The Reliability of Pattern Classification in Bloodstain Pattern Analysis—PART 2: Bloodstain Patterns on Fabric Surfaces

• Michael C. Taylor ^[2] ; Terry L. Laber ^[3] ; Paul E. Kish ^[4] ; Glynn Owens ^[1] ; Nikola K. P. Osborne ^[2]
  1. [1] University of Auckland

     University of Auckland

     Nueva Zelanda

     
  2. [2] Institute of Environmental Science and Research Limited (ESR) Christchurch New Zealand
  3. [3] Minnesota Bureau of Criminal Apprehension (BCA) St Paul MN
  4. [4] Forensic Consultant & Associates Corning NY

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• Localización: Journal of forensic sciences, ISSN-e 1556-4029, ISSN 0022-1198, Vol. 61, Nº. 6, 2016, págs. 1461-1466
• Idioma: inglés
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• Resumen

  • This study was designed to produce the first baseline measure of the reliability of bloodstain pattern classifications on fabric surfaces. Experienced bloodstain pattern analysts classified bloodstain patterns on pairs of trousers that represented three fabric substrates. Patterns also varied in type (impact, cast-off, expiration, satellite stains from dripped blood, and transfer) and extent. In addition, case summaries that accompanied each pattern contained contextual cues that either supported the correct answer (i.e., positive bias), were misleading toward an incorrect answer (i.e., negative bias), or contained no directional information (i.e., neutral). Overall, 23% percent of the resulting classifications were erroneous. The majority (51%) of errors resulted from analysts misclassifying satellite stains from dripped blood. Relative to the neutral information, the positive-bias information increased correct classifications and decreased erroneous classifications, and the negative-bias information decreased correct classifications and increased erroneous classifications. The implications of these findings for BPA are discussed.