the possibility of the death penalty, the reliability of the evidence offered against the defendant was critically important.79
The same concerns cited by the judge in Maryland v. Rose can be raised with respect to other forensic techniques that lack scientific validation and careful reliability testing.
Review of reported judicial opinions reveals that, at least in criminal cases, forensic science evidence is not routinely scrutinized pursuant to the standard of reliability enunciated in Daubert. The Supreme Court in Daubert indicated that the subject of an expert’s testimony should be “scientific knowledge”—which implies that such knowledge is based on scientific methods—to ensure that “evidentiary reliability will be based upon scientific validity.” The standard is admittedly “flexible,” but that does not render it meaningless. Any reasonable reading of Daubert strongly suggests that, when faced with forensic evidence, “trial judge[s] must ensure that any and all scientific testimony or evidence admitted is not only relevant, but reliable.” As the reported cases suggest, however, Daubert has done little to improve the use of forensic science evidence in criminal cases.
For years in the forensic science community, the dominant argument against regulating experts was that every time a forensic scientist steps into a courtroom, his work is vigorously peer reviewed and scrutinized by opposing counsel. A forensic scientist might occasionally make an error in the crime laboratory, but the crucible of courtroom cross-examination
Professor Jennifer Mnookin has also highlighted an important concern over “the rhetorical dimensions of the testimony … provide[d] in court” by members of the fingerprint community:
At present, fingerprint examiners typically testify in the language of absolute certainty. Both the conceptual foundations and the professional norms of latent fingerprinting prohibit experts from testifying to identification unless they believe themselves certain that they have made a correct match. Experts therefore make only what they term “positive” or “absolute” identifications—essentially making the claim that they have matched the latent print to the one and only person in the entire world whose fingertip could have produced it. In fact, if a fingerprint examiner testifies on her own initiative that a match is merely “likely” or “possible” or “credible,” rather than certain, she could possibly be subject to disciplinary sanction! Given the general lack of validity testing for fingerprinting; the relative dearth of difficult proficiency tests; the lack of a statistically valid model of fingerprinting; and the lack of validated standards for declaring a match, such claims of absolute, certain confidence in identification are unjustified, the product of hubris more than established knowledge. Therefore, in order to pass scrutiny under Daubert, fingerprint identification experts should exhibit a greater degree of epistemological humility. Claims of “absolute” and “positive” identification should be replaced by more modest claims about the meaning and significance of a “match.”
J.L. Mnookin. 2008. The validity of latent fingerprint identification: Confessions of a fingerprinting moderate. Law, Probability and Risk 7(2):127; see also Koehler, supra note 71.