Day 125 centered on the bloodstained socks, with defense bloodstain expert Professor Herbert MacDonell testifying that ankle stains were consistent with the socks being planted rather than worn during the murders. Prosecutor Marcia Clark delivered a devastating cross-examination attacking MacDonell's methodology, credibility, and qualifications, establishing critical discrepancies between his written report and trial testimony. Late in the day, Johnnie Cochran dropped a bombshell revelation: confidential Mark Fuhrman tapes contained racial slurs and discussions of fabricating evidence, potentially undermining police credibility on the stand.

• KNBC reporter Tracie Savage testified about confidential sources for the DNA leak story, invoking journalist shield law protections
• Defense expert Professor Herbert MacDonell testified ankle bloodstains on sock 13-a were consistent with artificial planting rather than being worn during crimes
• Prosecutor Marcia Clark cross-examined MacDonell, exposing discrepancies between his written report describing the stain as a 'swipe' and trial testimony calling it a 'compression'
• Johnnie Cochran revealed Mark Fuhrman confidential tapes contain racial slurs and discussions of fabricating evidence—termed a potential 'bombshell' for the defense
• Judge Ito allowed Thano Peratis's prior testimony on blood draws to be admitted despite prosecution objections about foundation
• Defense moved for sanctions against Clark for falsely stating the prosecution never received MacDonell's notes from the April 2 sock examination