Ted S. Warren, AP
Steven Powell, the father-in-law of missing Utah woman Susan Powell, appears in Pierce County courtroom, Friday, Sept. 23, 2011, in Tacoma, Wash. Powell, who was arrested Thursday, plead not guilty to charges of voyeurism and possession of child pornography. (AP Photo/Ted S. Warren)
Both (girls) deserve to see justice from this court and deserve to see the defendant held accountable for his repeated violations of their privacy. —Prosecutor Grant Blinn

TACOMA, Wash. — Prosecutors will ask a judge to sentence Steven Powell to 10 years in prison for 14 counts of voyeurism, according to court documents.

A jury convicted Powell, the father-in-law of missing West Valley City mother Susan Cox Powell, on the charges May 16. As part of the investigation into Cox Powell's disappearance, police searched Steven Powell's home and seized thousands of photographs of women and girls.

He was accused of taking thousands of pictures of two girls who were his neighbors starting in 2006. The girls were 8 and 10 at the time. They are now 13 and 15 years old.

He videotaped and photographed them from his house — just 40 to 50 feet away — by looking into their bathroom through an open door.

Though each voyeurism count carries a maximum penalty of up to five years in prison, the average penalty range for this type of crime is 43 to 57 months in prison.

Prosecutor Grant Blinn said that he would seek a stronger sentence and did so in a memorandum filed earlier this week in Pierce County Superior Court.

Blinn said that while Powell had no criminal history, he would ask that the judge find he deserved an "exceptional sentence aggravator" that would allow for 60-month sentences. Blinn is asking that two 60-month sentences be handed down and that Powell be ordered to serve each consecutively.

"Since the defendant in this case was convicted of 14 counts of voyeurism, a standard range sentence of 43 to 57 months would allow 10 of his convictions to go unpunished," Blinn wrote. "Most importantly, a standard range sentence effectively allows the defendant's crime against one of his victims go unpunished."

The prosecutor said Powell had two victims who were repeatedly victimized. Blinn added that they were victimized in their own home, where they believed they were safe from voyeurs.

"Both (girls) deserve to see justice from this court and deserve to see the defendant held accountable for his repeated violations of their privacy," Blinn wrote.

A phone message left with Powell's attorney, Travis Currie, was not returned Thursday.

Images of Cox Powell, many taken without her knowledge, were among those found by investigators, but were not included at trial.

Cox Powell, a 28-year-old mother of two, has been missing since Dec. 6, 2009. The night before she was reported missing, Josh Powell, Steven Powell's son, said he took their two young children camping in single-digit temperatures in a remote part of Tooele County in the middle of the night. When he returned a day and a half later, he said his wife was gone.

Josh Powell was named a person of interest in the case, but was never arrested. He later moved into his father's Washington home.

Josh Powell and his two sons Charlie, 7, and Braden, 5, died Feb. 5 when Josh Powell set fire to his Graham, Wash., home.

Prosecutors have said they will not consider a more lenient sentence against Steven Powell in exchange for information about Cox Powell's disappearance.

Steven Powell is scheduled for sentencing June 15.