The Will County State's Attorney's Office contends the statements are crucial to their efforts to convict Peterson. Prosecutors claim Savio's friends said she was worried he might try to kill her.
The ruling essentially allows Savio to testify from the grave.
Stacy Peterson, the former officer's fourth wife, was last seen on October 28, 2007. Drew Peterson has never been charged in her disappearance.
"The court found that the State proved by a preponderance of the evidence that: (1) the defendant murdered Kathleen and Stacy; and (2) he did so with the intent to make them unavailable as witnesses," the decision states. "Thus, we also hold that the eight excluded statements are admissible under Rule of Evidence 804 (b) (5)."
Some legal analysts say the statements could become important elements in a case where there is very little physical evidence.
Among the possible evidence the court ruled is admissible are statements from Stacy Peterson's pastor in which she allegedly provided Drew Peterson with a false alibi the weekend Savio died. The coroner ruled her death was an accidental drowning in her bathtub. Prosecutors reclassified Savio's death as a homicide after they re-examined her body in 2007.
Peterson's attorneys insist they are not concerned about the ruling. They say the statements are unreliable and the judge could still refuse to allow them.
"It is still under the discretion of the court," said Steve Greenberg, Peterson's attorney. "The court can let them in or keep the statements out. If you look at the statements, none of them are really credible. Some of them, the state's attorney shouldn't use, because the judge found they aren't even reliable."
"The prosecution's case was a thin one, but it just got thicker," said Harold Krent of IIT Chicago-Kent Law School. "The prosecution is in much better shape today than it was yesterday."
The prosecutors now anticipate the case going to trial later this spring or summer.