The ruling Wednesday is expected to further delay the trial, which was supposed to start in 2010, the Chicago Sun-Times reported.
The former Bolingbrook, Ill., police officer is charged with murder in the 2004 drowning death of his third wife, Kathleen Savio. The case, which was initially considered an accidental death, was reopened after Peterson's fourth wife, Stacy, disappeared in 2007, the Chicago Tribune said.
Peterson, 57, has been jailed since May 2009 on $20 million bail.
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