Barry Scheck launched a sustained and methodical attack on the LAPD DNA laboratory's credibility and procedures during cross-examination of criminalist Collin Yamauchi. Scheck established that Yamauchi had only six months of casework experience before the Simpson case, that the lab lacked proper PhD supervision, that proficiency testing was not truly blind, and that Yamauchi rushed through processing 23 samples in a single day despite guidelines recommending a limit of 15. The day ended with Yamauchi ordered to review discrepancies in validation study records over the weekend before resuming testimony Tuesday.

• Scheck established Yamauchi had only ~6 months of casework experience before the Simpson case
• Lab supervisor Matheson testified that his subordinates knew more DNA than he did, establishing lack of expert oversight
• Scheck exposed that proficiency tests were not truly blind — analysts could read each other's results
• Yamauchi processed 23 samples in a single day (June 14-15, 1994) despite Amplitype user guide recommending ~15-sample limit to prevent contamination and mix-ups
• Discrepancies found between LAPD validation study records and actual analysis sheets
• Juror #12 removed for good cause, replacement drawn by lot
• Yamauchi directed to review and confirm validation records over the weekend