Date of Submission

5-2025

Document Type

Thesis

Degree Name

Master of Science in Forensic Science

Department

Forensic Science

Advisor

Virginia M. Maxwell, D. Phil.

Committee Member

Lisa Ragaza, M.S.

Committee Member

Ted Schwartz, M.S.

Keywords

Impressed Toolmarks, Striated Toolmarks, Wood, Relative humidity, Evidence Collection, Distortion

LCSH

Wood, Humidity, Evidence, Criminal

Abstract

Toolmark evidence consists of striated and impressed toolmarks. Striated toolmarks are composed of individualizable striations that are produced to a tool’s surface irregularities when it is scraped against another material. Impressed toolmarks are typically evaluated for valuable class characteristics, such as the size and shape of the mark, which can provide investigators with the type and size tool that was used. At crime scenes, toolmarks are often found around points of entry in wooden doors and window frames. Wood, as relatively unstable substrate, retains impressed toolmarks with little chance of retention of any individualizable characteristics. The hygroscopic properties of wood can cause toolmark’s class characteristics to be distorted or eliminated with any change in relative humidity, such as the change in relative humidity that toolmark evidence undergoes when collected from a crime scene and stored in an evidence storage area. Understanding the changes that occur when toolmark evidence is collected and store could improve methods of collection and inform the evaluation of toolmark evidence. This research investigates how toolmark evidence distorts due to change in relative humidity during the collection and storage process and how factors, such as the change in relative humidity the wood is exposed to the wood species, whether the wood has a coating or how the toolmark is oriented in relation to the grain. Toolmarks were created by a screwdriver, crowbar, and hammer in uncoated, primer and oil-based paint coated, and primer and water-based paint coated white oak, southern yellow pine, eastern white pine and Douglas fir wood. The wood was allowed to acclimate to low, moderate or high humidity conditions, marked, transferred to low humidity conditions, and measured every other day for a month. Toolmarks in wood initially acclimated to moderate humidity conditions exhibited the greatest variation. There were no clear trends in toolmark variation across wood species. Toolmarks in uncoated wood exhibited greater variation than toolmarks in coated wood. Across all toolmarks, the greatest variation was observed in the tangential direction.

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