DENVER -- State law mandates that police departments post warning signs to let motorists know when photo radar is in use.

But one motorist told 7NEWS that he has seen several photo radar vans operating on University Boulevard, or on First Avenue without the required sign.

“I think that if I have to obey the law, the Denver Police Department has to obey the same laws,” said Bill O’Neil, an Aurora resident who works in the Cherry Creek North business district.

O’Neil said he was driving westbound on First Avenue on Jan. 20, when he spotted a photo radar van at Franklin Street.

“I didn’t see a sign, so I drove back around got out my cell phone and used the camera to start recording at University,” O’Neil said. “I recorded all the way past the van. There was no sign.”

When asked if Denver police failed to set up a sign, department spokesman Sonny Jackson said, “No, that sign was actually there 367 feet from the van.”

But Jackson said the sign wasn’t on the same side of the road that O’Neil was aiming his cell phone.

“We’re all conditioned to think that the sign is going to be on the same side as the van. It can be wherever it’s most visible,” Jackson said.

In this case, Jackson added, the sign was in the median on the left side of the road.

“There was less chance of turning traffic obscuring the sign in the median,” Jackson said.

O’Neil told 7NEWS that he made his cell phone recording at 11:30 a.m.

Jackson said Police Department logs show that the technician was operating the van from 10:10 a.m. until 11:15 a.m.

“She was likely powering down the equipment and may have already taken down the sign when the video was shot,” Jackson said. “But the sign was in place when the van was in operation.”

When told that police said the sign was on the left side of the road, O’Neil chuckled and said, “I don’t know what to say.”

Jackson said there’s a checklist that operators go through to set up the van. He said they’re very meticulous about it because they don’t want the tickets to get thrown out in court.