Chapter 4: Bloodstain Pattern Analysis Check Access

Bloodstain pattern analysis (BPA) is a discipline within forensic science that deals with the examination and identification of bloodstains and the interpretation and evaluation of those bloodstains to attempt to establish the activities that may have caused them. Human observation forms a significant component of BPA and, as a consequence, it is widely considered to be subjective. However, the discipline is underpinned by sound scientific principles and a body of research that dates back to at least the late 19th century. Through an understanding of pattern recognition, how the physiological characteristics of blood influence stain formation, how blood interacts with surfaces and the factors that impact on the mechanisms by which blood can be distributed in various scenarios, allow analysts an understanding of how blood might be expected to transfer in various situations. As with many forensic disciplines it is rare to be able to offer a definitive BPA opinion; however, by understanding the strengths and limitations (and communicating these properly) a robust conclusion is achievable. This chapter introduces the history and key developments in the discipline of BPA including the frameworks available to identify and classify bloodstain patterns, and mathematical principles that underpin blood dynamics. An overview of the main spatter patterns as well as altered blood and transfer patterns, provides a foundation in BPA classification, and the chapter concludes with a brief look at the scientific approach to BPA, including an appreciation of the approaches to the evaluation of bloodstaining and management of bias.