Peterson, the shift commander that night, reportedly granted permission to an officer to chase a suspect, who crashed into another vehicle after speeding nearly 100 miles per hour, opening the department to a potential lawsuit.
Although law enforcement and the public suspected foul play, she has never been found, and Peterson has not been charged in her case.
The coroner had ruled the cause of death an accidental drowning.
"Drew Peterson went to being a person of interest to clearly a suspect," said Illinois State Police Capt.
Family members long have suspected that Savio didn't drown accidentally, Melissa Marie Doman, Savio's niece, said. Drew Peterson recently told reporters that he believes his wife is alive and said he is being treated unfairly in this case.
"I am all for it, along with the rest of my family, because something just was never right," Doman said. Drew Peterson divorced Kathleen Savio, but financial issues hadn't been finalized when her body was found in her bathtub in 2004.