DNA analyst Gary Sims from the California Department of Justice testified extensively about RFLP and PCR testing, presenting statistics showing odds of 1 in 21 billion for Nicole Brown Simpson's blood on sock A. Harmon also used scientific literature and redirect hypotheticals to elicit Sims' view that contamination was detectable and unlikely under proper protocols and that the sequence of substrate controls argued against cross-contamination. Under intense cross-examination by Barry Scheck, Sims made concessions about proper laboratory contamination protocols—sample separation, material handling, cleaning procedures—while Scheck methodically suggested LAPD failed to follow documentation protocols and highlighted that Sims processed 21 Bronco samples simultaneously, above the guide's recommended batch size. The defense developed its core contamination theory: LAPD technicians processed known suspect samples alongside unknown crime scene samples, creating a cross-contamination risk that could explain the DNA results without proving guilt.

• DNA analyst Gary Sims testified to 1 in 21 billion match odds for Nicole's blood on sock A
• Sims presented PCR frequency statistics ranging from about 1 in 520 to 1 in 6 million for blood evidence from multiple locations
• Barry Scheck methodically cross-examined Sims and extracted admissions about best laboratory contamination practices
• Scheck revealed Sims processed 21 Bronco samples at once, exceeding the Amplitype guide's recommended batch size of 15
• Defense exposed documentation failures: LAPD bindles bore pencil initials instead of required ink, lacked proper technician signatures
• Judge overruled Scheck's discovery objection regarding FBI population study but sustained objection to DNA projection hypotheticals
• Newspaper article slipped past jury screening but was immediately reported by diligent juror and deemed harmless
• Two media attendees banned from courtroom after jurors complained about constant disruption