On Monday, Fredric Rieders, a 73-year-old defense toxicologist, gave little ground to prosecutor Marcia Clark as she challenged his credentials, his methods and his conclusions.

``That's absurd!'' he responded to some of her insinuations. ``You're absolutely incorrect.''

Rieders said EDTA was present on crucial murder evidence: the sock and the back gate of his ex-wife's condominium.

The police lab stored blood samples including Simpson's blood and that of his slain ex-wife in vials with EDTA added to prevent clotting. That blood was then tested against evidence collected in the case.

If police wanted to frame Simpson, defense attorneys say, all they had to do was smear some of the blood samples on evidence to incriminate Simpson.

Ms. Simpson and Goldman were found slain outside her condo on June 12, 1994. Simpson, charged with the murders, maintains he is the victim of a police conspiracy and is not the killer.

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