Abstract
This paper's subject is ballistics, a method used in forensic science during crime scene analysis. For this project, six bullet shell casings will be analyzed for defining characteristics to be compared against three unknown fired shell casings to identify the three unknowns and correlate them to a crime scene being investigated. Six 9mm fired shell casings were supplied for the experiment, and all of their manufacturers were identified, including the pistols the bullets were fired from. Once all manufacturers were logged, the shell casings were examined under a microscope to identify defining characteristics, such as the impact point from the firing pin and scorch marks left on the shell casings. Once all defining traits are logged for each shell casing and grouped by manufacturer, they will be compared to the three unknown shells (not yet provided for my experiment). The three unknowns will undergo the same series of examinations to identify specific traits before finally being compared to known examples and identifying the manufacturer of bullets and weapons.
Ballistic Analysis
Background Information
The basics of what happens when a gun is fired can be described as such: when the trigger is pulled, a mechanism known as a firing pin is activated and projected forward towards a bullet loaded into the gun’s chamber. The purpose of the firing pin is to strike the back of the bullet’s shell casing on a particular spot, called the percussion cap. When the firing pin strikes the percussion cap, the black powder inside the shell casing is ignited and expells the bullet down the gun’s barrel. What makes this process important for forensic scientists is that when this procedure is carried out within microseconds, there are a couple of very important, often overlooked, outcomes which are explained in the article “Specificity of characteristic marks on cartridge cases from 3070 consecutive firings of a Chinese Norinco QSZ-92 9 mm Pistol.” Feng explains, “Every firearm bears its own fingerprint. The manufacturing process leaves unique signatures on the ejector, firing pin, breech face (BF), extractor, and other components on each firearm. During the firing and ejection processes, these signatures produce several marks on cartridge cases that can be used for comparison and case gun matching. The firing pin and BF marks become the specificity of the individual marks on cartridge cases” (Feng et al., 2019 P. 2). The markings that are made on shell casings can be viewed as particular characteristics that can be replicated when firing a similar bullet, from the same manufacturer, from the same weapon that was used, in this case, in a crime. Once these specific traits are identified and compared, it can be the equivalent of finding someone’s fingerprints on a murder weapon and can be used to accurately place a specific weapon in a specific investigation. With that established, this research question can be defined as: with careful analysis, can class characteristics on a fired cartridge casing be significant enough to identify a specific gun that fired it based on my findings and research? After careful and thorough analysis, there will be significant characteristics on the spent casing that will allow them to be matched to casing fired from known guns, thereby allowing the researcher to identify the gun that fired the casing.
Variable Table:
Procedure
This project will examine and try to identify specific traits of fired shell casings of unknown origins. Once all critical, relevant information has been examined and gathered from the unknown samples, they will be compared against the six known examples provided for this experiment. This will be done by closely examining the spent shells underneath a microscope to catalog images of the specific shapes pressed into the percussion caps made by the firing pin. In addition to the firing pin marks, the shells will also be examined for unique scorch marks from the breach face and other components from the gun that fired them. Once a match is identified, a conclusion will be drawn in which evidence will be used for determining which casing is tied to which weapon and the crime scene correlated with it.
Results
Results to be determined.
Discussion
As I am still waiting to receive the three unknown samples, this experiment is currently unfinished. Although the six known samples have been examined, the results are fascinating. Being able to see how each shell casing reacts to such a violent process (a gun being fired), it is becoming clear to see how the specific traits inflicted on the spent shell casings can be viewed as a type of “fingerprint.”
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