The mother of two was married to former Bolingbrook Police Sergeant and convicted murderer Drew Peterson.
Despite extensive searches, she has never been found. Drew Peterson claims Stacy ran off with another man, leaving her children behind.
FBI, IL State Police search Lockport canal for Stacy Peterson's body, sister says
Stacy's sister-in-law, Norma Peterson, spoke about the case Thursday night.
"We loved Stacy," Norma Peterson said. "We miss her. She was a part of our family. I just know, that this beautiful young woman behind me would not leave her children, family meant everything to her and that she would not willingly leave this family."
Drew Peterson is a person of interest in Stacy's disappearance, but he has not been charged with a crime. He is in prison for the murder of his third wife, Kathleen Savio.