Denise Brown, Nicole Brown Simpson's sister, was a key prosecution witness who provided emotionally powerful testimony about O.J. Simpson's pattern of abuse, control, and violence toward Nicole spanning from 1977 through 1993. Over multiple days in early February 1995, she described increasingly graphic incidents of physical and emotional abuse and was among the witnesses who recounted Simpson's frightening demeanor at his daughter's school recital on June 12, 1994 — just hours before the murders. The defense aggressively challenged her testimony, but her firsthand accounts helped the prosecution build its domestic violence narrative as a foundation for motive.