This Letter to the Editor proposes a two-step structure for bloodstain pattern analysis (BPA) that distinguishes between observation of the features of the bloodstain and a reconstruction of events that explain the characteristics of the bloodstain pattern.
Although most bloodstain-pattern analysts would contend that they make observations about the size, shape, and distribution of bloodstains as the first step in their analysis, the current method for pattern classification does not provide analysts with a platform for clearly reporting “observation-only” findings. The author argues for a well-defined process that distinctly separates the currently overlapping components into a two-step method for BPA. The proposed “Step One” is limited to the characterization of the pattern, i.e., observing and measuring the bloodstain’s features. This step should be completed and fully documented before proceeding to “Step Two.” Step Two consists of analysts forming opinions about the events that produced the features of the bloodstain. This may also involve incorporating relevant contextual information, such as the nature of the victim’s injuries and other information related to events at the scene of the bloodstain. It is argued that such a clearly defined two-step process for BPA would bring more objectivity and transparency to the conclusions of the bloodstain analyst. 6 references
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