whether the types match and thus whether the samples could have come from the same source.

  1. If the types match, statistical analysis of the population frequencies of the types to determine the probability that a match would have been observed by chance in a comparison of samples from different persons.

Before any particular DNA typing method is used for forensic purposes, precise and scientifically reliable procedures for performing all three steps must be established. It is meaningless to speak of the reliability of DNA typing in general—i.e., without specifying a particular method.

Despite the challenges of forensic DNA typing, it is possible to develop reliable forensic DNA typing systems, provided that adequate scientific care is taken to define and characterize the methods.

Recommendations

  • Any new DNA typing method (or a substantial variation of an existing method) must be rigorously characterized in both research and forensic settings, to determine the circumstances under which it will yield reliable results.

  • DNA analysis in forensic science should be governed by the highest standards of scientific rigor, including the following requirements:

    • Each DNA typing procedure must be completely described in a detailed, written laboratory protocol.

    • Each DNA typing procedure requires objective and quantitative rules for identifying the pattern of a sample.

    • Each DNA typing procedure requires a precise and objective matching rule for declaring whether two samples match.

    • Potential artifacts should be identified by empirical testing, and scientific controls should be designed to serve as internal checks to test for the occurrence of artifacts.

    • The limits of each DNA typing procedure should be understood, especially when the DNA sample is small, is a mixture of DNA from multiple sources, or is contaminated with interfering substances.

    • Empirical characterization of a DNA typing procedure must be published in appropriate scientific journals.

    • Before a new DNA typing procedure can be used, it must have not only a solid scientific foundation, but also a solid base of experience.

  • The committee strongly recommends the establishment of a National Committee on Forensic DNA Typing (NCFDT) under the auspices of an



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