Peter Neufeld served as a defense attorney specializing in DNA evidence, working alongside Barry Scheck and Robert Blasier to challenge the prosecution's forensic case. He appeared across dozens of trial days and conducted aggressive cross-examinations for the defense — systematically challenging LAPD criminalist Andrea Mazzola's credibility by exposing contamination captured on the prosecution's own video, contradictory sworn testimony about evidence collection, and repeated protocol violations. Neufeld brought the same methodical intensity to the defense's DNA experts, catching prosecution statistician Dr. Bruce Weir in computational errors that biased results against Simpson and extracting concessions from Cellmark director Dr. Robin Cotton about missing controls and degraded evidence storage. His work formed the backbone of the defense's contamination and unreliability narrative, turning the prosecution's scientific evidence — meant to be its strongest asset — into a liability.