An Investigation into Bloodstain Pattern Analysis: The Reliability of Swipe/Wipe and Directionality Determination Approaches

Swipe/wipe patterns are some of the most common bloodstain patterns encountered at bloodied crime scenes. These patterns can be pivotal to describing the events that occurred at the time of a crime, as well as determining the accuracy of a witness statement. Recently, a study from the University of Auckland was published, stating that the overall error rate of swipe/wipe pattern classifications was 32%. This high error rate is a problem because an incorrect pattern classification could have a large impact on the outcome of legal proceedings. The aim of this project is to test current bloodstain pattern analysis (BPA) protocol reliability, to see how much, if at all, the material effects classification accuracy, and to expand on the study from the University of Auckland. Only a small amount of published data is available on this subject, and considering the alarming error rate, more data is needed to ensure bloodstain pattern analysis methods are dependable. To examine this, swipe/wipe patterns were created using 4 different materials. The patterns were then photographed and sent to BPA experts all over Canada, and internationally. All patterns were created by simply deploying the chosen pattern type in a left or right fashion with the chosen material. It should also be noted that all patterns were created by the same researcher. This study is still in progress, to date the error rate for pattern determination is 17.5 %, and the error rate for direction determination is 6.6%. If the data continues to display this trend, a new protocol should be considered to improve the pattern classification error rate. Also, the data will be able to identify any trends associated with a specific material being more likely to cause an incorrect classification. This project could improve the future of BPA protocol