Was blood found on a sock inO.J. Simpson's bedroom and on a gate at the murder scene planted by police? Witnesses for the O.J. Simpson defense can't agree on the razor-thin strand of evidence that might support such a claim. Monday, Fredric Rieders, a forensic toxicologist, testified that the blood apparently contained EDTA, a chemical preservative used in crime analysis, which suggested that the blood could have been planted by someone with access to samples from the victims and the defendant. Today, FBI Special Agent Roger Martz -- who performed the analysis of the blood -- said Rieders essentially misrepresented his findings. "Those bloodstains did not come from preserved blood," Martz said under sharp questioning from defense attorney Robert Blasier. "I was able to prove that." But truth remains elusive:the defenseimpugned Agent Martz' objectivity, claiming that he was first recruited by the prosecution to prove there was no EDTA in the blood, and so did not conduct an impartial study.