,

then they'll scan it into the database.

So there is the local database and then there is

a state level and then there's a federal database.

So that's how you lift fingerprints.

Thank you so much for showing me.