markers tested so far cannot be taken to mean that such does not exist for other markers. Preservation of population DNA samples in the form of immortalized cell lines will ensure that DNA is available for determining population frequencies of any DNA pattern as new and better techniques become available, without the necessity of collecting fresh samples. It will also provide samples for standardization of methods across laboratories.

Because of the similarity in DNA patterns between relatives, databanks of DNA of convicted criminals have the ability to point not just to individuals but to entire families—including relatives who have committed no crime. Clearly, this raises serious issues of privacy and fairness. It is inappropriate, for reasons of privacy, to search databanks of DNA from convicted criminals in such a fashion. Such uses should be prevented both by limitations of the software for searching and by statutory guarantees of privacy.

The genetic correlation among relatives means that the probability that a forensic sample will match a relative of the person who left it is considerably greater than the probability that it will match a random person.

Especially for a technology with high discriminatory power, such as DNA typing, laboratory error rates must be continually estimated in blind proficiency testing and must be disclosed to juries.

Recommendations

  • As a basis for the interpretation of the statistical significance of DNA typing results, the committee recommends that blood samples be obtained from 100 randomly selected persons in each of 15-20 relatively homogeneous populations; that the DNA in lymphocytes from these blood samples be used to determine the frequencies of alleles currently tested in forensic applications; and that the lymphocytes be ''immortalized" and preserved as a reference standard for determination of allele frequencies in tests applied in different laboratories or developed in the future. The collection of samples and their study should be overseen by a National Committee on Forensic DNA Typing.

  • The ceiling principle should be used in applying the multiplication rule for estimating the frequency of particular DNA profiles. For each allele in a person's DNA pattern, the highest allele frequency found in any of the 15-20 populations or 5% (whichever is larger) should be used.

  • In the interval (which should be short) while the reference blood samples are being collected, the significance of the findings of multilocus DNA typing should be presented in two ways: (1) If no match is found with any sample in a total databank of N persons (as will usually be the case), that should be stated, thus indicating the rarity of a random match. (2) In applying the multiplication rule, the 95% upper confidence limit of the frequency of each allele should be calculated for separate U.S. "racial"



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