The research represented an effort to reduce possible sources of influence or bias that could produce errors in the hair testing, which partly involves the subjective opinion of the examiner. The subjects were 14 students in advanced crime laboratory college courses. They received 60 hours of lectures and 60 hours of laboratory experience in human hair identification techniques. Each examiner examined and compared human hair evidence in four criminal investigations. Half of the 56 fictitious cases were prepared in the usual manner with questioned hair material recovered from the crime scene, known hair samples from one suspect, and a brief synopsis of the facts surrounding the case. None of the known hair samples came from the same person as the questioned hair, although they were similar in pigmentation, color, scale patterns, length, and width. The other 28 cases also had no true matches between suspects and crime-scene hair. However, 5 samples of each suspect's hair were included for each of the 28 cases. These 28 cases were submitted to the hair examiners following the guidelines of lineup procedures. The regular procedure produced an error rate of 30.4 percent, while the rate for the alternative procedure was 3.8 percent. Findings raise concern regarding the amount of unintentional bias among human hair identifiers. The current method of submitting hair evidence for analysis may encourage this bias. Using lineup procedures can reduce the potential impact of preconceived notions. 31 references.