Prosecution forensic evidence dominated Day 6, with serologist Greg Matheson presenting blood typing analysis that matched O.J. Simpson's rare PGM blood subtype while excluding both victims from a crime scene drop, appearing to exclude 99.57 percent of the population. Defense attorney Gerald Uelmen challenged Matheson's statistical methodology, arguing that its population data were non-race-specific and racially unrepresentative and introducing a mixture-blood scenario that Matheson said could yield approximately 40,000–80,000 potential matches in Los Angeles; on redirect, Matheson testified that both contributors would need the rare subtype, which neither victim had, and that the stain's profile was consistent with a single contributor. Medical Examiner Dr. Irwin Golden then testified to the fatal wounds inflicted on both victims, establishing cause of death with detailed clinical descriptions but declining to definitively identify a folding knife as the murder weapon.

• LAPD serologist Greg Matheson testified that crime scene blood drop item 49 matched O.J. Simpson's blood profile, statistically excluding 99.57 percent of the population
• Defense challenged Matheson's frequency calculations as relying on non-race-specific, non-random, and racially unrepresentative population data
• Matheson conceded that if the blood drop was a mixture from two people, approximately 40,000-80,000 people in Los Angeles could potentially match
• Medical Examiner Dr. Irwin Golden detailed the fatal neck wound on Nicole Brown Simpson—a single cutting wound severing both carotid arteries and damaging both jugular veins
• Dr. Golden testified about all sharp force wounds on both victims but declined to definitively identify a folding knife shown to him as the murder weapon