Please enable JavaScript.
Coggle requires JavaScript to display documents.
Cartridge and Shotshell Examination (Identification Process (Pattern…
Cartridge and Shotshell Examination
Identification
Developments - Includes new techniques and technology used for firearm identification
Prerequisites for Examination - Before examining a firearm, examiners must follow laboratory policies, document, ensure the use of proper equipment, and include test standards
Individual Characteristics - Include unique impressions made by the firing pin, breech face, chamber, etc. by a particular firearm
Equipment - Include a comparison microscope, range facilities, proper ammunition, stereomicroscopes, imaging equipment
Evidentiary Value - Since a firearm can produce the same types of impression on fired ammunition, examiners are able to identify if a cartridge case had come from a particular firearm
Identification Process
Pattern Identification - Involve comparing two pieces of evidence and determining whether or not the impressions hace a common origin
Consecutive Matching Striae - A process in which the microscopic marks on ammunition are compared
Physical Characteristics - Include class, individual, and subclass characteristics
AFTE Theory of Identification - The three principles of the theory include (1) the ability to establish a common origin based on unique striations. (2) The ability to duplicate the striations (3) Interpretation is subjective and relies on the experience of the examiner
Possible Toolmarks - Can include marks made by the firing pin, breech face, primer, chamber, extractor, ejector, anvil, etc.
Sufficient Agreement and Best Known Nonmatch - Determining a match or nonmatch depends on the examiner's experience and their ability to recognize patterns
AFTRE Range of Conclusions
Inconclusive - Occurs when there is a mix between agreeing that there is a match and disagreement
Elimination - A complete disagreement on the whether or not the class and individual characteristic are considered a match
Identification - The ability to recognize a match based off of patterns
Unsuitable - Occurs when cartridge cases are of no use for comparison
Fired Case Examination
Firearms Without Related Evidence - A process in which the examiner determines whether the firearm is capable of producing particular markings on a cartrdge case
Firearms with Related Evidence - Involves looking the unique markings and dertermining what could have produced such patterns
Microscopic Comparison - Include calibrating the microscope, setting the proper magnification as well as the proper lighting
Evidence without Related Firearm - Involves determining which firearm may have produced the unique striations on the cartridge case
Microscopic Procedure - Include reviewing protocols, completing the required documentation, following safety protocols, determining the presence of trace evidence, fingerprints and whether or not more tests/examinations are needed
Examination Challenges - Include wrong interchanging of the cartridge, issues with the cartridge cases as well as the firearm
Examination of Unfired Ammunition - although most of the common firing patterns are not presence, an examiner can still identify other markings made including extractor, ejector and magazine
Case Linkage - Many cases that were unsolved and had unfound firearms were typically kept in laboratories for comparing with more recent cases to try and determine a link, if any
Dillon, H. John. “Module 09 :: Cartridge and Shotshell Examination” Firearm Examiner Training, projects.nfstc.org/firearms/.