The Reliability of Pattern Classification in Bloodstain Pattern Analysis,Part 1: Bloodstain Patterns on Rigid Non‐absorbent Surfaces |
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| Authors: | Michael C Taylor PhD Terry L Laber BS Paul E Kish MSc Glynn Owens PhD Nikola K P Osborne PhD |
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| Affiliation: | 1. Institute of Environmental Science and Research Limited (ESR), Christchurch, New Zealand;2. Minnesota Bureau of Criminal Apprehension (BCA), St Paul, MN;3. Forensic Consultant & Associates, Corning, NY;4. School of Psychology, University of Auckland, Auckland, New Zealand |
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| Abstract: | This study was designed to produce the first baseline measure of reliability in bloodstain pattern classification. A panel of experienced bloodstain pattern analysts examined over 400 spatter patterns on three rigid non‐absorbent surfaces. The patterns varied in spatter type and extent. A case summary accompanied each pattern that either contained neutral information, information to suggest the correct pattern (i.e., was positively biasing), or information to suggest an incorrect pattern (i.e., was negatively biasing). Across the variables under examination, 13% of classifications were erroneous. Generally speaking, where the pattern was more difficult to recognize (e.g., limited staining extent or a patterned substrate), analysts became more conservative in their judgment, opting to be inconclusive. Incorrect classifications increased as a function of the negatively biasing contextual information. The implications of the findings for practice are discussed. |
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| Keywords: | forensic science bloodstain pattern analysis error rate reliability contextual bias cognitive science |
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