A preliminary study: Cast-off bloodstain pattern analysis with HemoVision

Bloodstain pattern analysis (BPA) is performed as part of forensic crime scene investigations to classify and interpret bloodstains in the context of the crime scene. HemoVision is a BPA computer software package that automates the documentation, analysis, and visualization of bloodstain patterns. This study aimed to assess the accuracy of HemoVision's beta cast-off bloodstain pattern analysis feature. A wooden rig with a circular swing path was used to create 36 controlled cast-off bloodstain patterns with downward vertical, upward vertical, and downward diagonal swings. Of these tests, six were conducted as blind trials where the analyst was absent for the bloodstain pattern creation. HemoVision estimated the x, y, and z axis positions of the center of swing and the radius of swing, which were compared to the known values. The average absolute errors of the estimated three-dimensional center of swing were determined to be 16.2 ± 6 cm, 27.3 ± 9 cm, 16.6 ± 8 cm, and 12.2 ± 5 cm for the downward, upward, diagonal, and blind swing trials, respectively. It was determined that the x position (horizontal) was the most accurate and the y position (vertical) the least accurate. Furthermore, the cast-off swing path was estimated in HemoVision as a curved tubular shape with a diameter of 3σ, referred to as the tubular swing path envelope (TSPE). In all cases, the known swing path was partially or fully contained within the TSPE. Thus, HemoVision BPA can accurately estimate an area in which the bloody weapon was swung through.