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Reliability Assessment of Current Methods in Bloodstain Pattern Analysis

Reliability Assessment of Current Methods in Bloodstain Pattern AnalysisTerry Laber, Paul Kish, Michael Taylor, Glynn Owens, Nikola Osborne, James Curran. June 2014. The author(s) shown used Federal funds provided by the U.S. Department of Justice in preparing this final report. Final Report for the National Institute of Justice
Award # 2010-DN-BX-K213.

“To date there have been relatively few error rate or validation studies in BPA and none has investigated the role that contextual information might have on analysts’ conclusions. This study was designed to produce the first baseline measure of reliability for the major BPA method of pattern recognition. The approach used was designed to help define the upper limit of pattern classification reliability by focusing attention on method reliability rather than analyst competency. A panel of experienced bloodstain pattern analysts examined over 730 patterns in two phases of the study, one focussing on three rigid non-absorbent surfaces (painted wood, wallpaper and chipboard) representing commonly encountered crime scene surfaces and the other on three fabric surfaces (cotton sweatpants, polyester trousers and demin jeans) representing clothing. Six different pattern types, blunt force impact spatter, firearms (back and forward) spatter, cast-off, satellite stains from a drip pattern, transfer and expirated, were used over the two studies. The extent of available pattern, the nature of the substrate and the type of contextual information (positive, negative and neutral bias) were varied in a balanced experiment designed to determine the effect of these variables on pattern classification accuracy. As a small adjunct to the main focus on pattern recognition, a set of superimposed bloodstains prepared on non-absorbent rigid surfaces was also included for sequence of events determinations.”

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