PORTLAND – The man arrested this weekend for assault at a Biddeford bar gave a phony name, but the “Geisinger” tattoo in big letters across his back led police to conclude he was Jonathan Geisinger.

But officials at the Cumberland County Jail maintained that Geisinger, 24, was asleep in his room at the jail’s prerelease center, finishing his 180-day sentence for assault.

They roused the inmate about 2 a.m. Sunday just to be sure, and discovered his tattoos did not match those on file for Geisinger.

When jail officers returned to collect Geisinger’s stand-in, they found he had cut through the screen of his second-floor window and escaped.

Now, the jail is adopting new security measures to make sure that people who sign in after a work-release or supervised community work crew assignment are who they say they are.

“I spend a lot of energy figuring out how to keep people from breaking out,” said Sheriff Mark Dion. “I didn’t anticipate we’d have one breaking in.”

The jail’s Community Corrections Center offers work-release privileges to well-behaved inmates who are close to finishing their sentences.

Officials believe Geisinger swapped places with his stand-in the day before he was arrested in the bar fight.

The duty officers at the prerelease center change with different shifts and don’t necessarily recognize the inmates by name, Dion said. Typically, the officers do a head count to make sure each inmate is in his room when the facility is locked and lights doused at 11 p.m.

The jail now will require each person checked in to be matched with a photograph. Officers will conduct sporadic checks throughout the night.

In addition to four counts of assault resulting from the fight at the 50s Pub, Geisinger now faces a charge of felony escape. He had been due to get out of jail in May.

The man who returned to jail in Geisinger’s place also may find himself in hot water with the law.

“When we bring this other individual to the barn, and we will, we’re going to charge him with aiding and abetting an escape,” Dion said. “If it was his intent to be here, we’d like to cement that intent with a longer stay.”