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Determining the area of convergence in Bloodstain Pattern Analysis: a probabilistic approach

A complete procedure for identifying the area of convergence of blood drops originated from a single static source is presented. Both for bloodstains lying on an horizontal and on a vertical plane a complete study is developed, based on error analysis and on an opportunely defined joint probability density for the orientation of the horizontal projections of the trajectories of the drops. The method generates a probabilistic map for the area of convergence, directly linking the angles of impact, and their uncertainties, to the projection on the ground of the point of origin. One of the objectives consists in providing a statistical definition of area of convergence, extending to this topic the mathematical accuracy of the calculation of the angle of impact in bloodstain pattern analysis (BPA).