As a forensic discipline, the essential protocol for firearms identification is the microscopic comparison and potential identification of fired bullets as having been fired from the barrel of the same firearm.
The foundation for this technique is based on the following principles:
- The rifling in the barrel of a firearm bears unique microscopic characteristics due to manufacturing processes, use, and abuse.
- These characteristics mark the bearing surfaces of bullets when fired through the barrel.
- These individual characteristics are reproducible and identifiable with a particular firearm.
Comparison microscopy is used to establish identification and involves one of the following situations:
|Recovered firearm without related evidence
|Obtain test bullets for later comparison by test firing the recovered firearm.
|Recovered firearm with related evidence
|Obtain test bullets from evidence firearm and compare to recovered bullet to determine if the recovered firearm fired the evidence bullet.
|Recovered bullets without related firearm
|Perform intercomparison to determine if recovered bullets are related to a single firearm.
The following preliminary steps should be addressed prior to any of the case comparisons:
- Review laboratory protocols, as needed.
- Complete administrative requirements.
- Chain of custody.
- Marking of evidence.
- Laboratory case identifiers.
- Investigative file identifier.
- Examiner identity.
- Quality assurance.
- Follow laboratory safety protocols.
- Determine the presence of trace evidence and follow laboratory protocol for collection.
Examples of trace evidence include
- soft tissue,
- metal smears,
- Determine if latent fingerprint examinations should be performed prior to toolmark examinations.
- Determine if other examinations (not requested) should be performed. If so, coordinate with the investigator.
Additional Online Courses
- What Every First Responding Officer Should Know About DNA Evidence
- Collecting DNA Evidence at Property Crime Scenes
- DNA – A Prosecutor’s Practice Notebook
- Crime Scene and DNA Basics
- Laboratory Safety Programs
- DNA Amplification
- Population Genetics and Statistics
- Non-STR DNA Markers: SNPs, Y-STRs, LCN and mtDNA
- Firearms Examiner Training
- Forensic DNA Education for Law Enforcement Decisionmakers
- What Every Investigator and Evidence Technician Should Know About DNA Evidence
- Principles of Forensic DNA for Officers of the Court
- Law 101: Legal Guide for the Forensic Expert
- Laboratory Orientation and Testing of Body Fluids and Tissues
- DNA Extraction and Quantitation
- STR Data Analysis and Interpretation
- Communication Skills, Report Writing, and Courtroom Testimony
- Español for Law Enforcement
- Amplified DNA Product Separation for Forensic Analysts