What is the test for determining statistical significance between a DNA sample from a crime scene and that of a suspect?

'Because there is no practical way to sequence all three billion base pairs in a person's DNA, forensic scientists seek to identify individuals through variations in their base-pair sequences at polymorphic DNA locations (loci) [, where the sequence of base pairs varies from person to person]. Each variation in a [base-pair] sequence . . . is called an "allele." . . . In the absence of a nonmatch that conclusively eliminates the suspect as the source of the crime scene sample, each match between alleles from the suspect and from the crime scene may be accorded statistical significance.' [Citations.]" (People v. Cua (2011) 191 Cal.App.4th 582, 592-593.) To do so, "the DNA profile of the matched samples is compared to the DNA profiles of other available DNA samples in a relevant population database or databases in order to determine the statistical probability of finding the matched DNA profile in a person selected at random from the population or populations to which the perpetrator of the crime might have belonged." (People v. Soto (1999) 21 Cal.4th 512, 518.)

1. Background