WEBVTT - The Cutting Edge of Forensic Technology 0:00:04.120 --> 0:00:07.160 Get in touch with technology with tech Stuff from how 0:00:07.200 --> 0:00:14.280 stuff Works dot com. Hey there, and welcome to tech Stuff. 0:00:14.280 --> 0:00:17.079 I'm your host, Jonathan Strickland. I'm an executive producer with 0:00:17.120 --> 0:00:19.720 how Stuff Works in I Love all Things Tech. And 0:00:19.760 --> 0:00:24.000 in our last episode, I traced the history and evolution 0:00:24.239 --> 0:00:27.480 of forensic science and how it kind of grew up 0:00:27.520 --> 0:00:30.480 of out of a bunch of other kind of parallel 0:00:30.560 --> 0:00:35.879 developing areas of investigation. And today we look at forensic 0:00:35.920 --> 0:00:41.920 science as a collection of these various techniques and technologies 0:00:42.320 --> 0:00:46.840 to to investigate crime and to solve crime. So today 0:00:47.120 --> 0:00:49.479 I wanted to look more at some of the actual 0:00:49.600 --> 0:00:52.720 tech use. I was kind of light on the tech 0:00:53.360 --> 0:00:56.360 in the last episode. I was talking more about the 0:00:56.400 --> 0:01:00.120 evolution of the ideas behind it, because that really informs 0:01:00.280 --> 0:01:04.120 how the tech itself evolved. And today we're gonna look 0:01:04.120 --> 0:01:06.520 a little more closely at that now. In the last episode, 0:01:06.560 --> 0:01:13.080 I did mention the comparison microscope, that is a microscope 0:01:13.120 --> 0:01:17.399 that is typically a pair of light microscopes. Isn't the 0:01:17.520 --> 0:01:22.520 microscopes that use light as the medium to magnify stuff 0:01:22.520 --> 0:01:27.640 into your eyeballs, So the companion or comparison microscope is 0:01:27.680 --> 0:01:30.080 a pair of these right, it's it's essentially side by 0:01:30.120 --> 0:01:35.080 side two light microscopes that are actually bridged together, but 0:01:35.160 --> 0:01:38.839 on casual glance it looks almost like kind of binoculars 0:01:38.959 --> 0:01:41.600 in a way. And here's a quick rundown on how 0:01:41.720 --> 0:01:45.800 light microscopes work so that you can understand what a 0:01:45.800 --> 0:01:50.240 comparison microscope is able to do. A basic upright light 0:01:50.320 --> 0:01:54.120 microscope the kind you might see in a high school 0:01:54.200 --> 0:01:56.520 lab or even you know, I guess elementary school and 0:01:56.520 --> 0:01:59.200 middle school labs. Now when when I was a student, 0:01:59.240 --> 0:02:01.040 they didn't let a play with us until we were 0:02:01.160 --> 0:02:05.240 essentially high schoolers. But you are probably familiar what what 0:02:05.360 --> 0:02:08.000 these look like. It's that little upright microscopees gun. I 0:02:08.160 --> 0:02:12.120 piece at one end has a little platform it's called 0:02:12.160 --> 0:02:15.720 the stage where you would put a sample to h 0:02:15.840 --> 0:02:19.200 to examine. Well, they're called light microscopes because they have 0:02:19.240 --> 0:02:23.720 a light source at the base. Typically, your basic upright 0:02:23.760 --> 0:02:27.360 light microscope does that shines light up through a sample 0:02:27.400 --> 0:02:29.560 so that you can see it when you're looking through 0:02:29.600 --> 0:02:33.640 the I piece above. The light source is a special 0:02:33.840 --> 0:02:38.240 lens called a condenser. Now, the condenser's purpose is to 0:02:38.760 --> 0:02:42.440 redirect a divergent beam of light from a light source 0:02:42.760 --> 0:02:46.239 into a converging beam to illuminate a sample. So essentially 0:02:46.280 --> 0:02:51.200 you're focusing light on the smaller area that the sample 0:02:51.280 --> 0:02:54.360 itself will sit on, and of course that is on 0:02:54.760 --> 0:02:57.440 the part of the microscope that's called the stage. The 0:02:57.520 --> 0:03:01.760 microscope has what is called an objective lens that's near 0:03:01.800 --> 0:03:04.840 the end opposite where you put your eye, so this 0:03:04.919 --> 0:03:08.040 is the end that's closest to the sample. Uh. The 0:03:08.120 --> 0:03:10.320 lens that's close to your eye, by the way, is 0:03:10.400 --> 0:03:14.640 fittingly called the ocular lens. So the objective lens and 0:03:14.639 --> 0:03:18.120 