Comparing Cartriges found at the crime scene

In this report we were to study Dan’s bullets to those at a crime scene. We made a diagram to compare the cartridge of Dan’s and the ones that we found at the scene. The results of this comparison were that Dan was innocent by looking at the compared cartridges.

Ballistics is the science that studies movement of objects (bullets etc. ) Guns can be classified as long guns ( two hands), handguns (one hand), firearms, and rifles.  To analyze the ballistic evidence you can look at the markings on the cartridge, a cartridge is a case or shell that holds a bullet, primer powder, and gun powder. This will show the movement of the bullet, different guns will create different markings on the bullets/cartridge.

bullets

As you can see on the picture of the bullets above, they both have grooves, these grooves are from the exiting of the bullet. Each gun will create a different pattern on the bullets. Also, firing pin marks appear on the rim or center of the spent cartridge. Breechblock marks are produced when the cartridge casing slams into the bullet/ammunition.

cartridge.png

 

At our crime scene the ammunition that was found were casings and two bullets that were used. The bullets were used for live ammunition. The same for the casings that were found even though it is not live ammunition now, it was at one time. The caliber of each piece of ammunition was measured in MM. The 12GA is 2.2 mm, 20GA is 2.1mm, 44REM MAG is 1.8mm, 40 S&W is 1.5mm, Super (believe 22 shotgun) is .5mm, and lastly the bullets measured were 1.2mm. Most of the ammunition found came from a shotgun, what we did find is that the bullet that Dan had shot came from a long gun or rifle.

 

I do believe I have some kind of evidence that my gun was used in the crime scene, Dan was shooting the same bullets of that at the crime scene. Dan’s bullet is the on at the bottom and the other two were the ones found at the crime scene. Dan’s bullets seemed as those of a shotgun  a 44 gauge shot gun.

bullets 2

In our head their are two wounds total, one being an exit wound and the other an entrance wound. The reason we can tell which is the entrance wound is if the wound is small and round, usually a pretty clean entrance. We can determine an exit wound of how large the wound is, the reason an exit wound is typically larger is because the bullet will carry parts of the body with it. The more the bullet brings with it the bigger the exit wound.  Down below the fist picture is the entrance wound and the second picture is the exit wound which is about  3mm wide.

Based on the wounds, the gun that was used was a handgun. The reason behind this is a handgun will usually leave a clean wound mark. Also, smaller calibers tend to lodge in the body while larger calibers with pass through. This bullet that was shot was a big enough bullet to pass through the body. While a rifle or shotgun (not a 22 shotgun) the bullets are much larger and the gunpowder inside would leave speckle marks all over the target.

The GSR tells us about how far or how close the shot was from. Since we cannot see any GSR I am assuming that the person who shot this gun was 36 or more inches away from the target.

The approximate angle that the bullet made through the head was at an angle because the shot was made just above the left eye on the temple and came out the back of the head. Meaning that the person who shot this bullet was mostly straight in front of the target but slightly off. This may imply on the situation that the person making this shot was doing this intentionally, trying to kill the victim in one shot.

 

I do not believe that officer Dan was involve in the crime scene because as you can see in the diagram below comparing the two cartridges, the half cartridge on the left side is officer Dan’s and the half cartridge on the right is the cartridge found at the crime scene, after going over everything that I’ve learned, the firing pin marks do not hit the same and there are breechblock marks on officer Dan’s cartridge and nothing on the crime scene cartridge.

diagram bullets.png

What I have learned while studying ballistics and doing this experiment is that studying ballistics is very difficult and tedious work. I learned how to compare cartridges and how to measure the gauge of a gun and how each gun will leave a different pattern on bullets.The next steps in this investigation should be to further examine all of the bullets found.

 

 

Advertisements