Print Mark Evidence with airSlate SignNow

Print mark evidence

hi my name is John and I'm a forensic scientist at the BCI lab I work with firearms and toolmarks with firearms we examine all types of guns we examine fired cartridge cases and fired bullets like these and try to link them to a particular firearm we do that by looking at the small markings that are left on bullets and cartridge cases under a microscope we also examine tools that are used in crimes that's what we're doing in Bob's case today remember Bob's barn looked like it had been broken into when agents were gathering some clues at want to bys house they noticed this crowbar in the back of his truck so today what we're trying to figure out is whether this crowbar was used to make the mark found on the barn door if you remember the agents out in the field made a cast or an impression of that mark and that's what this red thing is here so the first thing that I would do is make an impression of the unique markings from this tool and I do that using a material called lead we use a ledge sheet and make marks of those imperfections on the blade so what I would do is drag the blade across the lead and it'll leave those marks so then what we would do is make a cast using that same red material to see if we can get those marks that come up on that material and then we can bring them over to the microscope so I do that by spreading a little bit of this red material here and once we have some on there we can spread it out and it'll harden and we can then bring that cast over to the microscope it takes about a minute to dry and then we're ready to go so now we're at the microscope the first thing we're gonna do is take that cast that we made using the crowbar and peel it off and put it on the left side of the microscope and once we do that we're going to compare that to the cast that was made of the mark that was found on the barn door that was recovered by our agents in the field that's going to go on the right side of the microscope and what we're looking for is a series of lines the marks that are made when that tool scrapes across the metal in this instrument that we use is called a comparison microscope the way it works is you've got one set of eyepieces that we look through and we can look at two different objects side by side at the same time so let's take a look and what I'm looking for is those lines on the left side of the microscope and the right side of the microscope to line up and when they do I can say that the two casts the marks on those casts were made by the same tool and I can see that those marks all line up so what that tells me is that the tool that we found in want to buy struck made the marks that were found at the barn door you