the condenser are aligned to focus on the same spot 0:03:18.240 --> 0:03:21.560 of a sample, so the light from the condenser is 0:03:21.639 --> 0:03:25.200 hitting the same region of a sample that the objective 0:03:25.280 --> 0:03:29.400 lens is focused on. The job of the objective lens 0:03:29.440 --> 0:03:32.320 is to gather light from the point of observation and 0:03:32.400 --> 0:03:36.640 focus that light to produce a real image. Objective lenses 0:03:36.680 --> 0:03:39.680 are in stuff like cameras and telescopes to they're not 0:03:39.880 --> 0:03:43.640 just in microscopes. The lenses in the eyepiece of the 0:03:43.680 --> 0:03:48.040 microscope do the majority of the actual magnification. So with 0:03:48.160 --> 0:03:52.839 light microscopes you can sometimes swap out the objective lens, 0:03:52.880 --> 0:03:55.840 but rarely can you swap out the eye piece. Uh. 0:03:56.200 --> 0:03:59.080 The reason you would swap out the objective lens is 0:03:59.160 --> 0:04:03.240 because it does affect the magnification somewhat. A more flat 0:04:03.240 --> 0:04:06.920 objective lens will have a lower magnification than a rounder 0:04:07.000 --> 0:04:11.080 objective lens. This is all due to the physics of optics, 0:04:11.080 --> 0:04:13.240 which I'm not going to go into here because without 0:04:13.920 --> 0:04:18.360 visual aids, I would be struggling to describe them accurately. 0:04:19.000 --> 0:04:21.720 The purpose of swapping out those objective lenses is to 0:04:21.760 --> 0:04:25.360 focus on either larger or smaller areas of a sample. 0:04:26.200 --> 0:04:28.080 So if you need to look at really small regions 0:04:28.080 --> 0:04:32.679 of a sample, you'll want a rounder objective lens, and 0:04:32.760 --> 0:04:37.880 this will let you look at the very tiny regions 0:04:37.880 --> 0:04:41.040 of a sample. A comparison microscope is, like I said, 0:04:41.080 --> 0:04:43.920 a pair of these light microscopes and allows you to 0:04:44.040 --> 0:04:47.440 view two samples at the same time. That lets you 0:04:47.520 --> 0:04:51.480 compare those two samples, and you can eliminate the necessity 0:04:51.560 --> 0:04:55.920 to rely upon memory when comparing one sample with another, 0:04:56.000 --> 0:04:58.240 and in the case of forensics, that's incredibly important. You 0:04:58.320 --> 0:05:03.360 might be comparing a bullet that was retrieved from a 0:05:03.400 --> 0:05:08.200 crime scene with a bullet that you have fired from 0:05:08.240 --> 0:05:12.400 a firearm that you suspect was used at that crime scene. 0:05:12.680 --> 0:05:15.360 So you want to see if these two bullets were 0:05:15.360 --> 0:05:18.320 in fact fired out of the same firearm, and you 0:05:18.320 --> 0:05:21.520 want to be able to compare the markings on bullet 0:05:21.560 --> 0:05:25.400 one versus bullet Too. But if you were just having 0:05:25.440 --> 0:05:29.760 to swap them out underneath the same microscope, you would 0:05:29.760 --> 0:05:32.680 have to remember, all right, well, the markings I saw 0:05:32.680 --> 0:05:35.360 on bullet one, do they match up to what I'm 0:05:35.360 --> 0:05:38.359 seeing now in bullet too. With a comparison microscope, you 0:05:38.400 --> 0:05:41.320 can look at them side by side in real time, 0:05:41.640 --> 0:05:44.240 and that's much more reliable than looking at one sample 0:05:44.320 --> 0:05:46.599 than removing it from the microscope, putting in a second 0:05:46.600 --> 0:05:50.920 sample and then saying, huh, I think this looks the same. 0:05:51.279 --> 0:05:55.400 So it it took a lot of ambiguity out of investigation. Now. 0:05:55.520 --> 0:05:58.120 Light microscopes are really useful, but sometimes you gotta go 0:05:58.160 --> 0:06:01.080 a little further than what light microscope can do. They 0:06:01.120 --> 0:06:04.520 have limitations on the amount of magnification they can provide, 0:06:04.960 --> 0:06:07.839 and that's where you might want to up your game 0:06:07.880 --> 0:06:11.880 a bit go with something like a scanning electron microscope. 