Recovered Firearm Without
All firearms submitted to the laboratory should be test fired and the bullets recovered for the following reasons:
- To determine if the firearm reliably reproduces microscopic marks on test fired bullets that are suitable for comparison purposes
- To allow the examiner to assess the quality of marks produced by the firearm
- To retain physical samples of bullets fired from all firearms entering the laboratory
These bullets are retained for these purposes:
- Comparison with new evidence submissions at a later time
- Entry into digital image reference files
The comparison of test bullets should be performed according to laboratory protocol.
A sample procedure follows:
- Recover test fired bullets from the submitted firearm.
- Mark the test bullets and indicate the sequence in which they were recovered.
- Use a stereomicroscope to determine the presence and quality of microscopic marks on the test bullets prior to examination under the comparison microscope.
- Place one of the test fired bullets on the right stage of the comparison microscope. Attach the nose of the bullet to the mount.
- Adjust the lighting from the rear of the microscope to provide oblique illumination over the bearing surface of the bullet.
- Examine the entire bearing surface of the test bullet using low magnification (10x-20x) to determine the best area of individual characteristics. When such an area is located, leave the right stage in that position.
- Place a second test bullet on the left stage with the nose in the same direction as the bullet on the right stage.
- Rotate the bullet on the left stage looking for the same area of individual characteristics as on the bullet on the right stage. The entire surface of the bullet should be considered. Higher magnifications should be used to verify the correspondence of finer striations.
- If an area of correspondence is found, align the land or groove impressions and rotate both bullets simultaneously. Examine and compare each land impression and each groove impression area from base to nose until it a conclusion can be drawn that there is or is not sufficient agreement for identification.
- These examinations should be made with the bullets in phase. This means that the edges of the land and groove impressions of both bullets align with each other and the relationship of the other land and groove impressions in the viewing area is the same.
- Agreement is sufficient when it exceeds the best level of agreement demonstrated between bullet striations known to have been produced by different barrels (the best known nonmatch).
|During training, firearm examiners must compare test fired bullets to bullets fired through a series of barrels of the same make and model. This serves to inform the student of the striation mark agreement necessary to constitute an identification and to distinguish this from bullets with similar striation marks known to have been fired through different barrels.
- If an identification cannot be made between the test bullets (there is not sufficient agreement), then more test bullets should be fired and compared. If an identification still cannot be made, the examiner may reach the conclusion that the barrel of the firearm in question does not consistently produce sufficient individual marks to warrant an identification.
- If an identification can be made, the area of best agreement or the area with the most obvious striations should be indexed with a permanent marker at the base and nose for later use in comparisons with evidence bullets. Indexing allows an examiner to quickly return to an area of correspondence.
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