Ever wonder why people wear a smock over their shoulders in mug shots from the Pima County jail?

They may be the only ones in Arizona and - maybe in the country - who briefly put on a uniform during the ubiquitous photo shoot.

But there really is no unusual story behind the use of these smocks, said Deputy Jason Ogan, a Pima County Sheriff's Department spokesman.

"We use the smock to give mug shots a uniform look, and that's pretty much it," he said. "Having something like that over their shoulders makes it easier to look at their faces, especially when having to look at many mug shots at once."

Pima County has been photographing detainees with blue smocks for about 15 years, Ogan said.

The smock is draped over the person's shoulders from front to back, covering the chest and most of the upper body.

Some mug shots show people wrapped in the smock in a cocoonlike way; others show the smock smoothly placed on the chest and thrown back over the shoulders.

The jail uses a smock in every photograph taken during booking, and it changes the garment every two to three days.

The smock also helps when people are put on a lineup, said Sgt. Steve Street of the Pima County jail.

"It makes it so if somebody puts your photo on a lineup, it looks like you're wearing a blue shirt," Street said. "It doesn't make you look like you're in jail."

Jail officials were not sure whether any other county jails used the smock. Ogan said he was unaware of any other county jail using the garment.

Photos from other Arizona county jails don't show smocks in mug shots.

Contact reporter Fernanda Echavarri at fechavar@azstarnet.com or 573-4224.