0:06:12.560 --> 0:06:16.040 Those microscopes can magnify a sample up to three hundred 0:06:16.400 --> 0:06:22.360 thousand times. It is an enormous amount of magnification. And 0:06:22.560 --> 0:06:25.880 a scanning electron microscope can also have depth of field, 0:06:26.080 --> 0:06:28.640 like really good depth of field, to the point where 0:06:29.040 --> 0:06:31.880 you will end up with an image that is almost 0:06:31.960 --> 0:06:35.400 three D in nature. The s c M can or 0:06:35.560 --> 0:06:39.400 scanning electron microscope can tell researchers a lot about the 0:06:39.480 --> 0:06:43.120 composition of a sample, so not just what it looks like, 0:06:43.240 --> 0:06:46.719 but the stuff that it's made out of. So we 0:06:46.720 --> 0:06:49.159 should talk about how these work because it's simple to 0:06:49.200 --> 0:06:53.120 say scanning electron microscope, but what does that really mean. Well, 0:06:53.480 --> 0:06:58.840 back in two scientists developed a precursor to this, called 0:06:58.880 --> 0:07:02.960 the transmission electron microscope or t e M, and that 0:07:03.040 --> 0:07:06.000 microscope would direct a beam of electrons through a sample 0:07:06.120 --> 0:07:11.360 to create a projectable image. Scanning electron microscopes followed soon afterward. 0:07:11.440 --> 0:07:13.960 They were developed in nineteen five, just a couple of 0:07:14.000 --> 0:07:17.240 years later, and initially they didn't get a whole lot 0:07:17.240 --> 0:07:22.080 of support in the scientific community. Uh, partly because the 0:07:22.120 --> 0:07:26.360 transmission electron microscopes that just come out we're already seen 0:07:26.400 --> 0:07:29.000 to have covered that territory. Scientists are saying, well, why 0:07:29.000 --> 0:07:33.160 should we spend money developing this new technology. We already 0:07:33.160 --> 0:07:36.000 have this other one that seems to do the same thing. Ultimately, 0:07:36.040 --> 0:07:38.840 scanning electron microscope showed that they had features that made 0:07:38.880 --> 0:07:42.720 them appealing on their own. So your basic scanning electron 0:07:42.880 --> 0:07:46.720 microscope consists of the following parts, and it is very 0:07:46.760 --> 0:07:49.920 different in many ways from a light microscope. You're not 0:07:50.080 --> 0:07:52.120 looking through an eyepiece the way you would with a 0:07:52.200 --> 0:07:56.440 light microscope. First of all, the entire guts of the 0:07:56.480 --> 0:08:00.800 scanning electron microscope are inside a vacuum chamber. The microscope 0:08:00.800 --> 0:08:04.080 itself is sealed in such a way that there is 0:08:04.120 --> 0:08:07.040 a vacuum inside of it. And it has to be 0:08:07.160 --> 0:08:11.480 like that because you're using electrons as you're scanning medium. 0:08:11.600 --> 0:08:15.200 You don't want to have any interference from particles or 0:08:15.240 --> 0:08:20.680 even air molecules. Those could be uh obstacles for an 0:08:20.680 --> 0:08:23.560 electron beam and it would throw everything off if you 0:08:23.720 --> 0:08:27.880 in fact had particles or air inside the microscope. So 0:08:27.880 --> 0:08:31.080 it needs to be a vacuum. The really important element, 0:08:31.200 --> 0:08:33.360 actually all of them are really important, but the business 0:08:33.520 --> 0:08:37.320 element of the scanning electron microscope is the electron gun. 0:08:37.960 --> 0:08:41.920 These are devices that produce a beam of electrons. It's 0:08:41.920 --> 0:08:45.400 really not that different from old CRT televisions. Those have 0:08:45.679 --> 0:08:48.840 electron guns that fire electrons at a phosphorus screen to 0:08:49.040 --> 0:08:52.120 create the light that you would see on an old television, 0:08:52.520 --> 0:08:57.160 but in this case, the electron gun creates a beam 0:08:57.200 --> 0:09:01.240 of electrons to scan your sample. The most common version 0:09:01.760 --> 0:09:04.040 of the electron gun that you will find is the 0:09:04.040 --> 0:09:07.800 thermionic gun, which, as the name implies, has to do 0:09:07.840 --> 0:09:12.240 with heat, right, thermal thermionic. So you heat up a filament. 