Combination Mark
Definition
Both impressed and striated features in the same mark, typical of pry-bar and chisel attacks where the tool first bites into the surface (impressed) and then slides (striated).
- Field
- Tool mark examination
- Composition
- Both impressed and striated features
- Typical tools
- Pry bars, chisels
- Mechanism
- Tool bites in (impressed), then slides (striated)
Common questions
Why does a combination mark give an examiner more information than a pure impressed or striated mark?+
It preserves two independent lines of evidence from a single tool action, the shape and dimensions from the impressed portion and the individual working edge characteristics from the striated portion, which together can strengthen an identification beyond what either alone would support.
How does an examiner decide which part of a combination mark to use for comparison?+
The striated portion, formed as the tool slides under pressure, usually carries the more individualising microscopic detail, so examiners typically prioritise that region for detailed comparison while using the impressed portion to corroborate tool type and approximate dimensions.
Related terms
- AFTE Range of Conclusions
- Association of Firearm and Tool Mark Examiners standard scale: Identification, Inconclusive (A, B, C), Elimination, Unsuitable for examination. The same scale used...
- Class Characteristic
- A feature shared by an entire group of objects (every shoe of one model has the same sole tread; every tire of...
- Impressed Mark
- Also called indented or compression mark. Tool is pressed perpendicularly into the softer surface and reproduces the contour of the tool's working...
- Individual Characteristic
- A characteristic unique to a specific typewriter unit arising from manufacturing variation or service wear; used to identify or eliminate a specific...
- Mikrosil
- Brand-name silicone polymer casting compound (also Microsil, AccuTrans) used to lift a fine-detail negative of a tool mark from the scene without...
- Striated Mark
- Also called scratch, abrasion or scrape mark. Tool slides laterally across the surface and leaves parallel striations from microscopic imperfections on the...
- Subclass Characteristic
- Batch-level feature introduced by manufacturing-tool wear that is shared by a sub-population of tools made in the same production run (a die...
- Toolmark
- The microscopic striations and impressions left on a softer material (a bullet, a cartridge case, a lock body) by contact with a...