The cutting edge - Micro-CT for quantitative toolmark analysis of sharp force trauma to bone.

Area of Science:

• Forensic Science
• Materials Science
• Biomechanical Engineering

Background:

• Toolmark analysis, particularly for knives, is an emerging forensic discipline requiring robust validation.
• Quantitative analysis of toolmarks, aided by advanced imaging, is crucial for improving identification accuracy.
• Existing methods for knife mark analysis lack comprehensive validation, especially concerning real-world stabbing simulations.

Purpose of the Study:

• To statistically explore quantitative toolmark properties derived from micro-CT imaging of simulated knife stabbings.
• To assess the potential of micro-CT data for predicting knife characteristics, such as type (serrated vs. plain) and edge thickness.
• To evaluate the utility of scanning electron microscopy (SEM) for knife mark striation analysis and compare observer judgments from different imaging modalities.

Main Methods:

• Simulated stabbings were conducted using a mechanical rig on dry pig ribs and fleshed pig torsos.
• Knife marks were captured using micro-CT scanning, laser scanning, and scanning electron microscopy.
• Quantitative measurements of toolmark properties (width, angle, shape, striations) were statistically analyzed.

Main Results:

• Micro-CT imaging revealed statistically significant differences in cut mark width, wall angle, and shape between different knives.
• Knife type (serrated or plain) was predictable from cut mark width and wall angle, with knife edge thickness correlating to cut mark width.
• Observer judgments of cut mark shape were more consistent using micro-CT images compared to light microscopy; SEM was not found useful for striations.

Conclusions:

• Quantitative analysis of micro-CT scanned knife marks shows significant potential for identifying the responsible knife in forensic investigations.
• The study demonstrates the feasibility of predicting knife characteristics from quantitative measurements of simulated stab wounds.
• Combining micro-CT data with other imaging techniques can facilitate the creation of realistic virtual models for visualization and 3D printing.