0:09:12.840 --> 0:09:15.400 You typically would use something like tungusten because as a 0:09:15.480 --> 0:09:18.400 very high melting point, you heat it up really, really 0:09:18.400 --> 0:09:20.560 really hot. And when you do that, when you pour 0:09:20.880 --> 0:09:24.600 energy into it, you help it shed electrons. I've talked 0:09:24.600 --> 0:09:28.200 about this before, where pouring energy into an atom means 0:09:28.240 --> 0:09:33.040 that you're energizing those electrons. Electrons typically orbit and atoms 0:09:33.120 --> 0:09:38.000 nucleus in energy shells, and by boosting the energy of 0:09:38.040 --> 0:09:42.960 those electrons, they moved to higher and higher shells outside 0:09:43.080 --> 0:09:46.839 of that nucleus, and if you pour in enough energy, 0:09:46.880 --> 0:09:49.880 you can strip the electron away from the atom entirely. 0:09:50.160 --> 0:09:52.160 So that's what you do with these electron guns. The 0:09:52.840 --> 0:09:56.040 filament heats up to this incredible temperature and starts to 0:09:56.160 --> 0:10:00.200 shed off electrons. And then you aim those electrons at 0:10:00.240 --> 0:10:02.960 a sample. The other type of electron gun, by the way, 0:10:03.040 --> 0:10:06.680 is the field emission gun, that uses strong electrical fields 0:10:06.720 --> 0:10:11.080 to strip electrons away from their associated atoms. Electron guns, 0:10:11.080 --> 0:10:14.680 whether they're thermionic or field emission guns, are located on 0:10:14.679 --> 0:10:18.439 one end or the other of a scanning electron microscope. 0:10:18.480 --> 0:10:20.960 They're either at the very top or at the very bottom. 0:10:21.120 --> 0:10:24.120 Either way, they're doing the same thing. The lenses in 0:10:24.480 --> 0:10:29.080 a scanning electron microscope are not optical lenses. They're not 0:10:29.559 --> 0:10:34.240 ground glass lenses. The lenses in the scanning electron microscope 0:10:34.240 --> 0:10:39.280 are actually magnets because magnets can shape the path of electrons. 0:10:39.320 --> 0:10:43.959 Electrons have a charge, so using magnets you can attract 0:10:44.120 --> 0:10:47.720 or repel electrons. This is how particle accelerators like the 0:10:47.920 --> 0:10:51.800 large hadron collider work. They use these powerful electro magnets 0:10:51.840 --> 0:10:56.079 to control the beam of charged particles protons or electrons. 0:10:56.679 --> 0:11:00.240 The scanning electron microscope uses magnets to focus the beam 0:11:00.280 --> 0:11:02.760 of electrons and control them and direct them to where 0:11:02.800 --> 0:11:05.600 they need to go in order to scan a sample. 0:11:06.280 --> 0:11:10.800 The scanning electron microscope also has a sample chamber. That's 0:11:10.800 --> 0:11:14.160 where you actually place the specimen that you are scanning, 0:11:14.679 --> 0:11:17.600 and since we're talking about crazy levels of magnification here, 0:11:18.280 --> 0:11:23.040 you need that sample to be super still. Any movement, 0:11:23.120 --> 0:11:26.600 any vibration is going to be magnified dramatically and it's 0:11:26.640 --> 0:11:29.800 going to corrupt your results. So you want it to 0:11:29.840 --> 0:11:33.960 be very stable, and typically that means insulating it against 0:11:34.040 --> 0:11:36.640 all vibrations as much as you can. So if you 0:11:36.679 --> 0:11:39.079 were to go to visit like a forensics lab, and 0:11:39.160 --> 0:11:42.280 let's say it's a huge forensics lab, maybe it's an academy, 0:11:42.320 --> 0:11:45.360 and it's got multiple floors, chances are you're going to 0:11:45.440 --> 0:11:49.680 find the scanning electron microscopes on the ground floor, because 0:11:49.840 --> 0:11:53.280 going up more than just the ground floor could potentially 0:11:53.320 --> 0:11:57.480 introduce vibrations to your sample chamber and that would throw 0:11:57.520 --> 0:12:02.120 off your results. The scanning electron microscope also has detectors. 