Prosecutors have charged the prime suspect in Stacy Peterson's disappearance with a felony weapons offense.
Drew Peterson, 54, turned himself in to Illinois State Police Wednesday, after a judge issued a warrant for his arrest.
The former Bolingbrook, Ill., police sergeant was processed and then released later in the afternoon after one of his son's posted bail.
Peterson walked into the police station shortly before 1 p.m. CDT, accompanied by his attorney, Joel Brodsky. He was taken shortly afterward to the Will County jail.
His son posted $7,500, or 10 percent of a $75,000 bond, to secure his release pending trial.
The weapons charge, a class three felony, stems from the fact that one of the 11 guns authorities seized Nov. 1 in their investigation into Peterson's fourth wife Stacy's disappearance is shorter than allowed by Illinois law, according to Brodsky. Specifically, the rifle's barrel doesn't meet the 16-inch length requirement.
Brodsky said the weapon in question is an AR-15 semiautomatic assault rifle that Peterson used while he was a police sergeant.
Peterson claimed he legally owned the rifle as an officer, and the law only pertains to civilians.
If convicted of unlawful use of a weapon, Peterson faces up to five years in prison. A court date hasn't yet been scheduled.
Peterson has been trying for months to convince a judge to order the Illinois State Police to return the seized weapons. The judge already ordered police to return Peterson's vehicles and other belongings.
A court hearing was scheduled for Thursday on a proposal from Brodsky that ownership of the guns be transferred from Peterson to his adult son.
Stacy Peterson, 23, was reported missing Oct. 29, 2007, after she failed to show up at a friend's house and her family couldn't reach her. Drew Peterson said he last spoke to her the previous night. He has maintained that he had nothing to do with her disappearance, saying she ran off with another man and is in hiding.
Police are also investigating the death of his third wife, 40-year-old Kathleen Savio. She was found dead in a dry bathtub in 2004. Her death was initially ruled an accident, but when Stacy Peterson disappeared, Savio's body was exhumed. An additional autopsy determined she was the victim of a homicide.
Documents show that Savio had filed for an emergency order of protection from her husband, writing in the file that "he wants me dead and if he has to he will burn the house down just to shut me up."
Peterson retired from the police force after his fourth wife vanished.
Authorities have said they believe that Stacy Peterson is dead, and extensive searches have been conducted in forests, marshes, lakes and other areas in suburban Chicago.
The Associated Press contributed to this report.