 The only possible scenario would be a mixture of two persons DNA being typed, Simpsons and the "Real Killer" if cross-contamination occurred, but only Simpsons was found.She admitted her tests cannot demonstrate how the blood got on Simpson's sock, meaning her tests do not refute the possibility the blood was planted.Criminalist Gary Sims of the California Department of Justice Crime Lab testified May 16 - 22, and again from May 31 to June 1, 1995.