0:12:02.400 --> 0:12:05.520 Right you're you're blasting a sample with electrons, you have 0:12:05.600 --> 0:12:07.880 to have detectors to pick up the response of that, 0:12:08.400 --> 0:12:12.400 and those detectors include stuff like secondary electron detectors. Those 0:12:12.440 --> 0:12:16.960 are detectors that can actually register electrons from the sample itself. So, 0:12:17.000 --> 0:12:20.120 in other words, you're bombarding the sample with electrons from 0:12:20.120 --> 0:12:24.559 your electron beam. Sometimes that dislodges electrons from the surface 0:12:24.800 --> 0:12:28.840 of the outer surface of the sample, so the secondary 0:12:28.840 --> 0:12:32.559 electron detectors can pick those up. But other detectors will 0:12:32.600 --> 0:12:36.920 include back scatter detectors or X ray detectors. So when 0:12:37.040 --> 0:12:40.720 you are scanning a specimen, the electron beam moves over 0:12:40.760 --> 0:12:43.680 the surface of the object, and to do that, the 0:12:43.760 --> 0:12:47.880 scanning electron microscope uses what are called scanning coils. These 0:12:47.880 --> 0:12:52.079 are magnetic field generators that use fluctuating voltage to create 0:12:52.160 --> 0:12:56.120 the magnetic field, and the scanning electron microscope uses that 0:12:56.200 --> 0:13:00.080 to manipulate the electron beam. The coils direct the beam 0:13:00.120 --> 0:13:03.319 across the specimen in a very tight grid like pattern, 0:13:03.920 --> 0:13:06.199 so up and down, left and right, to get every 0:13:06.200 --> 0:13:11.559 single point on the surface of that specimen. That does 0:13:11.640 --> 0:13:15.160 dislodge electrons from the surface of the specimen in unique patterns, 0:13:15.400 --> 0:13:19.719 so the secondary detector attracts those scattered electrons and then 0:13:19.800 --> 0:13:23.640 registers those electrons as different levels of brightness on a monitor. 0:13:23.960 --> 0:13:26.320 So the intensity of the brightness that you see in 0:13:26.360 --> 0:13:29.880 the image will correspond with the number of electrons that 0:13:29.960 --> 0:13:34.080 hit the detector. The detector quote unquote knows where secondary 0:13:34.080 --> 0:13:37.880 electrons come from based upon the scanning beam's position, and 0:13:37.960 --> 0:13:40.400 this can be shown in an optical image on a 0:13:40.520 --> 0:13:44.760 video display. So think of for for the purposes of visualization, 0:13:44.800 --> 0:13:48.920 imagine a laser beam it's hitting a single point on 0:13:50.440 --> 0:13:53.320 a piece of cloth, let's say, And then imagine that 0:13:53.400 --> 0:13:57.360 you have a sensor that can pick up when electrons 0:13:57.400 --> 0:14:01.040 are being shot off by this piece of off. So 0:14:01.080 --> 0:14:03.520 we're thinking of a laser beam as that's the electron beam. 0:14:03.559 --> 0:14:06.240 We're just imagining it as a laser beam. You move 0:14:06.360 --> 0:14:09.640 the laser beam across the sample, and the detector is 0:14:09.720 --> 0:14:14.600 constantly picking up these electrons as they are shot off 0:14:14.600 --> 0:14:18.480 by the sample. And because this is all happening at 0:14:18.520 --> 0:14:21.040 essentially the speed of light, I mean, we're talking super fast, 0:14:21.480 --> 0:14:23.880 you know where those electrons are coming from, because you 0:14:23.920 --> 0:14:26.200 know what part of the sample the beam has just 0:14:26.320 --> 0:14:30.320 made contact with. And that ends up being transmitted to 0:14:30.520 --> 0:14:34.960 a computer system that interprets that and plots it as 0:14:35.360 --> 0:14:39.360 pixels points of light on the monitor, and then you 0:14:39.440 --> 0:14:43.359 get the computer image of what the scanning electron microscope 0:14:43.400 --> 0:14:49.080 just scanned. It's pretty darn cool. Backscattered electrons are those 0:14:49.160 --> 0:14:51.840 from the beam that reflect off the surface of the 0:14:51.880 --> 0:14:54.560 specimen and a detector can pick up those as well, 0:14:54.600 --> 0:14:58.160 and in a similar way constructive image. So backscatter. Those 0:14:58.200 --> 0:15:02.440 are electrons that came from the electron beam, not we're 0:15:02.640 --> 0:15:05.760 shed by the sample. And then the X ray detectors 0:15:05.760 --> 0:15:08.280 pick up X rays that would be emitted from underneath 0:15:08.280 --> 0:15:11.040 the specimen, and the beam scans the entirety of the 0:15:11.040 --> 0:15:13.720 specimen and the detector's data is used to construct the 0:15:13.760 --> 0:15:18.120 corresponding image. And that's how scanning electron microscopes work if 0:15:18.160 --> 0:15:21.440 you really want to dive more into that technology, because 0:15:21.520 --> 0:15:24.920 I realized again without visual aids it gets a little 0:15:25.000 --> 0:15:29.080 challenging to understand. There's a great article on how stuff 0:15:29.080 --> 0:15:32.640 works about how scanning electron microscopes work. Now, I'm gonna 0:15:32.680 --> 0:15:34.440 take a quick break, and when I come back, we're 0:15:34.480 --> 0:15:37.600 gonna look at some of the other cool technology used 0:15:37.600 --> 0:15:48.320 in forensic science. Now, in the last episode, I talked 0:15:48.320 --> 0:15:52.680 about ballistics and measuring stuff like bullet holes to determine 0:15:52.680 --> 0:15:55.960 the angle and direction of firearm was pointed before firing. 