Dr. William Shields was the defense population geneticist called on June 22, 1995, after prosecution expert Dr. Bruce Weir testified about frequency calculations for mixed blood stains. Shields testified during a foundational hearing under Evidence Code section 402, held outside the jury's presence, and challenged Weir's mixture-statistics methodology as dependent on assumptions and potentially misleading. William Thompson conducted the direct examination, redirect, and further redirect, while George Clarke conducted a two-part cross-examination and recross; Shields also participated in proceedings concerning DNA statistical evidence.