Defense forensic toxicologist Dr. Fredric Rieders testified that EDTA—the anticoagulant preservative found in blood collection tubes—was detected in evidence from Nicole Brown Simpson's back gate and the defendant's sock, supporting the defense theory that blood was planted from preserved samples. Rieders testified that EDTA levels were approximately 1,000 times higher than dietary sources could produce, strongly suggesting the source was a purple-topped blood collection tube. Prosecutor Marcia Clark launched a vigorous cross-examination, attacking Rieders' methodology, exposing errors in source materials, and impeaching his credibility with a prior case where his forensic conclusions failed independent scrutiny. The court ruled on multiple evidentiary disputes throughout the day, excluding photodegradation and dietary EDTA theories while allowing core testimony.

• Court allowed Dr. Rieders' EDTA testimony despite prosecution's exclusion motion.
• Rieders testified EDTA was present in sock (Q206) and back gate (Q204) evidence.
• Rieders criticized FBI's EDTA testing methodology for lacking internal standards and validation studies.
• Court excluded photodegradation and dietary EDTA absorption theories due to insufficient scientific foundation.
• Rieders testified EDTA levels were roughly 1,000 times higher than diet alone could produce.
• Clark exposed potential typo in EPA report Rieders relied upon during cross-examination.
• Clark elicited damaging admission that FBI Agent Martz's own unpreserved blood showed similar EDTA levels.
• Clark impeached Rieders with Sconce poisoning case where his prior forensic findings were contradicted by sophisticated testing.
• Judge issued stern warning to Clark for editorial commentary during cross-examination.
• Court negotiated early Friday 8:30 AM start to accommodate Rieders' medical appointment and Vienna trip.