Moisture-wicking properties of fabric and their effect on blood and the angle of impact

Abstract

The use of angle of impact calculations within bloodstain pattern analysis is limited to researched surface types which currently include smooth, non-porous materials and cotton. The purpose of this study was to determine if the existing equation for angle of impact could accurately be applied to moisture-wicking polyester. This study used posterboard as a control and tested three different polyester fabrics (100% polyester, 80% polycotton, and 20% polycotton). Bovine blood was dropped onto each of the four surfaces at 10° increments from 10° to 90°. The resulting stains were measured with digital calipers used in conjunction with drafting dividers. The measurements were analyzed using ANOVA and Tukey’s multiple comparisons test to determine and evaluate the significant differences between the surface types and the actual angles. The results showed that polyester significantly affected the ability to calculate angle of impact to within ±5°. The wicking property of polyester distorted the stains disproportionately so the angle of impact calculations were inaccurate at some angles. All three polyester samples had accurate calculations from 10° to 40°, but outside of that range, calculations were inconsistent and inaccurate. This information broadens the understanding of bloodstain analysis and can assist analysts in understanding the weight of their findings.