Day 64 was dominated by the prosecution's direct examination of LAPD chemist Gregory Matheson, who testified extensively about forensic evidence collection procedures, contamination science, and chain of custody protocols. The prosecution elicited Matheson's testimony that improper collection techniques cannot alter blood type markers, presenting it as a direct rebuttal to defense contamination arguments. Pre-trial motions centered on exhibit admissibility and evidentiary disputes, while one juror was replaced mid-day.

• Juror #2 excused for good cause; alternate #1427 selected as replacement.
• Prosecution began extensive direct examination of Gregory Matheson, LAPD Chief Forensic Chemist, establishing credentials and expertise.
• Matheson testified about SID facility security, evidence collection procedures, and his own collection of blood from the Bronco console.
• Pre-jury dispute over characterization of EAP blood-typing results associated with Nicole Brown Simpson; court ruled issue went to weight, not necessarily admissibility.
• Prosecution used hypotheticals to establish that improper collection adds material but does not change genetic markers.
• A prosecution demonstrative concerning samples handled by the defense and a disputed testing implication prompted a heated dispute; the court deferred its ruling.
• Jury excused early (4:25 PM) due to exhibit dispute regarding People's 209 evidence disposition chart.