Blood pattern analysis—a review and new findings

Background Blood is one of the most common pieces of evidence encountered at the crime scene. Due to the viscous nature of blood, unique bloodstain patterns are formed which when studied can reveal what might have happened at the scene of the crime. Blood pattern analysis (BPA), i.e., the study of shape, size, and nature of bloodstain. The focus of this paper is to understand blood and BPA. An experimental finding to understand blood stain formation using Awlata dye was conducted within the university premises under laboratory conditions. Awlata (Alta), an Indian dye used for grooming of women, was used to create fake blood stains to understand the formation of bloodstains with respect to varying heights, and their relation with spines and satellite stains was determined. Results When the height of dropping fake blood increased, the distance of satellite stains emerging from the fake blood stains was also increasing. From the experimental finding, it was found that satellite stains were directly proportional to height of blood stain and spines were inversely proportional. Conclusion It can be concluded that blood is a vital source of information and when interpreted correctly it can be used as a source of information that can aid in investigations. Thus, a relation between formation of blood stains with relation to height was established. This finding using fake blood stains can help in carrying out future studies.

Ten years of molecular ballistics—a review and a field guide

Molecular ballistics combines molecular biological, forensic ballistic, and wound ballistic insights and approaches in the description, collection, objective investigation, and contextualization of the complex patterns of biological evidence that are generated by gunshots at biological targets. Setting out in 2010 with two seminal publications proving the principle that DNA from backspatter collected from inside surfaces of firearms can be retreived and successfully be analyzed, molecular ballistics covered a lot of ground until today. In this review, 10 years later, we begin with a comprehensive description and brief history of the field and lay out its intersections with other forensic disciplines like wound ballistics, forensic molecular biology, blood pattern analysis, and crime scene investigation. In an application guide section, we aim to raise consciousness to backspatter traces and the inside surfaces of firearms as sources of forensic evidence. Covering crime scene practical as well as forensic genetic aspects, we introduce operational requirements and lay out possible procedures, including forensic RNA analysis, when searching for, collecting, analyzing, and contextualizing such trace material. We discuss the intricacies and rationales of ballistic model building, employing different tissue, skin, and bone simulants and the advantages of the “triple-contrast” method in molecular ballistics and give advice on how to stage experimental shootings in molecular ballistic research. Finally, we take a look at future applications and prospects of molecular ballistics.

Beginning with Blood Patterns: Surface material and case information effects on trainee analysts’ judgments

There is growing concern about human bias and limitations in forensic science practice. The United States National Academy of Sciences has specifically highlighted that forensic sciences “rely on human interpretation of what could be tainted by error” (Edwards and Gotsonis, 2009, p9). An array of literature has shown that particular domains of forensic science, such as fingerprint and DNA matching, are vulnerable to bias and error. Less attention has been paid to the process of blood pattern analysis. In the current study, a sample of 32 trainee blood pattern analysts from the United Kingdom were asked to report the number and type of stains present on six different surfaces. The surfaces were systematically varied in terms of colour and porosity. Further, participants were provided with ‘case information’ to investigate if details about the source of the stains would bias a re-appraisal of the stains. We found that the trainees found the dark, non-porous surfaces particularly challenging when identifying the number of stains present on a surface. The accuracy at detecting the specific types of stain varied more as a function of the individual trainee than the surface material. Case information had no effect on participants reappraising the stains. The results highlight particular materials that may require targeted tutoring for trainee blood pattern analysts.