Comment on 'Scientific validation of fingerprint evidence under Daubert'

Abstract

I have been asked to comment on the strangest article. Lyn and Ralph Haber describe a forensic assay that apparently has been offered in court at least 100 000 times over the last century in the United States alone; that offers conclusions of ‘individualization’ linking trace evidence to a single individual, to the exclusion of all other potential sources in the universe; and whose rate of error, proponents have claimed in sworn testimony, is ‘zero’. Yet, the article reports, there has been no empirical validation of this assay or even of its component steps. Worse still, the necessary preliminary steps for carrying out validation, such as producing an agreed upon published protocol, developing a standardized form for reporting conclusions and developing a metric of trace similarity, have not yet been done—100 years after the assay was first made the subject of sworn expert testimony in court. In place of empirical validation data, the proponents of this technique and the attorneys who employ it muster obviously bankrupt and deceptive arguments, such as the assay is valid because it has been accepted by courts and its own practitioners for 100 years; the assay is valid because each case in which it was used constituted a de facto test of its validity; the assay is valid because multiple analysts ‘usually’ (but how often is not specified) reach consistent conclusions; and the assay is valid when used by a competent analyst (an argument that is sustained by deeming all analysts implicated in exposed errors as ‘incompetent’ in post hoc fashion). I must admit that I was surprised and perplexed by the Habers’ claims and even a bit incredulous as to whether the situation they described was real or some sort of figment of their joint imagination. How could such a state of affairs exists? All confusion dissipated, however, when I realized that the technique they were describing was ‘Analysis, Comparison, Evaluation–Verification’ (ACE-V), the current term favoured by North American latent print examiners (LPEs) for the ‘methodology’ of latent print individualization, a forensic technique that has demonstrated an astonishing ability to defy one’s expectations of both science and law. Readers of an older generation who received some training in latent print identification may find themselves surprised by the reference to ‘ACE-V’ to describe a process which may have been taught to them simply as ‘latent print comparison’. One’s training in latent prints need not be that old for one to have never heard the term ‘ACE-V’. As recently as 2001, Olsen and Lee (2001) saw no need to name ‘the dominant method’ of latent print analysis other than to call it ‘the conventional method’. Readers with backgrounds in science, meanwhile, may find themselves perplexed by references to ACE-V as a ‘methodology’ when ACE-V, which essentially lays out loosely defined steps of analysing prints, comparing their features, evaluating whether there is sufficient consistency to warrant a conclusion of ‘individualization’ and then repeating the process (‘verification’), would seem to