EVERETT — A former Monroe police sergeant spent much of Friday on the witness stand insisting there was nothing sexual about his hiding cameras in his bathroom in 2004 and secretly recording a 15-year-old babysitter while she undressed and used the shower.

Carlos Alberto Martinez told a Snohomish County Superior Court jury he was looking for evidence the teen was cutting herself, and he stopped the surveillance as soon as he was convinced there was no reason for worry.

Martinez also acknowledged that he developed a strong sexual attraction to the young woman. He said that didn’t happen, however, until she touched him when they rendezvoused at a Spokane motel in early 2007, about a month after she turned 18.

At the time, she was a senior in high school. Martinez was 52 and married.

Now 61, Martinez is charged with voyeurism and possession of depictions of a minor engaged in sexually explicit conduct, both felonies.

Prosecutors allege the videotaping was a crime because the former babysitter, now 26, was unaware Martinez was recording her, and that he created and kept the videos for years for his sexual gratification.

Although the trial has probed the defendant’s sexual connection to the young woman, the key questions in the case increasingly appear to focus on the reason Martinez made the recordings and how the former babysitter learned of their existence.

Martinez on Friday testified that he wasn’t sexually interested in the babysitter when he created the videos. Further, he said that he told her about them in July 2007, months after they’d begun having an affair.

Indeed, when that relationship ended in Texas in 2011, Martinez testified that he conducted his own research and concluded the statute of limitations had elapsed around any legal questions he could face over secretly recording a teenaged girl in 2004.

That’s one reason he was comfortable giving the tapes to the young woman, he said.

Although she testified about making other sexually oriented videos and photographs with Martinez, the young woman told jurors she didn’t know about the videos made when she was 15 until Martinez showed them to her in Texas.

She testified that she took them to police, in part out of disgust over Martinez sexually touching himself, with her present, while watching the recordings.

Martinez on Friday denied touching himself, but said the pair did watch the videos together and engage in sex that night.

Jurors already have heard how Martinez met the girl when she was 10 and he was teaching a drug-abuse resistance class at her elementary school.

She testified across three days about her confusion and guilt over sexual conduct she insisted began with Martinez improperly touching her when she was in her early teens in Monroe.

Under questioning by Everett defense attorney Mark Mestel, Martinez denied any sexual activity with the girl until she reached 18.

He said that when he told her about the tapes in 2007 she asked to see them and “she seemed flattered.” A few days later she asked to borrow his video camera, and told him she was going to make him a “better tape,” Martinez said.

Jurors were shown a recording Friday of the young woman taking a shower. Martinez said she gave it to him in summer 2007 and suggested he use it for his sexual gratification.

The defendant bridled when deputy prosecutor Lisa Paul asked him to describe the sexually explicit videos and photographs of the young woman he’d collected over the years.

“I wouldn’t call it a collection,” he said.

She then began showing Martinez snapshots of his former girlfriend at different ages: 22, 18.

What was it about her that he found attractive?

“She liked me,” Martinez testified.

Well, she liked him when she was 10, 13 and 15, right?

That’s true, Martinez told the prosecutor, but he insisted nothing improper happened.

What, Paul asked, did he find physically attractive about the young woman?

Martinez said she was in shape. She had a lot of energy. He also noted that she had long hair and pale skin.

Paul showed him a photograph. She said it was of the girl, taken at 15.

The former babysitter smiled at the camera, looking much as she had when she testified earlier in the week.

Martinez was expected to return to the witness stand to face more questioning Monday.

Scott North: 425-339-3431; north@heraldnet.com. Twitter: @snorthnews.