Gregory Matheson, the LAPD crime laboratory's assistant director and chief forensic chemist, was one of the prosecution's key scientific witnesses. Called by prosecutor Hank Goldberg, he spent five days on the stand testifying about conventional serology results, evidence collection procedures, and chain-of-custody protocols, including his finding that a crime scene blood drop matched only O.J. Simpson's rare blood subtype. Defense attorney Robert Blasier's cross-examination extracted concessions about the lab's lack of accreditation, absent formal procedures, unrefrigerated blood storage, and approximately 1.5 milliliters of Simpson's reference blood that could not be accounted for — building blocks for the defense theory that evidence had been planted.