Impression Mark
Definition
A compression mark made when a tool meets a softer surface with no relative motion. Hammer face on brass, plier jaw crimping a wire, a stamp die on lead.
- Formation
- Compression, no lateral motion
- Contrast
- Striated mark, formed with relative motion
- Examples
- Hammer face on brass, plier jaw on wire
- Comparison basis
- Class and individual tool face characteristics
Common questions
How does an impression mark differ from a striated mark in tool mark analysis?+
An impression mark forms purely from static compression, capturing the tool surface as a two-dimensional imprint, while a striated mark forms when the tool moves laterally across the surface, leaving parallel scratch lines that need different comparison microscopy.
What limits the evidentiary value of an impression mark?+
A soft or deformable surface, multiple overlapping impressions, or partial contact can distort or obscure the tool's individual characteristics, reducing confidence in a comparison to class-level features only.
Related terms
- Class Characteristics
- Features deliberately or systematically imparted to a group of items by design or manufacture, such as the calibre of a bullet, the...
- Dynamic Mark
- A combination of compression and sliding in one contact. The most common real-world tool mark and the hardest to reproduce in test...
- Individual Characteristics
- Surface features on a fired bullet or cartridge case that arise from random or unique events (tool wear, corrosion, service damage) and...
- Striation Mark
- A scratch pattern made when a tool slides across a softer surface. Pry bar dragging across painted wood, blade cut, a screwdriver...
- Test Mark
- A reference mark deliberately made with a suspect tool against a soft medium (lead, clay, aluminium) so it can be compared against...