Forensic Tool Impressions

Tool Mark

Any impression, scratch, or abrasion made when contact occurs between a tool and an object

Indentation Mark

An impression made when a tool is pressed against a softer surface.

Abrasion Mark

A mark made when surfaces slide across each other, leaving scratches.

Cutting Mark

A mark created along the edge of a surface as it is cut.

What type of evidence considered

Circumstantial Evidence

How can tool marks link a suspect to a crime?

Tools leave unique surface characteristics that can match marks found at a crime scene

Why are tool marks considered circumstantial evidence?

They can suggest a suspect’s involvement but do not directly prove they committed the crime.

What factors affect tool mark identification?

Repeated use, oxidation (rusting), and uneven sharpening create unique characteristics.

Steps for Documenting Tool-Mark Evidence

Photograph tool marks

Document details of the evidence

Cast impressions of the marks

Collect and preserve evidence properly

Why should crime-scene tool marks and suspect tools not be fitted together?

It could alter or damage the evidence, compromising its integrity.

What technology is used in tool-mark analysis?

Comparison Microscopes - Compare tool marks side by side.

3D Characterization Methods - Analyze the depth and shape of tool marks.

Ames Laboratory Database - Stores tool-mark images for comparison.

How can serial numbers on tools help an investigation?

They can be traced to the store where the tool was purchased.

How is tool-mark evidence presented in court?

Original tools and marks, casts, and magnified images are used to demonstrate matches.

Why are organizations like SWGs and OSAC important?

They establish guidelines to improve the reliability of forensic tool-mark analysis.