The Reliability of Pattern Classification in Bloodstain Pattern Analysis, Part 1: Bloodstain Patterns on Rigid Non-absorbent Surfaces.
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.
Institute of Environmental Science and Research Limited (ESR), PO Box 29-181, Christchurch, New Zealand.
Michael C
MC
Taylor
Minnesota Bureau of Criminal Apprehension (BCA), 1430 Maryland Ave East, St Paul, MN, 55106.
Terry L
TL
Laber
Forensic Consultant & Associates, PO Box 814, Corning, NY, 14830.
Paul E
PE
Kish
School of Psychology, University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand.
Glynn
G
Owens
Institute of Environmental Science and Research Limited (ESR), PO Box 29-181, Christchurch, New Zealand.
Nikola K P
NK
Osborne
D001801:Blood Stains; D005554:Forensic Medicine; D006801:Humans; D007600:Judgment; D015203:Reproducibility of Results
bloodstain pattern analysis; cognitive science; contextual bias; error rate; forensic science; reliability