Identification Techniques Used for Firearms, Toolmarks, and Other Impressions
Since the early 20th century, the practice of firearm and toolmark identification or comparison has been a crucial factor in forensic science. Agencies such as the FBI have introduced a standard operating procedure which helps to identify weapons and toolmarks. There are certain criteria that must be met to be considered a match. These criteria include multi-level matching of the items brought from the scene of a crime with the test specimens. (http://www.fbi.gov/about-us/lab/forensic-science-communications/fsc/july2009/review/2009_07_review01.htm).
“The examination process typically begins when an examiner receives a suspect firearm, along with bullets (the projectiles) and spent cartridge cases recovered from a crime scene.” (http://www.fbi.gov/about-us/lab/forensic-science-communications/fsc/july2009/review/2009_07_review01.htm). Next, the suspect weapon is test-fired into a tank of water or a cotton filled recovery box so that bullets, together with their cartridge casings (which serve as a control) may be analyzed. The test-fired bullets are then examined via comparison microscope. This will confirm or rule out a relationship between the control and the bullets retrieved from a crime scene.
According to the Firearms Tutorial, there are three possible results of comparison identification. Test-fired bullets and those retrieved from a crime scene may be related to the same weapon; may not be related to the same weapon; or not even be likened via this kind of test. It is not recommended that forensic examiners make assumptions founded primarily from test firing. Analyzing an image of the bullets and casings may be used to compare and even identify the weapon from which the bullet was fired. (http://library.med.utah.edu/WebPath/TUTORIAL/GUNS/GUNINTRO.html).
Additionally, standards have been established for consecutively matching striae, or CMS. Bullets contain striations as a result of being imprinted with markings on its journey through the barrel of
“The examination process typically begins when an examiner receives a suspect firearm, along with bullets (the projectiles) and spent cartridge cases recovered from a crime scene.” (http://www.fbi.gov/about-us/lab/forensic-science-communications/fsc/july2009/review/2009_07_review01.htm). Next, the suspect weapon is test-fired into a tank of water or a cotton filled recovery box so that bullets, together with their cartridge casings (which serve as a control) may be analyzed. The test-fired bullets are then examined via comparison microscope. This will confirm or rule out a relationship between the control and the bullets retrieved from a crime scene.
According to the Firearms Tutorial, there are three possible results of comparison identification. Test-fired bullets and those retrieved from a crime scene may be related to the same weapon; may not be related to the same weapon; or not even be likened via this kind of test. It is not recommended that forensic examiners make assumptions founded primarily from test firing. Analyzing an image of the bullets and casings may be used to compare and even identify the weapon from which the bullet was fired. (http://library.med.utah.edu/WebPath/TUTORIAL/GUNS/GUNINTRO.html).
Additionally, standards have been established for consecutively matching striae, or CMS. Bullets contain striations as a result of being imprinted with markings on its journey through the barrel of
Cited: Bangalor, S. et al. Firearms Tutorial. Retrieved from http://library.med.utah.edu/WebPath/TUTORIAL/GUNS/GUNINTRO.html Bunch, S.G., Giroux, B.N., Murphy, D.P., Smith, E.D. (2009). Is a Match Really a Match? A Primer on the Procedures and Validity of Firearm and Toolmark Identification. Forensic Science Communications. July 2009 - Volume 11 - Number 3. Retrieved from http://www.fbi.gov/about-us/lab/forensic-science-communications/fsc/july2009/review/2009_07_review01.htm Saferstein, R. (2009). Forensic Science: From the crime scene to the crime lab. Upper Saddle River, NJ. Pearson Prentice Hall.