Forensics Expert Explains How to Lift Fingerprints | WIRED

hi I'm Matt Steiner matt is a senior crime scene analyst he explained how crime scenes worked in technique critique so in this case he uses deductive reasoning to come up with the handedness of our victim Louise is a staff writer at Wired matt is going to teach Louie is 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 Plexiglas the first thing we want to 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 Plexiglas 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 powder it's titanium dioxide with some sort of wetting agents for this after we apply powder to it we want to spin off the excess powder okay anything that's good it's always better to add powder than it is to remove powder so we want to add powder slowly to our surface while we're dusting we want to look at the service and we want to use our oblique lighting also so that's gonna help us direct where we're gonna brush we're just going to move it back and forth on the surface and then once I see a fingerprint develop I want to then look at the way the ridge detail is going and follow that pattern all right I don't think I have enough powder even better you're a lot better at this knife oh I see some good but do you see if it's is it a whirl is it a loop is an arch which way are the lines going is it going a circle okay so now take your brush and follow that circle and that's to develop the print a little more oh yeah it's coming out great so we're done with dusting let's go on to lift it take a print packing tape oh yeah I mean it's specifically designed for finger prints oh it's not like super like like very particularly a sticky you'll notice it's very clear so open it up we should be able to see right through so we want to do it one steady Swift motion like so excellent so what I want to do first is gonna start my tape outside of where that print is so I'll start it over here the next thing I want to do is create an anchor point I do that by moving my finger up and down and then what I want to do is smooth my finger across the fingerprint if there's any sort of texture there I want to work my finger in when I'm done we have a fingerprint 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 - got it okay let's make a transfer what we want to do is put our acetate on a clean surface my fingerprint is right there so want to make sure that that gets on the card so the same way that I lifted it I want to put it down and then once it's there I'm gonna rub back and forth and make sure I get out any sort of air bubbles that may be there and there we go my print is now on the acetate now that you master tape lifting I let's move on to something more difficult okay I'm ready so the most ideal service like I said is something that's smooth or 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 in these situations we want to use a product called microsil or any sort of casting type of silicone component okay so the next step now is the 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 wetting agent also so we have our powder and we have two brushes okay we'll take a look at it with the light and we see that there's a really nice fingerprint right there so lightly apply some powder to it so just just it barely gonna happen and now if you see a pattern there follow that arch everything I think we're good okay great so we get some more powder for the golf ball yes try just to move just the tips of the brush and move it back and forth see anything appearing any friction Ridge detail this is a really hard surface huh it is a hard surface or is there any like object shape like that they usually you see besides like doorknobs not this difficult I've had occasion to have textured surfaces that are dimpled like this what kind of objects had a base 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 would have done anything so the next step now is to prepare our microcell and apply it to our surface so this is microcell it's a casting component we use to recover fingerprints or impressions and 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 it's the same length that's all that matters to me makes the blue into the white and I'm just gonna scoop up some of this microcell 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 use that to cast a tool mark impression so now I'm gonna have you mixed up your own batch so you can use this not only for fingerprints you can use it for other sorts of impressions as well yes so how long does it take to drive 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 so what I now put this print on tape like usual or what I just take a photograph of this where would I go next with my little print down here so after we're done recovering this we want to secure it so that fingerprint doesn't get destroyed so we'll put it into a small box 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 so impressive it really works do you think it's gonna work no I mean I thought I was gonna work but it's like it's just so clear yeah no it's really good so you're 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 a night before okay so fingerprints are comprised mostly of water the remaining percentage of fingerprints are mineral salts amino acids and lipids so if it rained that 98 percent of the fingerprint is gone but what remains could be the fatty part of the fingerprint god it's 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 a little DM disulfide that will react with the fats in your fingerprint so is there any technique here that I should be aware of so start the top I'll work your way across and down okay and we'll completely coat this in and you can actually see where it's beating off you could see that reaction between the two yeah I can see a fingerprint right there totally yeah so what we're seeing is just like water would beat off of oil this product is beating off the areas that we have fingerprints we're looking for that reaction and when we want to stop that reaction we want to clean it with some water so just spray spray spray okay 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're trying 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 ah that's right okay I think I see it on there a little bit a little bit okay I think you could have done better okay well again let's just clean that off a bit are there situations where you to hurry out a crime scene yeah I mean if this is outside and it's continually raining and there's no way that we could field that we may have to lift it right away take off a car or something 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 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 payton and plastic Layton is what we already have developed with the fingerprint powder Peyton is where 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 drywall and we're gonna use a chemical to process it to enhance the detail that could be there so we're we're gonna get the blood I actually brought some porous no people are harmed in there no no one was harmed this was 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 cool I just imagine blood to be warm I guess okay so keep going across keep going let's do that let's do one more on this scale what do you usually see is it like really bloody like battered usually yeah you can 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 are gonna give us some more detail so actually if we just look at them now we may see some rich detail we may not actually women have more minutiae the hub tighter Ridge detail than men so sometimes it's more difficult to see woman's fingerprints what about age is that easier to see like an older person's print versus I'm seeing a baby would be really hard versus like someone who's been only aged yeah absolutely that's true but your fingerprints don't change throughout your life if you're a teller or if you worked in masonry sometimes you could wear down your fingerprints all right so I'm gonna do the same thing how often do you see your body fingerprints unfortunately a lot really this is not just a movie thing it's something you see 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 suspects impression in a victim's blood it's like a smoking gun type of evidence it's pretty incriminating huh yes all right so now we're gonna apply leuco crystal violet to our surface so what is the chemical do a lot of presumptive blood agents will have hydrogen peroxide in it and so there's a mixture of leuco crystal violet with hydrogen peroxide that catalytic reaction that we have that hydrogen peroxide will have with the heme group and blood it will turn this product purple to violet for this we're gonna put on masks also because we don't really don't wanna breathe this in so what's the reason for the mask well put it this way this chemical is gonna turn blood into islet purple color we don't want to turn our insides that color got it yeah it's not carcinogenic but we still don't want to 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 see that color change immediately wow it's so bright already we don't see any areas that are still red through the filter paper we could lift this up see how it developed it's so much more clear so if you could see before we didn't see a lot of detail on some of these it start to bring out detail and see even on some of these lighter ones it developed it pretty good so do you use UV light to examine these or do we just do it under like normal light or use a flashlight or something like that yes certain chemicals we use require different wavelengths of light not so much with this but with fluorescent powders certain chemicals like fluorescein will use a specific wavelength of light so now 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 do 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 a value if there's enough points of identification in there for them to make an ID on it once they say that's a value then they'll scan it into the database so there is the local database and then there's a state level and then as a federal database so that's how you looking prints thank you so much for showing me

Channel: WIRED

Views: 1,616,382

Keywords: crime scene analyst, fingerprinting, matthew steiner, fingerprints, fingerprints forensics, lift fingerprints, fingerprint lifting, how to lift fingerprints, pull fingerprints, lifting fingerprints, forensics expert, wired forensics, wired forensics expert, matthew steiner wired, forensics fingerprints, louise matsakis, how to lift fingerprint, fingerprinting wired, how to fingerprint, fingerprint lift, wired

Id: OONfQcGd-uE

Length: 13min 1sec (781 seconds)

Published: Mon Nov 11 2019