Fingerprint Error Rates and Proficiency Tests: What They are and Why They Matter
Hastings Law Journal, Vol. 59, No. 5,p. 1077, May 2008
22 Pages Posted: 11 Oct 2009 Last revised: 18 Jan 2018
Date Written: 2008
When a fingerprint examiner declares a match between a print from a known source and a latent print recovered from a crime scene, his word may seal a defendant's fate like no other form of evidence save, perhaps, DNA. At trial the fingerprint examiner will offer little in the way of data, statistical tests, or uncertainty. Instead, he will say that latent print could only have been made by the source of the known print, that he is 100% certain, and that the method he used to make this and other identifications has an error rate of zero. In recent years, the broader scientific community has objected to this form of testimony. Critics charge that fingerprint analysis lacks an empirical foundation and that examiners make exaggerated claims that are likely to mislead jurors. In this Article, I use a question and answer style to address key issues related to fingerprint error rates and the proficiency tests that are sometimes used to estimate those rates. My focus throughout is on how to assess the various error rates, why they matter, and how we might go about collecting the requisite data. In Part I, I identify the different types of errors and error rates and explain why knowledge of error rates is important. In Part II, I discuss the connection between proficiency tests and estimated error rates. In Part III, I identify the features proficiency tests must include to ensure that the resultant data can help estimate casework error rates.
Keywords: Fingerprints, error rates, evidence
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