334
Stevens, J., dissenting
specific evidence. But such questions are properly addressed in adversary proceedings; they fall far short of justifying a blanket exclusion of this type of expert testimony.
There is no legal requirement that expert testimony must satisfy a particular degree of reliability to be admissible. Expert testimony about a defendant's "future dangerousness" to determine his eligibility for the death penalty, even if wrong "most of the time," is routinely admitted. Barefoot v. Estelle, 463 U. S. 880, 898-901 (1983). Studies indicate that handwriting analysis, and even fingerprint identifications, may be less trustworthy than polygraph evidence in certain cases.24 And, of course, even highly dubious eyewit-24 One study compared the accuracy of fingerprinting, handwriting analysis, polygraph tests, and eyewitness identification. The study consisted of 80 volunteers divided into 20 groups of 4. Fingerprints and handwriting samples were taken from all of the participants.
In each group of four, one person was randomly assigned the role of "perpetrator." The perpetrator was instructed to take an envelope to a building doorkeeper (who knew that he would later need to identify the perpetrator), sign a receipt, and pick up a package. After the "crime," all participants were given a polygraph examination.
The fingerprinting expert (comparing the original fingerprints with those on the envelope), the handwriting expert (comparing the original samples with the signed receipt), and the polygrapher (analyzing the tests) sought to identify the perpetrator of each group. In addition, two days after the "crime," the doorkeeper was asked to pick the picture of the perpetrator out of a set of four pictures.
The results of the study demonstrate that polygraph evidence compares favorably with other types of evidence. Excluding "inconclusive" results from each test, the fingerprinting expert resolved 100% of the cases correctly, the polygrapher resolved 95% of the cases correctly, the handwriting expert resolved 94% of the cases correctly, and the eyewitness resolved only 64% of the cases correctly. Interestingly, when "inconclusive" results were included, the polygraph test was more accurate than any of the other methods: The polygrapher resolved 90% of the cases correctly, compared with 85% for the handwriting expert, 35% for the eyewitness, and 20% for the fingerprinting expert. Widacki & Horvath, An Experimental Investigation of the Relative Validity and Utility of the Polygraph Technique and Three Other Common Methods of Criminal Identification, 23 J. Forensic Sciences 596, 596-600 (1978); see also Honts & Perry 365.
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