Dr. Robin Cotton, laboratory director of Cellmark Diagnostics, served as the prosecution's central DNA expert, spending six days on the stand in May 1995 — one of the longest stretches of any witness in the criminal trial. Guided by prosecutor George Clarke, she methodically walked the jury through the science of PCR and RFLP testing before presenting results linking blood evidence from the Bundy walkway, Rockingham foyer, Ron Goldman's boot, and a pair of socks, with population frequency statistics reaching as high as one in 6.8 to 530 billion. Defense attorney Peter Neufeld mounted an aggressive cross-examination, extracting admissions about missing substrate controls, absent reagent blanks, and the potential for degraded evidence stored in hot, unrefrigerated trucks to produce unreliable results. Cotton returned in the civil trial, where she was one of three DNA experts who testified about evidence tying Simpson to the crime scenes, his Bronco, and the victims' possessions.