Survey of bloodstain pattern analysts regarding pattern classifications on assorted fabrics

Abstract

Because bloodstain pattern analysis (BPA) on absorbent surfaces, such as fabrics, is far more complex than its application on hard, nonporous surfaces, pattern type may be interpreted differently between fabric substrates and by analysts with more or less experience. Four bloodstain pattern types (impact spatter, transfer, drip stains, and cast-off) were created on seven fabrics (cotton, satin polyester, rayon, blended polyester/spandex, blended nylon/spandex, blended modal/polyester/spandex, and terry cloth), foamboard, or butcher paper and then photographed. A survey questionnaire that asked respondents to classify 16 patterns as to general pattern type, specific pattern type, and directionality was developed and disseminated among bloodstain pattern analysts. Respondents (n = 32, divided into five experience levels) classified the bloodstains differently based upon amounts of training and experience, the pattern type, and the substrate type. The ability to accurately classify the specific pattern type overall (p-value < 0.0002) as wells as on fabric (p-value < 0.001) was dependent upon respondent experience level. The more experienced respondents were less likely to specifically classify patterns than the less experienced respondents (p-value < 0.001). Furthermore, the ability to accurately classify the specific pattern type was dependent upon whether the pattern had been created on fabric or some other substrate (p-value < 0.0000000001). However, if the proper morphology was present in the stain, it was found that BPA on certain fabrics was possible. This finding supports the need for further research and the development of guidelines and standards for bloodstain pattern analysis on fabric materials.