After a week of seeing defence witnesses crumble under cross-examination, OJ Simpson's defence team has begun to attach some credibility to the contention that he was framed by the police.
Dr Frederic Rieders, a forensic toxicologist, testified on Monday that levels of preservative retrieved from the bloody socks in Mr Simpson's bedroom and on the rear gate at the murder scene exceeded those commonly found in blood.
In what has been the strongest defence evidence yet to support the conspiracy theory, Dr Rieders suggested that the preservative, EDTA, could have come from the test tubes used to store samples of Nicole Simpson's blood.
Defence lawyers contend that the socks were contaminated with a sample of Mrs Simpson's autopsy blood after the killings and the gate blood came from a sample Mr Simpson provided the day after the killings.
EDTA is a naturally occurring anti-coagulant used by police laboratories to preserve blood samples. Dr Rieders testified that no person carries the levels found in Mrs Simpson's blood on the socks.
The prosecution contended that Dr Rieders had misread a report from the Environmental Protection Agency and that humans have much more EDTA than he said. If that were true, he countered, "people would be bleeding to death all over the place".
The testimony came as relief for the defence, which has recently been stung by counter-productive witnesses and evidence. First, Mr Simpson's doctor was forced to concede that although suffering from severe football injuries the defendant would have been able to pull his ex-wife's head back and cut her throat.
Jurors then heard Mr Simpson joke about punching one's wife in an exercise video he made several weeks before his ex-wife's murder. In the workout, Mr Simpson could be seen shadow-boxing. "Get your space in if you're exercising with your wife, if you know what I mean," he said, adding with a smile: "You can always blame it on working out." Prosecutors argued that the remark reflected his attitude toward his wife.
In another defeat for the defence, Judge Lance Ito denied a request for a hearing on the issue of jury-targeting. The judge ruled there was no evidence that jurors had been targeted for dismissal.
A tow-truck driver who testified that he did not see blood stains in the white bronco was discredited by evidence that he had stolen receipts from the vehicle. A police photographer said there were no socks when he videotaped Mr Simpson's bedroom. But it was later shown that the socks had already been removed by a criminologist, Dennis Fung.
The defence is expected to continue its attack on blood evidence with a blood-splatter specialist who will testify that a red substance on the socks was smeared there in a frame-up.