0:15:56.200 --> 0:15:58.440 And in the old days you do stuff like tape 0:15:58.440 --> 0:16:01.520 measures to figure all that out, you know, take physical measurements, 0:16:01.520 --> 0:16:05.280 but today you typically would use laser scanners, they can 0:16:05.280 --> 0:16:08.680 give you much more precise information. A laser scanner depends 0:16:09.320 --> 0:16:13.480 largely on the time of flight method. That's pretty much 0:16:13.560 --> 0:16:17.560 similar to sonar and radar or speed guns that that 0:16:17.760 --> 0:16:21.040 police use to detect the speed of a vehicle. The 0:16:21.040 --> 0:16:24.600 whole idea is what what amount of time does it 0:16:24.680 --> 0:16:27.520 take for a laser beam to travel from in the 0:16:27.560 --> 0:16:31.760 mirror to a sensor. Right, So by knowing the amount 0:16:31.800 --> 0:16:36.400 of time between when a pulse of lasers left a 0:16:36.480 --> 0:16:39.280 laser and when they were picked up by a sensor, 0:16:39.320 --> 0:16:41.880 you can know the distance it traveled. Because it's traveling 0:16:41.880 --> 0:16:44.160 at the speed of light. That's a constant. You can 0:16:44.280 --> 0:16:47.200 use that constant and then work backwards and determine how 0:16:47.280 --> 0:16:50.960 far did this laser beam travel. With laser scanners, you're 0:16:50.960 --> 0:16:54.400 talking about a detector built into the scanner itself, right, 0:16:54.840 --> 0:16:56.840 So they go. You've got an a mitter and a 0:16:56.880 --> 0:16:58.880 scanner and they're next to each other, and then you 0:16:58.960 --> 0:17:02.800 take half the distance that you calculate. Because the beam 0:17:02.880 --> 0:17:06.760 travels out, it hits an object, it travels back and 0:17:06.800 --> 0:17:09.359 gets picked up by the sensor, So that means the 0:17:09.480 --> 0:17:13.720 laser has traveled twice the distance between the point of 0:17:13.720 --> 0:17:17.720 the laser and the the point of contact. So you 0:17:17.760 --> 0:17:20.080 just take half of that that will tell you the distance. Right. 0:17:20.359 --> 0:17:23.600 So you use these laser scanners uh the time of 0:17:23.640 --> 0:17:26.560 flight scanners, and you move them in a grid fashion 0:17:26.600 --> 0:17:30.520 to capture all points of a scanned specimen, and then 0:17:30.560 --> 0:17:32.800 you get this this collection of data points that tells 0:17:32.840 --> 0:17:37.360 you how far away the various parts of a specimen 0:17:37.400 --> 0:17:42.240 were compared to the origin spot of the laser scanner. 0:17:42.760 --> 0:17:45.480 That would allow you to then plot that information in 0:17:45.520 --> 0:17:49.439 a computer and get a real good read on the 0:17:49.600 --> 0:17:53.080 specifics of whatever it was you were scanning. At three 0:17:53.160 --> 0:17:56.679 D dash forensic dot com, there's a description of this 0:17:56.720 --> 0:18:01.600 technology used to investigate a shooting crime to have then Vallejo, California. 0:18:01.920 --> 0:18:06.480 This one took place in there was a couple who 0:18:06.480 --> 0:18:10.399 were in a car that was outside of a home 0:18:10.600 --> 0:18:17.080 in California. An argument broke out, presumably between the couple 0:18:17.200 --> 0:18:20.480 and maybe with someone else as well who was outside 0:18:20.520 --> 0:18:22.639 the car on a porch in front of the house. 0:18:23.480 --> 0:18:27.080 That person on that porch fired an a K forty 0:18:27.200 --> 0:18:31.600 seven at the vehicle. One of the bullets struck and 0:18:31.760 --> 0:18:35.840 killed the driver of that vehicle, but the person who 0:18:35.880 --> 0:18:39.680 shot the a K forty seven later claimed that the 0:18:39.760 --> 0:18:43.760 passenger of this car had a gun and the passenger 0:18:44.000 --> 0:18:46.720 was threatening the person who was standing on the porch. 