Estimating the Area of Origin (AO) of an impact pattern requires the analysis of multiple bloodstains within a single frame of reference. Traditional methods rely on manual measurements of stain coordinates, requiring significant time and effort. HemoVision uses an automated approach relying on fiducial markers, eliminating the need for tedious manual work.
To prepare an impact pattern for analysis with HemoVision, several fiducial markers are placed around the impact pattern. Each of these markers contain a black-and-white checkerboard pattern and a binary identification (except for the larger overview marker). Once placed, the pattern can be photographed. One overview image to encompass the complete pattern, and an arbitrary number of detailed close-up images for stain analysis.
The photographs are then loaded into HemoVision, after which all markers are detected using traditional computer-vision algorithms. Based on the detected markers, all photographs are mapped into a common frame of reference. Stain parameters can then be estimated using the ellipse model or HemoVision's statistical shape model (more info). Finally, the convergence of the estimated stain trajectories can be estimated using any preferred method.
By using these markers, HemoVision eliminates the need for measuring stain coordinates. Moreover, photographs can be taken freehand, because any parallax errors are corrected programmatically afterwards. This significantly reduces the time needed to estimate the AO of an impact pattern.
For more information about this study, please refer to the full article here.
Based on: Joris, Philip, et al. "HemoVision: An automated and virtual approach to bloodstain pattern analysis." Forensic Science International 251 (2015): 116-123.
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