The gun, a semiautomatic assault rifle, was one of 11 seized during a search of Peterson's suburban Chicago home Nov. 1, shortly after Stacy Peterson disappeared in late October. Authorities say the rifle barrel is too short under Illinois law.
Brodsky said that Peterson, now retired, was still a police officer when the weapon was seized and that officers are exempt from the length provision of the law.
Will County State's Attorney spokesman Chuck Pelkie would not say whether police are exempt from the law, but said the charge against Peterson is valid and appropriate.
"An illegal weapon might be put back on the street and we can't let that happen," Pelkie said.
Illinois State Police Sgt. Thomas Burek denied that the charge was an attempt to harass Peterson.
