Peter Neufeld conducted an extended cross-examination of Dr. Robin Cotton, challenging Cellmark’s procedures, controls, evidence handling, and proficiency testing. He elicited testimony that LAPD did not send substrate-control swatches for items 47, 48, 50, and 52; that Cellmark did not run reagent blank controls during the initial extraction of items 49 and 50; that Cellmark’s protocol required an inconclusive result when a reagent blank failed; and that Cellmark had not used blind external forensic proficiency tests during six years of proficiency testing. He also examined false positives from 1988 and 1989 and compared the estimated contaminant quantity from the 1989 event with Cotton’s estimate for item 52. On redirect, Cotton testified that roughly 104 proficiency tests covering 466 samples from 1990 through 1993 produced no additional false positives or incorrect exclusions, and she offered conditional explanations for differing degradation among samples. On recross, Cotton agreed those degradation hypotheticals would not apply if the items were processed at different times, though she did not know the actual LAPD processing dates.

• Peter Neufeld conducted an extended cross-examination of Dr. Robin Cotton
• Neufeld elicited testimony that LAPD did not send Cellmark substrate-control swatches for items 47, 48, 50, and 52
• Neufeld elicited testimony that Cellmark did not run reagent blank controls during the initial extraction of items 49 and 50
• Cellmark had conducted or received no blind external forensic proficiency tests during its six years of proficiency testing
• Neufeld exposed Cellmark's two false positive DNA matches from 1988-1989 CACLD proficiency testing
• Defense established that item 52's DNA quantity (25-50 nanograms) fell within the same range as the contaminant in the 1989 false positive
• Cotton testified that only two people in Cellmark’s African-American database had been typed at all five loci; on recross she confirmed that both were typed like Simpson across all five loci