NCJ Number
172959
Date Published
1998
Length
10 pages
Annotation
Two separate questions were investigated with grant funds from the National Institute of Justice that concerned the interpretation of stains containing DNA from more than one contributor and the characterization of DNA structure in human populations.
Abstract
A theory was established that considered all sets of individuals whose joint DNA profiles were the same as that from the stain. As with all interpretations of DNA evidence, the strength of evidence was expressed as the ratio of the probability of evidence if named persons were among the contributors to the probability of evidence if these persons were not contributors. The theory was then extended to allow contributors to be from different populations. Research showed the evidentiary strength of DNA evidence depended on the relationship between the person suspected of having contributed to a DNA profile and an unknown person, if different from the suspect, who was the actual contributor. This relationship may have simply reflected joint membership of the same population and may have been caused by the evolutionary history of that population. Estimates of population structure parameters gave results consistent with previous understanding of the evolution of modern humans and supported the use of forensic data bases collected as convenience samples. Effects of population structure were greatest for people within the same subpopulation of the same population, but it was determined these effects should not be ignored even for people from different racial groups. 11 references, 1 table, and 1 figure