A Large-Scale Study of Bloodstain Ellipse Marking
Eugene Liscio, P. Eng., Craig C. Moore
Abstract
The individual bloodstain remains the most fundamental element of an overall bloodstain pattern and as such, requires the attention of further research. In this study, a total of 454 participants were able to complete a bloodstain ellipse marking study of 18 images of bloodstains with varying impact and directional angles. The results agree with past studies that show a trend of increasing errors when marking bloodstains with impact angles closer to 90° [1]. The average error for the impact angle (a) at 90° was found to be close to 8° (n=454) with a standard deviation of approximately 5°. The directional component or gamma angle (?) was found to have large errors between known impact angles of 70°-90° (n=205). In some cases, participants estimated the gamma angle to be in the opposite direction from the known direction. The data obtained in this study may be used in the future to determine the uncertainty of errors when utilizing methods such as 3D Area of Origin analysis and Area of Convergence for impact spatter, and Path Volume Envelope for cast-off stains.
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