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Well it's no small surprise that
finger prints are the most valuable of all of the evidence you can collect
from a crime scene, it doesn't just have practical application in
a criminal investigation, we also use it in our day today lives.
You use finger prints to identify yourself whenever you're trying to gain
access to certain buildings that may be in accordance with your work or
possibly even your home. We use finger prints to identify our self
when we need access to critical account information through banks or
corporations, but when it comes to criminal investigations
the most basic of the evidence items we can collect, is what each
individual person leaves at a crime scene, that's where our fingerprints come into play.
our friction ridges, whenever we touch
something as Lacards exchange principal asserts, we are going to leave
evidence of our presence there. That means there's an exchange of information
and exchange of evidence. Finger prints are going to take
1 of 3 different forms. They are going to be visible meaning that
we can see them with the naked eye, you might also hear this called paten prints
they're going to be impression prints, those that are
left in the surface of whatever we come into contact with, such as you would find
if you contacted a bar of soap, some silly
putty, maybe candle wax. And then you also have latent prints
which are hidden to the naked eye, it doesn't mean they don't exist
because we can't see them, it's just that we have to go through
certain techniques to make those prints visible
when we go through this process of trying to determine what the value is
of the prints we are trying to collect, it's going to make a difference in the collection
technique that we used and then how we try to make those
prints visible. Now the basic materials we're going to be using for this
demonstration today are going to be the ones most of us have in our
homes already or you can easily find at a garage sale. We are going to be using
a basic fishing tank, I've got a
piece of foam that I've got, it's a piece of foam insulation that I've cut to the
dimensions of the top of the tank to use as a sealer, I've
wrapped it in shrink wrap to hold the fumes in so they can react to the
organic compounds in the finger prints. I've also got some
other items here, some of which are going to be the
items we're going to be finger printing today, a soda pop can, a cologne bottle,
maybe another can that was found. but any number of things you could
use in this process, they don't have to be just some sort of can
or small item like that. imp
going to be using for a heat source a candle warmer, I've also got some
hot water in a bowl that's going to be used to create humidity
and then I've got a little container that I'm going to be dropping
several drops of super glue in, in order to start the process
so let's show you how it's actually going to be done.
now there are different methods you can use in order to collect
finger print evidence. You can actually, with some of these methods use
a lifting mechanism in order to actually take the print from the
surface that you can use for analysis and future investigation but you can
also photograph the finger print evidence, when you photograph the finger print evidence
that is very useful in court room settings because those can be enhanced
so that judges and juries can make you know better
informed decisions based on finger prints that you provide in a court room
setting. Now you can use techniques that are of a physical
form, an instrumental form, or even a chemical form
to make latent prints or hidden prints visible to the naked eye
so that you can better collect them or photograph them. Physical forms
are going to be actually applying finger print powders or
enhancers to the prints that will make them more photogenic and allow you to be able
to left the prints from the surfaces. Instrumental forms such as
what you would use in impression prints will allow
you to be able to enhance the print so that you can better photograph the print
such as with the using an forensic light source
on an impression print. Chemical means however
actually takes chemical components and allows those
components to chemically react with the print its self
but in order to do this you have to understand a little bit of the basic knowledge about
what comprises the finger print. We know that finger prints come
from our friction ridges. Lacards principle says that whenever we come
into contact with something, we are going to leave evidence of our presence there.
There are two types of substances that come
out of our friction ridges, liquid,
and solids. The liquids take the form of our
sweat which carries the solids from our body the organic
compounds that are present in our finger prints. Sweat
tends to evaporate though because it's primarily made of water
the organic compounds, they stay behind though as like a
residue in line with our friction ridges. Organic compounds take
the form of amino acids,
riboflavin's, lactic acids that sort of thing
chemical means of collecting finger prints are going to
react with those organic compounds that are left behind
that's where we come to the different sorts of techniques we use
from a chemical stand point that we are going to be talking about today
you can use different chemical reagents, small partial reagents,
in order to spray on to an area that you believe has
latent prints and those will actually react
with the compounds in your finger prints and
allow them to be died a certain color
or be made visible so that you can process them, photographic means or whatever
but you can also use gaseous chemicals in order to
bring latent prints to life.
Now another one of the chemical means that we are going to talk about today
is going to be that of cyanoacrylate fuming
otherwise known as common super glue fuming
a method that was pioneered back in Japan in the 1970s and later brought to the
United States, to the United States Army Criminal Investigation division as well as
as the bureau of alcohol, tobacco, and firearms. What it's going to use is the
actual chemical components that are present in our finger prints
and how they chemically react with the
agents that are present in the super glue. So now I've got my
tank set up. I'm going to explain a little bit about why I have certain things in the
locations that I do in the tank. My hot water is in the center of the tank that's
going to be my source of humidity, it will combine with the chemical reagents,
the gaseous reagents from the super glue, and adhere to the organic
compounds in the finger prints, I want it to be centrally located so it
spreads evenly throughout the tank because the tank is going to be sealed, holding in
the humidity and the gaseous state of the super glue. I have my
warming plate in the corner with the container I will be putting my
super glue in, the warming plate is already turned on, it's warming up
the actual container for the super glue so it speeds up that
transfer of the super glue from its current state into its gaseous state
so I'm going to arrange the items in
the tank in such a way that most of the
gases are going to have easy access to them
now what I've also, am going to do, I'm going to
place a soda can from a hanging fixture that I've attached
to my actual lid made of Styrofoam and I'll be placing that down
on there so it's actually going to be dangling right above the humidity source and well
see what kind of prints we get off of that as well
so we are ready to start the process now. I'm going to
be adding my super glue, several drops, there doesn't have to be a lot
just enough to turn into a gaseous state, and I'm going to add that to the actual
container at this time, ok now
let's get started and watch the process work.
ok it's been several minutes so let's open this up and see exactly what
kind of evidence we have been able to make visible today. Make sure
since you are using gaseous fumes that you are in well-ventilated areas
because when you take this off there is going to be some residual fumes left over, disconnect
your heat source, that way you're not continuing to make fumes while you have that container open
once you have taken those precautions it's good to go ahead and take the lid off and
see what you have got.
Now one of the things to consider is that at any time we're
collecting prints, it's very rare that you're going to get an actual
complete print form either a finger, a digit from your
hand or one of your toes, or a palm print. most of the
time you going to get partial prints and sometimes you're going to have other irregularities
or smuggles in the prints things like that, that keep you from being able to
get an actual perfect print, so that's not something that's a realistic
expectation when you're in the criminal investigation field. We're going to have a look at some of
of the items that we had, we had a cologne bottle, a soda can,
and then a can it could have been a fruit can or something that was
used, one that like you buy from the grocery store, it's had the wrapper taken off of it
and will look and see the type of prints that were made visible
and the benefit that each surface has is to be
able to see those prints. Take for instance
on the cologne bottle which is black which it makes it a really good background
for revealing prints because whenever the chemical reagents
attach to the organic compounds in your print, it's going to
solidify in more of a white form. We can actually
see some pretty good print resolution. As for our soda can
little bit more difficult because there is sporadic color through the
soda can background on there so you have to look a little harder to see the
transfer but you can make out prints just from the casual contact with
the soda can, as for the actual food can. It had the wrapper
taken off of it, well when they make these cans at the factories they put
adhesive in order to allow the wrapper to stick to the can
the adhesive in this case is being really problematic in being able to
actually find a print and make it visible on the can
there may be prints on there but because of the entire adhesive that's on the can we're
dealing with a substances that's also an adhesive cianoacralaester
it's making it really difficult to get any good noticeable prints off this can.