- 01: Introduction
- 02: History
- 03: Propellants, Firearms, and Ammunition Development
- 04: Modern Firearms Manufacture
- 05: Small Arms Ammunition
- 06: Evidence Handling Procedures
- 07: Equipment and Instrumentation
- 08: Examination of Firearms
- 09: Cartridge and Shotshell Examination
- 10: Characterization and Evaluation of Fired Projectiles
- 11: Bullet Comparison and Identification
- 12: Gunshot Residue and Distance Determination
- 13: Toolmark Identification
- 14: Communicating Results
- Resources
Pattern Identification
Home > Cartridge and Shotshell Examination > Identification Process > Pattern Identification
Pattern matching is the process of determining whether or not the details of striated marks or impressions on two objects correspond, such as fired and unfired cartridge cases and shotshell cases. Early forensic scientists and their successors, (including Calvin Goddard, Julian S. Hatcher, Gerald Burrard, J. Howard Mathews) practiced pattern matching. Today, examiners continue to rely on their extensive experience, training, and education to perform the specialized pattern identification represented by toolmark identification.
Microscopic comparison of breech face
marks in the primer area
The examiner compares the class characteristics of the two objects; if all discernable class characteristics correspond, the examiner proceeds to compare the individual characteristics. During the comparison of the individual characteristics, the examiner looks for repetitive marks occurring on both objects in the same location and position. The examiner may test the tool in an effort to re-create the marks for comparison with the evidence marks.
The most difficult aspect of this mental process is the articulation of how an identification can be determined. This process has traditionally been more qualitative than quantitative, and therefore difficult to convey to a jury.
Click here to read more on the quantitative approach of Hatcher's Probability.
What was needed was a structured theoretical basis to assist in
- establishing an identification as to a common source,
- conveying results to a jury,
- justifying results to a jury.
This is a somewhat subjective process performed by the examiner. Pattern identification relies on the experience, training, and education of the examiner. The quality of training is the single most important element of the examiner’s competence and expertise. Long-term hands-on experience is gained from working side-by-side with an experienced examiner in a structured training program.
