Dr. John Gerdes concluded his testimony amid continued dispute over the defense's DNA contamination theory. On cross-examination he acknowledged numerous reported matches and said he had no direct evidence that Simpson's reference sample contaminated the Bronco stains, while continuing to stress sample conditions, mixtures, and contamination controls. Scheck's redirect used LAPD proficiency-test failures and the item 117 quantity comparison to support Gerdes's opinions; on recross, Gerdes acknowledged that he had not physically tested the proposed contamination mechanism and lacked several measurements relevant to comparing items 52 and 117. The defense then called UC Berkeley statistician Professor Terence Speed, who argued that DNA match probabilities should be accompanied by laboratory error rates and that valid error rates require external blind proficiency testing.

• Gerdes acknowledged reported multi-probe RFLP matches at the rear gate, on the sock, and on Bundy item 52, while maintaining that sample conditions, mixtures, contamination controls, and the evidentiary source of item 52 mattered
• Defense introduces slides documenting LAPD DNA lab proficiency test failures—contamination events undetected by negative controls—to rehabilitate contamination theory
• On recross, Gerdes acknowledged that he had not physically tested the proposed cross-contamination mechanism and lacked several measurements relevant to comparing items 52 and 117, while explaining that he relied on LAPD data and the samples' relative collection age
• Scheck highlighted item 117 as an anomaly: the rear gate sample contained 150 nanograms of DNA despite outdoor collection weeks later, five times the amount in any Bundy blood drop
• UC Berkeley statistician Professor Speed argues that DNA match probabilities should be presented alongside laboratory error rates, contrasting prosecution figures of 1 in millions to 1 in trillions with estimated laboratory error rates of 1 in 50 to 1 in 200
• Judge Ito ends the day with a tribute to Philadelphia Inquirer journalist Robin Clark, a trial regular and Pulitzer Prize nominee who died in a car accident over the weekend