Tool-Mark Analysis (Wood)
Definition
Examination of surface marks left by cutting, planing, or shaping tools to identify the tool type, size, and individual characteristics of the blade. Nicks, set irregularities, and pitch angle all transfer from tool to wood and can link a piece of wood to a specific machine or hand tool.
- Examines
- Marks from cutting, planing, or shaping tools on wood
- Identifies
- Tool type, size, and individual blade characteristics
- Transferring features
- Nicks, set irregularities, pitch angle
- Notable case
- Lindbergh kidnapping ladder evidence
Common questions
How did tool-mark analysis on wood contribute to the Lindbergh case?+
Wood technologist Arthur Koehler matched distinctive plane marks on the kidnap ladder's rails to a dull, nicked hand plane found among Bruno Hauptmann's tools in his garage, and separately traced one rail's grain and nail-hole pattern to a missing floorboard in Hauptmann's attic, together tying the ladder's construction to his home.
Why do wood tool marks preserve individual tool characteristics well?+
Wood is a relatively soft, consistent medium compared to metal, so a blade's minute nicks and wear pattern imprint cleanly into the cut surface, and the mark tends to survive well because wood does not spring back or self-heal the way some other materials do.
Can wood tool-mark evidence be defeated by re-cutting or sanding the surface?+
Yes, sanding or making a fresh cut removes the original striation pattern, so timing and preservation of the wood surface as found at the scene are important, since any post-crime alteration to the cut edge can eliminate the comparison evidence.
Related terms
- Crossgrain
- A condition in which the wood fibres run at an angle to the long axis of the piece. In Rail 16, Koehler...
- Grain Matching
- The physical comparison of growth-ring pattern and fibre direction at a fracture or cut surface to an adjacent piece of wood. Because...
- Plane Mark
- A surface trace left by a hand or machine plane, showing the arc of the blade stroke and any irregularities such as...
- Rail 16
- Koehler's designation for the left side rail of the bottom section of the Lindbergh ladder. The rail that was matched by grain,...
- Supply Chain Tracing
- In Koehler's investigation, the process of tracking the ladder lumber from the sawmill of origin through the distribution network to the retail...