05/16/2012 at 03:00 PM EDT
The father-in-law of missing mom Susan Powell was convicted Wednesday of voyeurism in Tacoma, Wash. Police uncovered surreptitious images of Susan and of disrobing girls who lived next door while investigating Susan's December 2009 disappearance
Steven Craig Powell, 62, was convicted of 14 counts of voyeurism after a weeklong trial that included testimony from the two girls, who were 8 and 9 when the incidents occurred in 2006, and are now 13 and 15.
He faces up to 70 years in prison.
Prosecutor Grant Blinn said in his closing arguments Tuesday that the girls were unaware that Powell was quietly photographing them through an open window. "They had no idea at the time that this defendant was lurking in the shadows of his own bedroom," Blinn said.
Susan's parents attended the trial in the hopes that Steve Powell might share anything he may know about their daugther's disappearance
Susan's husband Josh Powell, son of Steven and a person of interest in her disappearance, killed himself and the couple's two sons
on Feb. 5 by blowing up his rental house.