Gary Sims, a criminalist with the California Department of Justice, served as a prosecution DNA witness in the criminal trial and later testified in the civil trial. In the criminal case, he presented RFLP and PCR analyses of blood evidence from the Bronco, the Rockingham glove, Simpson's socks, and the Bundy crime scene, including a reported statistic of one in 21 billion for Nicole Brown Simpson's blood on sock A. Examined by prosecutor Rockne Harmon and cross-examined at length by Barry Scheck, Sims faced defense challenges concerning contamination and evidence handling, including changes in measured DNA content in Bronco samples and degradation issues involving rear-gate stains. Before his listed witness examinations began, he addressed the timing of ongoing DOJ testing during a hearing in which Scheck alleged a "forensic ambush" and sought preclusion of results; in the civil trial, defense attorney Blasier challenged Sims about faint PCR results, chain-of-custody protocols, and statistical calculations.