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ST. LOUIS, MO (KTVI)-The St. Charles County Cyber Crime Unit continues investigating hidden bathroom videos and a porn web site that was operated by a police officer. Former Chesterfield police officer David Cerna will face a grand jury in Clayton, MO in July. He is being held in the St. Charles County jail facing invasion of privacy charges in two counties.

Cerna, 33, reportedly told detectives exactly how he recorded men using the restroom and then posted that video to a porn site. A Fox Files investigation into a hidden camera in the men’s room at a Chesterfield gas station led back to the officer.

Previous Story: Chesterfield police officer accused of recording restroom patrons, posting to porn site

Chesterfield Police Chief Ray Johnson said former officer Cerna told detectives that he put the camera in the bathroom right after his shift.

“He indicated that he would place it and then go back in about two hours [later] when the battery ran down.”

The hidden camera was placed directly above the toilet. When FOX 2 found this bathroom, it was immediately obvious where the camera was: inside the vent fan. The grate could easily be taken off and the camera placed inside.

On the porn site with bathroom videos, a web surfer asked “what kind of camera do you use?” Cerna responded, “Just a simple iPod touch.”

While it’s sad that you even have to look for this, FOX 2 will tell you have you can spot a possible camera the next time you use the bathroom. By simply shining a flashlight from your smart phone at the vent grate, a hidden camera’s location will easily be revealed.

Rob Cheney, who was secretly recorded on one of the bathroom videos, told us he’s now checking.

“I’m weird about going to the bathroom as it is,” says Cheney. “So now you know if I have to go I’ll go, but I’ll be looking around the walls, that’s for sure.”

Cerna faces three felony invasion of privacy charges so far, based on victims police have been able to identify. They expect more. Cybercrimes is now looking to see if the suspect took hidden bathroom video of any children.

Police Chief Johnson says, “We do believe that’s a possibility. It’s very likely depending on what times and how long of a period he had the camera in place that a young child may have been on there. At this point we have not seen any evidence of that.”

Again, Cerna’s case goes before a St. Louis County grand jury in July. The prosecutor’s office is also looking at cases Cerna handled when he was still a police officer to see if they’re in jeopardy. A spokesperson said they’ve so far found three drug cases and a stealing case they’re reviewing.