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A preliminary investigation into the influence of case information and surface material effects on the judgments of forensic science undergraduate students within the discipline of bloodstain pattern analysis

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.