How Ballistics Study Changed in Forensic Science
Rebecca: We’ve seen CSI on TV using this technology to catch the bad guys, but real life cops find it just as useful. Hi I'm Rebecca Brayton and welcome to watchmojo.com and today we’re speaking with firearm specialist Andy Boyle to learn more about the integrated ballistics identification system, so why don’t we start by having to tell what is IBIS?
Andy: What is this machine that is use to photograph the markings on bullets and cartridge cases after they have been fired through a gun. They actually end up with a unique pattern of scratch and striations that will repeat from fire arm to fire arm but always unique.
Rebecca: How does the system affect investigations today?
Andy: Traditionally, it is a detective so actually comeback to the farm examine say there was shooting last night. It seems like it was this guy who did it, we got his gun, is this the gun that did it, they might not going to match off with that crime scene but now both of those pieces of evidence are in the system it wont forget and any time later it may come up with the hit and the farm examiner and call and text them up and say remember that crime scene from two months ago that we don’t any for you. The gun was just used again in a bank robbery last night.
Rebecca: Would you be able to show us some of the defining characteristics of a bullet and casing?
Andy: Yep, absolutely, see the cartridge has got four main components you got you bullet the cartridge case itself the primer in the back and gun powder on the inside. During the firing sequence what happens is the firing pin in the fire arm strikes the primer which causes the spark inside. The spark makes it auto burn which builds a pressure and cause the bullet to go down the barrel. The riffle marks inside the barrel that cause the bullet to twist are actually dry to cross the surface of the bullet and so you get this channels these grooves basically that have a unique pattern of strips all the way around all that pressure that push the bullet down at the barrel equals to reaction pushes that cartridge case straight to the breach wall.
And so whatever pattern is on that wall you got to stamp across the surface of the departure case and those are two areas they’re on the bullet as well on the cartridge case and they’re giving you any pattern that will reproduce from shop to shops. The machine we are looking at here is what we call bullet tracks it’s used to do a 3D topographical scan of the markings and the bullets surface. You mount the bullet underneath the sensor and little bit rotating 360 degrees around while the actual sensor is capturing the surface topography. As that light shine across you can even still make out that shard of pattern, it’s doing an index scan right now. So now with the acquisition completed over here what we will do is the cartridge case acquisition on the brush track machine.
So the machine we are looking at here is called brush tracks and it used to photograph the markings on the head of the cartridge case. We’re going to take photographs of the breached face marks on the primer, and we are going to do a close up of the firing pin impression as well and we also going to do a close up of the ejector mark on the side. On this cartridge case you got the silver disc in the back of it. We are going to do some photographs of that silver disc, the primer so we will do that right now, once you got to do now is what we call the full head stamp. Its going to take a series of nine photographs which will then reconstruct into one giant image that’s got the entire head of the cartridge case in one giant photo. So what we are looking at now is a close up of the breached face information. All the striations that were marked on that break face was photographed, we are able to look at them side by side and move the hairline back and forth to see how much is common between the reference exhibit and the test one.
Here is your reference this is the guy that was standard during the coloration and this is the guy that was in the data base that came up the best ventral match and already to the naked eye you already got a lot of similarities here with the one of the shoe marks. Also the striations on the surface you can see what the ring like image that we are looking at. There are some common details between the two. So we are going to look at now is the correlation results with the bullet score, so what I want to do now is see how much combing information there is between these two exhibits by sliding together and also by moving that hairline back and fort. So what the track machines are enabling fire examiners to do now in the crime lab is to scan through a thousands of reference exhibits now, posture section as well that are just numbers that we would never be possible and it is really given a mutual to create links and crimes and get criminals off the street.
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