Bloodstain pattern analysis with infrared photography as a tool to visualize impact and satellite spatter on denim.

Abstract

Correctly classifying bloodstain patterns is a crucial element of providing conclusions in the field of Bloodstain Pattern Analysis, because the type of bloodstain pattern speaks to how the bloodstains were created. Very few studies have compared impact spatter specifically to satellite spatter. The research needs outlined by SWGSTAIN include a better understanding of discriminating between bloodstain patterns containing small stains (present in both impact and satellite spatter), how blood interacts with different types of fabric, and developing new methods of visualizing and enhancing bloodstains (2011). Further, the Organization of Scientific Area Committee (OSAC) on BPA, which absorbed SWGSTAIN, outlines needs to reduce the subjectivity in BPA classification and understanding the interaction between blood and fabrics (OSAC, 2019). The only study to the author's knowledge that specifically compares satellite spatter to impact spatter is Short's 2016 study, which compared the two patterns on several different fabrics. However, Short was not able to visualize spatter on denim, due to dark color of the denim and lack of contrast between the blood and denim surface. The current study used infrared photography to view simulated satellite spatter and impact spatter on 100% cotton denim and poster board. Both quantitative and qualitative data were collected. Two-way ANOVA, Cochran-Mantel-Haensel, and chi-square tests were performed on the data. Several comparisons found either a significant interaction, difference, or association between independent and dependent variables, depending on the test performed and the type of data analyzed. Overall, by utilizing the methods in this study, it is possible to differentiate between simulated impact and satellite spatter on denim fabric.