or otherwise compromised sample cannot reliably identify or eliminate an individual as the perpetrator of a crime. These are important matters having to do with the proper “processing” of forensic evidence. The law’s greatest dilemma in its heavy reliance on forensic evidence, however, concerns the question of whether—and to what extent—there is science in any given “forensic science” discipline.3

The degree of science in a forensic science method may have an important bearing on the reliability of forensic evidence in criminal cases. There are two very important questions that should underlie the law’s admission of and reliance upon forensic evidence in criminal trials: (1) the extent to which a particular forensic discipline is founded on a reliable scientific methodology that gives it the capacity to accurately analyze evidence and report findings and (2) the extent to which practitioners in a particular forensic discipline rely on human interpretation that could be tainted by error, the threat of bias, or the absence of sound operational procedures and robust performance standards. These questions are significant:4 The goal of law enforcement actions is to identify those who have committed crimes and to prevent the criminal justice system from erroneously convicting the innocent. So it matters a great deal whether an expert is qualified to testify about forensic evidence and whether the evidence is sufficiently reliable to merit a fact finder’s reliance on the truth that it purports to support.

As discussed in Chapters 4 and 5, no forensic method other than nuclear DNA analysis has been rigorously shown to have the capacity to consistently and with a high degree of certainty support conclusions about “individualization” (more commonly known as “matching” of an unknown item of evidence to a specific known source). In terms of scientific basis, the analytically based disciplines generally hold a notable edge over disciplines based on expert interpretation. But there also are important variations among the disciplines relying on expert interpretation. For example, there are more established protocols and available research for the analysis of fingerprints than for bite marks. In addition, there also are significant variations within each discipline. Thus, not all fingerprint evidence is equally good, because the true value of the evidence is determined by the quality of the latent fingerprint image. In short, the interpretation of forensic evidence is not infallible. Quite the contrary. This reality is not always fully appre-

3

Principles of science are discussed in Chapter 4.

4

Descriptions and assessments of different forensic science disciplines are set forth in Chapters 5 and 6.



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