Please enable JavaScript.
Coggle requires JavaScript to display documents.
Cartridge and Shotshell Examination John H. Dillon, Jr. “Module 09:…
Cartridge and Shotshell Examination John H. Dillon, Jr. “Module 09: Cartridge and Shotshell Examination.” Firearm Examiner Training, National Forensic Science Technology Center, projects.nfstc.org/firearms/module09/fir_m09.htm.
Identification
Developments: advancements in equipment, digital imaging, and computer hardware have helped to better identify firearms
Prerequisites for Examination: follow laboratory policies, perform documentation, calibrate equipment, identify class characteristics, identify microscopic marks, and obtain test standards
Individual Characteristics: marks on surface caused by cycling and firing mechanisms
Equipment: comparison microscope, range facilities, ammunition, stereomicroscope, and imaging equipment
Evidentiary Value
Fired: identification of cartridge and shotshell cases through firing pin, breech face, and chamber fmarks
Fired and Unfired: identification through extractor, ejection, and other mechanism marks
Identification Process
Pattern Identification: compare class characteristics first- if they all match, then compare individual characteristics to see if they match
Consecutive Matching Striae: criteria set for two and three dimensional toolmarks- don't always have to follow but are more credit
Physical Characteristics: class, subclass, and individual characteristics
AFTE Theory of Identification: three principles
Toolmarks of common origin
Significant agreement
Identification and individualization are subjective
Possible Toolmarks: firing pin impressions, firing pin drag marks, breech face marks, primer shearing marks, chamber marks, extractor marks, ejector marks, anvil marks, ejection port marks, and magazine marks
Sufficient Agreement and Best Known Nonmatch: depends on experience, training, and skills of firearms examiner
Fired Case Examination
Firearms Without Related Evidence: examine test cartridge and/or shotshell cases in order to see if the firearm reliably produces the same microscopic parks
Firearms With Related Evidence: examine questioned and test cartridges to compare them, and if no identification can be made, then examine further to see why they don't match
Microscopic Comparison: calibrate microscope and select proper magnification and lighting for examination
Evidence Without Related Firearm: examine and document all microscopic marks
Microscopic Procedure: document everything, follow protocol, and check for trace evidence, and finger prints before performing your examinations
Examination Challenges
Cartridge Cases
Reloading toolmarks
Manufacture/assembly factors: primers and bunter marks
Firearms
Use of adapters
Substitution of parts: pistol components or revolver cylinders
Modifications: refiling
Manufacturer-related factors: subclass characteristics
Cartridges
Inappropriate interchangeability: can sometimes use more than one cartridge type
Examination of Unfired Ammunition
Examination similar to fired ammunition: look for and compare extractor, ejector, and magazine marks
Worksheets: pretty much the same as fired ammunition documentation, except put that there weren't any chamber, breech face, or firing pin marks
Case Linkage: files kept from unsolved cases in order to possibly link them to others
Computer-based- IBIS
AFTE Range of Conclusions
Inconclusive: some marks match, but can't be identified or eliminated
Elimination: difference in class and/or individual characteristics sufficient to determine difference
Identification: individual and class characteristics match, and it can be proven that the marks weren't made by a different tool
Unsuitable: mutilated cartridges and shotshells that don't have microscopic marks