Ballistics is one of the older forensic sciences. As far back as the early/mid 1800s, bullets could be matched to a particular caliber of weapon. However, it wasn’t until 1895, after rifling was introduced, that ballistics came into its own. Improvements in microscope photography and the introduction of the electron microscope in the 1970s brought the forensics of guns into the modern era.
However, there are two problems with using ballistic evidence. The first is that some bullets fragment on impact. Forensic scientists need enough fragments to reproduce an image of the bullet. If they don’t have them, the bullet is of little help. The second is that, in order to compare a bullet from a crime scene to a bullet from a particular gun, the lab people need the gun. No gun, no comparison, though the bullet may be matched to other crime scenes through NIBIN/IBIS (National Integrated Ballistic Information Network).
Guns, when recovered, can yield significant information including biologics and fingerprints. I’m guessing that’s why so many murder weapons end up buried or tossed into deep water. 🙂
Other elements of investigation include the trajectory of the bullet, the velocity, if it can be determined, and the presence of gun powder residue, either on the suspect’s hands or near the victim’s wound (we’re already familiar with the term “stippling” from TV, which indicates the gun was in close proximity to the victim when fired.
Recovered suspected weapons are fired into a water tank. The bullet is removed from the tank and compared to any bullets or fragments found at the crime scene. Rifling marks, the lands and grooves, are individual to each gun. There may also be indicators of speed of rotation as the bullet passes through the barrel, and/or marks from the firing pin. Criminals who bench-load their own ammo probably leave tooling marks and individual elements in their gun powder as well.
I was happy to see a show this past year in which a detective explained to a gang member exactly why holding the gun sideways gangsta-style was a bad idea. The kid didn’t listen and the gun ejected the shell into his face. It brings to mind the fact that investigators can tell a lot about the gun and the position of the shooter by where the shell casings end up.
Speaking of shells, we’re also familiar with the term “policing the brass,” which indicates the shooter picked up his spent shells and took them with him. Most shooters don’t take the time, possibly leaving behind prints or other information with the casings themselves. I had some first-hand experience due to an unruly neighbor. My husband and I got a mini-lesson in trajectory and helped locate the casings. Each was picked up with care and stored in evidence. That’s why I own a revolver. (Just kidding . . . about the why, not the revolver.)
This doesn’t just refer to guns, but one thing TV routinely gets wrong is the use of plastic bags for evidence. Most evidence is collected in paper bags. Guns may be put into a paper bag or wrapped in brown paper. Paper preserves the evidence that plastic might easily destroy.
Several great sites exist for writers who want to know more about ballistics and guns in general to create accuracy in their stories. For examples, the NSSF published The Writer’s Guide to Firearms & Ammunition as a pdf download. But my favorite of all time and my go-to for questions is Lee Lofland at The Graveyard Shift. If you are at all interested in writing crime stories, his site should be your first bookmark.
Next week is trace evidence.
Do you find ballistics evidence an interesting part of the story or less so? If not your favorite, do you think it’s because we’re more familiar with it?
Other posts in this series:
Crime Scenes for Writers: Ballistics