0:18:47.000 --> 0:18:51.160 So in California, there is something called the provocative act doctrine, 0:18:51.240 --> 0:18:55.920 which states that if someone incites a killing, if they 0:18:56.080 --> 0:18:59.320 escalate a situation and then a killing occurs because of 0:18:59.320 --> 0:19:03.639 that escalator, that person can be charged with murder. So 0:19:03.680 --> 0:19:07.119 the passenger in this car could be charged with the 0:19:07.240 --> 0:19:10.720 murder of the driver of that car because of this 0:19:10.960 --> 0:19:14.440 provocative act. Even though the passenger in the car wasn't 0:19:14.440 --> 0:19:17.040 the one who fired the gun, the argument would be 0:19:17.040 --> 0:19:21.399 because of the passenger's actions, the driver died, so the 0:19:21.440 --> 0:19:25.159 person charged is not the one who actually did the killing, 0:19:25.640 --> 0:19:29.600 but incited the killing to happen. So the prosecution is 0:19:29.720 --> 0:19:34.960 arguing the passengers actions lead to the death of this driver. 0:19:35.840 --> 0:19:37.760 And at the heart of the issue was whether the 0:19:37.760 --> 0:19:41.639 passenger actually did possess a gun and either threatened or 0:19:41.680 --> 0:19:44.359 perhaps even fired it at the person who was on 0:19:44.400 --> 0:19:48.840 the porch. The shooter who stood on that porch fired 0:19:48.880 --> 0:19:52.000 an a K forty seven in full auto mode, which 0:19:52.080 --> 0:19:54.720 means you just hold down the trigger and it will 0:19:54.800 --> 0:19:56.679 keep firing until you let go of the trigger, You're 0:19:56.680 --> 0:20:00.280 out of bullets. Investigators were brought in to answer quite is, 0:20:00.359 --> 0:20:02.639 like where was the car when it was struck by 0:20:02.640 --> 0:20:05.480 the two bullets? What is the line of sight from 0:20:05.520 --> 0:20:08.639 the porch of the house to the position of the car. 0:20:08.680 --> 0:20:10.640 If you assume the height of the person on the 0:20:10.680 --> 0:20:13.879 porches about five ft eight inches, that was the height 0:20:13.960 --> 0:20:16.680 of the shooter. What is the line of sight from 0:20:16.720 --> 0:20:20.080 the front passenger position to the porch, Because if the 0:20:20.080 --> 0:20:23.520 person in the passenger seat was actually threatening the person 0:20:23.600 --> 0:20:25.879 on the porch, they would have to be able to 0:20:25.920 --> 0:20:29.560 see that person. Was the vehicle in motion? If so, 0:20:29.600 --> 0:20:33.160 how fast was it going? And could the investigators determine 0:20:33.160 --> 0:20:35.800 the order of the two bullets that struck the car? 0:20:35.880 --> 0:20:39.359 Which one was first? The three D laser scan that 0:20:39.440 --> 0:20:43.480 the investigators used, uh, they made one of the bullet holes, 0:20:43.560 --> 0:20:45.480 they did of the car, the porch. They actually scanned 0:20:45.480 --> 0:20:47.840 the whole area, but they were looking at the bullet 0:20:47.840 --> 0:20:50.840 holes first, and that indicated that the two bullets that 0:20:50.880 --> 0:20:54.919 were both shot from the same angle, which indicated that 0:20:54.960 --> 0:20:57.680 the shooters stood in the same spot while firing the shots. 0:20:58.280 --> 0:21:01.800 But there were there was a distance between bullet hole 0:21:01.880 --> 0:21:04.960 number one and bullet hole number two, and that distance 0:21:05.240 --> 0:21:08.600 would mean that the car must have moved two point 0:21:08.680 --> 0:21:12.120 seven feet between those two shots. And the reason they 0:21:12.119 --> 0:21:14.760 realized that the car was the one that moved and 0:21:14.840 --> 0:21:17.240 not the person was because the a K forty seven 0:21:17.280 --> 0:21:20.720 was fired in full auto mode. The time between two 0:21:20.720 --> 0:21:24.760 shots from a cold start would be about one tenth 0:21:24.840 --> 0:21:29.200 of a second, which means the car must have moved 0:21:30.080 --> 0:21:34.040 to get two point seven feet further in one tenth 0:21:34.040 --> 0:21:36.479 of a second. That's way too fast for a person 0:21:36.520 --> 0:21:38.840 to have moved and been able to fire this gun, 0:21:39.320 --> 0:21:41.600 and it would mean that the car was moving at 0:21:41.600 --> 0:21:44.199 around a little less than twenty miles per hour. The 0:21:44.280 --> 0:21:48.159 investigators ended up conducting thorough laser scans not just in 0:21:48.200 --> 0:21:50.320 the vehicle, but the whole area where the crime occurred, 0:21:50.640 --> 0:21:53.200 and at the heart of the issue was conflicting testimony. 