SALT LAKE CITY — Typically, voyeurs are male and they seek out adult female victims.

In that respect, the evidence seized in connection to the arrest of Steven Powell, father-in-law of missing Utah mother Susan Powell, is atypical, says Donald Strassberg, professor of psychology at the University of Utah. 

Steven Powell, 61, has been charged by charged by Pierce County, Wash., prosecutors with 14 counts of voyeurism and one count of possession of depictions of minors engaged in sexually explicit conduct in the second degree.

The charges against Powell were based on images of two children in various states of dress, including depictions of the children using the toilet, according to a probable cause statement. "Some of the images were of Susan Powell, but many of the images were of other females."

"That combination is less typical than voyeurs in general," said Strassberg in an interview Friday.

As a group, voyeurs tend to be a "bit more compulsive" and may not think through potential consequences of their actions.

However, the behavior of most voyeurs does not escalate beyond "peeping," Strassberg said. 

"The vast majority never even try to have contact with the people they've been spying on," he said.

The evidence seized in the case against Steven Powell goes beyond voyeurism because many of images involve pre-pubescent children in various stages of undress and while using the toilet.

"Most voyeurs have no interest in seeing this," he said.

Voyeuristic habits generally start during a male's teen years and may go unchecked for decades. "It tends to be fairly chronic pattern unless they get caught. They would have never caught this gentleman if they were not looking for evidence in a related case."

According to the probable cause statement, one detective noted that the images seized were neatly organized and labeled.

"That's not uncommon," Strassberg said. "He's a collector, not just a perpetrator. I'd be very surprised if he didn't go back and look at them quite often."

The odds suggest someone who is a voyeur is not likely to have committed a crime of violence, the professor said.

"If I'm looking at people of interest and now I learn someone has a deviant way of relating to other people, it certainly wouldn't make me less interested in this person,"  Strassberg said.

Susan Powell, of West Valley City, has been missing since December 2009. Her husband, Josh Powell, has long been considered a person of interest by authorities.