CHICAGO (AP) -- Walter Unbehaun has spent nearly all of his adult life behind bars, so it's not surprising that he faces sentencing Thursday for yet another crime, a bank robbery last year. His reason for robbing the bank is surprising, though: He was homesick for prison. The 74-year-old high-school dropout and part-time bathtub repairman probably isn't the first long-term convict to find he prefers being barked at by guards to life on the outside, which has its own demands. But living alone and feeling unhappy, Unbehaun decided to change his situation by committing a crime in order to get caught. On Feb. 9 of last year, he entered a Chicago-area bank with a cane but no disguise, displayed a revolver in his waistband to a teller and told her softly over and over, "I don't want to hurt you." With $4,178 in loot, he then drove to a nearby motel and waited for police to arrive. Confronted by authorities in the motel parking lot, the bald, portly Unbehaun dropped his cane, raised his hands and startled police by his apparent joy at getting nabbed, according to detailed court filings by both his attorney and the lead prosecutor in his case. "Unbehaun stated he wanted to do something that would guarantee that he would spend the rest of his life in prison," an FBI affidavit said. "He knew robbing a bank with a loaded gun would accomplish that." One officer observed, "(He) was happy to be going home to prison." The judge in Chicago who will sentence Unbehaun faces a dilemma, prosecutor Sharon Fairly pointed out in one filing: Sending Unbehaun to prison would be more of a reward than a punishment for him, but setting him free would risk him trying to commit another crime. "Did the system fail Mr. Unbehaun? Or was his inability to stay out of jail the result of his own free will?" Fairly asked. "We may never know. But what we do know, clearly, is Mr. Unbehaun lacks the desire to lead a law-abiding life outside of prison walls." Even if his age and infirmity might seem to invite leniency, that "is arguably offset by his lengthy and violent criminal history," Fairly said. She didn't point out that keeping Unbehaun in prison would cost taxpayers. On the other hand, setting him free could send the wrong message to other would-be bank robbers. Unbehaun first went to prison at age 23 for transporting a stolen car, and his criminal record includes more than half a dozen convictions for everything from home invasion to -- ironically -- escaping from prison. Media accounts from 1970 describe how Unbehaun kidnapped a 19-year-old girl and left her bound to an Ohio motel bed as fled the state in her car. For that, he was convicted of kidnapping and sentenced to 25 years. His most recent decade-long prison term, which was for a bank robbery, ended in 2011. Unbehaun pleaded guilty in September to the 2013 bank robbery in the Chicago suburb of Niles and faces a maximum 30-year prison term. Prosecutors asked for a sentence of about seven years. In his presentencing filing, defense attorney Richard McLeese called on the judge to show Unbehaun mercy. "An individual driven to commit bank robbery so that he can return to prison is, we submit, less culpable than someone who acts simply out of greed," McLeese said. A three year sentence, he argued, would be appropriate. In a brief letter filed to the judge last week, Unbehaun didn't withdraw his wish to go to prison. But he did write, "I wasn't thinking straight" and "I don't want to die behind bars." Unbehaun was divorced twice and his third wife died. But it's not as if no one extended the childless widower a helping hand. Following his 2011 release, his sister and her husband bought Unbehuan a trailer home in Rock Hill, S.C., the couple said Wednesday. Bored and lonely, Unbehaun spent his days watching television or drawing, and in a court filing he compared his life at the trailer park to living in a prison isolation "hole." "We tried to help him and do as much as we could, but it didn't work out," Unbehaun's sister, Darlene Kellner, said in a phone interview from South Carolina. "It is a sad story." At pre-trial hearings, Unbehaun sat in a wheelchair wearing orange jail garb, appearing attentive and at ease. McLeese said mild dementia may have contributed to his client's decision to rob his way back into prison. "No matter," he said. "It is difficult to imagine a more desolate set of circumstances than one in which the only possible alternative an individual would envision was life behind bars."