The judge in Drew Peterson's first-degree murder trial ruled against declaring a mistrial Thursday after defense attorneys tried to show prosecutors deliberately entered testimony barred in advance of the trial.

"The defendant's ability to receive a fair trial was not extinguished at this time," Judge Edward Burmila told the court. He said he would not strike down testimony from the second witness, but will write a "cautionary instruction," which may indicate that he will toss out testimony about a bullet found in a neighbor's driveway.

Steven Greenberg, Peterson's attorney, had earlier requested a mistrial because he said prosecutors are trying to build their case around the supposed fear Kathleen Savio, his client's third wife, lived in at the time of her death.

A furious Burmila admonished prosecutors Wednesday after the second witness in just their second day of testimony began talking about finding a .38-caliber bullet on his driveway.

Thomas Pontarelli, a former neighbor of Savio's, hinted in his testimony that Peterson may have planted it there to intimidate him.

More On This...

"They're (prosecutors) trying to show the fear Savio lived in," Greenberg told the court Thursday. "They want to make this all about her fear. Her fear is inadmissible."

Peterson, meanwhile, appeared in court Thursday wearing a grey jacket and black pants. Greenberg pressed the judge for a mistrial with prejudice, which would have meant his client would walk free.

On Wednesday, Burmila wondered aloud about whether the testimony made Peterson appear menacing in jurors' eyes and undermined his ability to get a fair trial.

Peterson, who was a police officer in the Chicago suburb of Bolingbrook, has pleaded not guilty to first-degree murder in Savio's death. He also has said he wasn't responsible for his fourth wife's disappearance.

The legal snafus are just the latest twist in a case long plagued by problems, including a botched initial investigation that left prosecutors with no physical evidence and forced them to rely heavily on normally prohibited hearsay.

The mistrial decision was handed down before prosecutors presented the most delicate of the hearsay evidence, including Savio's alleged remarks to others about Peterson threatening to kill her before her body was found in a dry bathtub at her Bolingbrook home.

The Associated Press contributed to this report