0:21:53.240 --> 0:21:56.760 Did the passenger have a gun? Was the passenger threatening 0:21:56.840 --> 0:21:59.879 or actively shooting the person on the porch? And based 0:21:59.880 --> 0:22:03.720 on the scans and simulations, the jury found the evidence 0:22:03.760 --> 0:22:06.679 did not support the shooters claim that the passenger was 0:22:06.720 --> 0:22:09.760 threatening the shooter with a gun, and so the charges 0:22:09.880 --> 0:22:15.239 of murder against the passenger were dismissed. So that's kind 0:22:15.240 --> 0:22:18.240 of an interesting way of using laser scanners. It's a 0:22:18.280 --> 0:22:21.600 pretty fascinating discussion. And again, if you go to that 0:22:21.680 --> 0:22:25.520 website three D dash forensic dot com, you can find 0:22:25.560 --> 0:22:28.080 the whole case study written up and in greater detail 0:22:28.160 --> 0:22:31.560 and learn more about it. So let's say let's change 0:22:32.080 --> 0:22:33.720 gears a little bit. Let's say you go to a 0:22:33.760 --> 0:22:38.720 crime scene and there's broken glass everywhere, and the cops 0:22:38.920 --> 0:22:41.919 have a suspect and custody, and a close examination of 0:22:41.960 --> 0:22:45.639 the suspect's clothing revealed that there were some glass particles 0:22:45.680 --> 0:22:48.480 that were attached to that clothing. They were they were 0:22:48.880 --> 0:22:53.120 just stuck on there. But the particles are really small, 0:22:53.280 --> 0:22:56.919 and it's not obvious that they come from the crime scene. 0:22:56.960 --> 0:22:59.680 They might be unrelated. So if you've got really small 0:22:59.720 --> 0:23:02.040 glass particles, they're so small that you can't just you know, 0:23:02.119 --> 0:23:05.439 piece them together, how can you determine whether or not 0:23:05.640 --> 0:23:08.720 they came from the crime scene. Well, you could call 0:23:08.760 --> 0:23:13.600 in the laser ablation inductively coupled plasma mass spectrometry device. 0:23:14.440 --> 0:23:18.120 It's also known as the l A I C p MS. 0:23:18.160 --> 0:23:20.640 One of those cases where the acronym is almost as 0:23:20.640 --> 0:23:23.080 clunky as the full name. It sounds like something out 0:23:23.080 --> 0:23:26.240 of Ghostbusters, doesn't it. But this is a Once you 0:23:26.240 --> 0:23:28.200 break it down into its component parts, it's a lot 0:23:28.240 --> 0:23:31.800 easier to understand because when you hear laser ablation inductively 0:23:31.840 --> 0:23:36.400 coupled plasma mass spectrometry, that seems like it would be insane, 0:23:36.440 --> 0:23:38.000 but it actually makes a lot more sense when you 0:23:38.000 --> 0:23:41.000 break it down. So first, let's talk about laser ablation. 0:23:41.160 --> 0:23:43.600 This is where you use a laser beam that is 0:23:43.800 --> 0:23:46.960 of a particular strength so that when you move it 0:23:47.000 --> 0:23:53.800 across a sample surface, it generates fine particles. Through laser ablation, essentially, 0:23:53.840 --> 0:23:57.720 you're shaving off particles from the sample. You gather these 0:23:57.760 --> 0:24:01.679 particles and they go into a chamber where an inductively 0:24:01.760 --> 0:24:08.320 coupled plasma instrument otherwise known as a plasma torch ionizes 0:24:08.359 --> 0:24:12.280 the particles. Once again, you uh impart a lot of 0:24:12.359 --> 0:24:16.840 energy to the particles, so it ends up ionizing them. 0:24:16.880 --> 0:24:20.640 It sheds electrons, it becomes charged, and then you put 0:24:20.680 --> 0:24:26.680 it through a spectrometer. The spectrometer separates the ions using filters, 0:24:26.720 --> 0:24:30.400 which aren't physical filters. It's not like a mesh or something. 0:24:30.880 --> 0:24:34.040