An aging ex-con who deliberately got caught robbing a bank so he could go back to prison should have his wish fulfilled, federal prosecutors say.

Walter Unbehaun, 73, spent most of his adult life behind bars, and was apparently so unhappy living as a free man that he stuck up the BMO Harris Bank at 7077 W. Dempster St. in north suburban Niles on Feb. 9 with the intention of being caught, according to the Chicago Sun-Times.

He told FBI agents he “wanted to go back to the only life he knew — prison life,” according to court papers filed this week by the U.S. Attorney’s office.

Prosecutors want U.S. District Judge Sharon Johnson Coleman to lock him up for six to eight years, a sentence they acknowledge “would seem to be rewarding him for precisely the behavior we seek to deter.”

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But they say Unbehaun’s willingness to stick up a bank, even though he walks with a cane and has had hip-replacement surgery, shows just how determined he is to stay behind bars, making him a public danger at an age when most criminals have settled down.

“Did the system fail Mr. Unbehaun?,” prosecutor Sharon Fairley wrote in the filing. “We may never know. But, what we do know is, clearly, Unbehaun lacks the desire to lead a law-abiding life outside of prison walls.”

He was was arrested outside a North Chicago motel by FBI agents and Niples police the day after the robbery. Agents received tips from people who had seen media coverage of the robbery, the FBI said at the time.

A federal criminal complaint charging one count of bank robbery allegeds that during thge robbery, Unbehaun told the teller, “This is a hold up. I have nothing to lose. Give me the money in the drawer.” He then opened his jacket to show a handgun in the waistband of his pants.

He told the teller, “I only have six months to live and have nothing to lose. I don’t want to hurt you,” the complaint said.

Unbehaun, of Rock Hill, S.C. — who has multiple convictions for bank robbery, car theft, home invasion, unlawful restraint, armed robbery, theft, unauthorized use of a weapon and armed violence going back to 1963 — is due to be sentenced next month.

His attorney did not return calls seeking comment.

Copyright SunTimes