Dr. Robert Huizenga served as O.J. Simpson's personal physician and testified as a defense medical witness in July 1995, reporting that Simpson suffered from severe knee arthritis, rheumatoid arthritis, and other mobility-limiting conditions that the defense argued made him physically incapable of committing the murders. His examinations of Simpson on June 15–17 found no major injuries beyond pre-existing cuts on Simpson's left hand. Prosecutor Brian Kelberg subjected Huizenga to an extensive, multi-day cross-examination that exposed bias through letters discussing litigation strategy, attacked inconsistencies in his testimony, and used exercise videos and medical records to undermine the arthritis defense — pressing him so relentlessly on whether Simpson could have committed the killings that Huizenga admitted he had lost sleep over his answers. He returned in the civil trial, where plaintiffs used his testimony to establish that Simpson's fresh hand injuries were consistent with the June 12, 1994 murders.