Home | Glossary | Resources | Help | Contact Us | Course Map
Archival Notice
This is an archive page that is no longer being updated. It may contain outdated information and links may no longer function as originally intended.
Identification Process
A tool is the harder of two objects, which when brought into contact with each other, results in the softer one being marked. This marking is known as a toolmark.
Firearms identification is simply a firearms-related specialized subset of the broader field of toolmark identification.
When the various parts of the mechanism of a firearm come into hard contact with a cartridge case or shotshell case (typically made of a relatively softer metal such as brass), a toolmark can be created.
The cycle of fire includes a number of steps that are common to all firearms:
- Feeding of a cartridge manually or from a magazine
- Chambering of a cartridge
- Locking of the breech or bolt mechanism
- Firing by releasing of the firing pin
- Obturation, specifically, sealing of powder gases forward of the cartridge case or shotshell case by expansion of the cartridge case to fully fill the chamber, as well as by expansion of projectiles or wadding material
- Unlocking of the breech or bolt mechanism
- Extraction of the fired cartridge/shotshell case
- Ejection of the fired cartridge/shotshell case
- Cocking of the firing mechanism
These steps may be performed manually, semiautomatically, or fully automatically. Depending on the design of a firearm, certain steps may be combined.
Review the YouTube Terms of Service and the Google Privacy Policy
Review the YouTube Terms of Service and the Google Privacy Policy
Striated marks occur when there is relative motion between two objects under pressure. Striations are contour variations (generally microscopic) on the surface of an object caused by a combination of force and motion, where the motion is approximately parallel to the plane being marked. Striated toolmarks could also be described as scratch marks, abrasion marks, or friction marks.
Impressed toolmarks (compression marks) occur when a tool is placed against another object and sufficient force is applied to the tool that an impression is made. The class characteristics (size and shape) can indicate the type of tool used to produce the mark. These impressions can also contain individual characteristics of the tool producing the mark.
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