Opinion ID: 1160857
Heading Depth: 2
Heading Rank: 7

Heading: Effects of Population Substructurethe Ceiling Principles

Text: The foregoing application of the product rule to calculate the frequency of a multi-locus profile will produce an accurate result only to the extent that each multiplied frequency is statistically independent from all the others. (See People v. Collins (1968) 68 Cal.2d 319, 328-329, 66 Cal.Rptr. 497, 438 P.2d 33.) Population genetics theory teaches that pairs of alleles at the same locus are statistically independent from each other if they are in Hardy-Weinberg equilibrium. Hardy-Weinberg equilibrium has been defined as the condition, for a particular genetic locus and a particular population, with the following properties: allele frequencies at the locus are constant in the population over time and there is no statistical correlation between the two alleles possessed by individuals in the population; such a condition is approached in large randomly mating populations in the absence of selection, migration, and mutation. (1992 NRC Rep., supra, p. 169 [Glossary], italics added; see id. at p. 78; 1996 NRC Rep., supra, pp. 90-92.) Alleles at different loci are said to be independent if they are in linkage equilibrium. Alleles are not in linkage equilibrium if a specific allele at one locus is nonrandomly associated with an allele at another locus. (1992 NRC Rep., supra, p. 170 [Glossary]; see id. at p. 78; 1996 NRC Rep., supra, p. 106.) Generally, the presence of both kinds of equilibrium in a given population depends on the extent to which mating within that population has been at random. If both kinds of equilibrium are not present, application of the product rule in theory may prejudice the suspect by understating the frequency of a profile within particular segments of the population. Major laboratories that do RFLP analysis, including the FBI and Cellmark [and the OCSD crime laboratory in this case], have developed their own separate population databases for each of several broad racial or ethnic categories such as Caucasian, Black, and Hispanic (see Barney, supra, 8 Cal.App.4th at p. 809, 10 Cal. Rptr.2d 731), the assumption being that mating among members of any one of those categories of the United States population is sufficiently random to justify using them in conjunction with the product rule to calculate the frequency of a DNA profile. (See 1996 NRC Rep., supra, p. 156.) [18]