Procedural Bias in Forensic Science Examinations of Human Hair

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Several forms of expert forensic science evaluations exist that rely at least in part on the subjective opinion of the examiner. Human hair identification is one such examination. This paper considers possible sources of influence or bias that may be responsible for examiner errors. Data are reported of an experiment that compares the conventional examination procedure (known versus questioned samples) against an alternative procedure (a lineup of samples) designed to limit the influence of factors that contribute to error. The altenative procedure produced fewer incorrect conclusions (3.8%) than the conventional procedure (30.4%).