PORTLAND – Barry McCarthy was isolated in a maximum-security cell at the Cumberland County Jail when he called police with an offer.

His subsequent confession to the Jan. 20, 1999, murder of Ila Boyle in Orland was upheld Monday by the state supreme court in a ruling that finds confessions admissible if they are made with the hope – but not the promise – of leniency.

About a month after Boyle’s gruesome death, McCarthy told police he was willing to talk, even without his lawyer present, if he could be transferred to Maine State Prison in Thomaston.

Later that day, investigators interviewed him. His lawyer was not told about the interview, but McCarthy was read his Miranda rights.

State police Detective David Preble told the defendant, “I think you’ve been around long enough to know that ahh, usually cooperation gets a little bit of favoritism, but I cannot guarantee you that. OK?”

McCarthy then admitted that in a fit of rage after sex he strangled the 36-year-old he had met in an Ellsworth homeless shelter. Prosecutors say McCarthy later used a tire rim to crush Boyle’s skull.

In November 2001, McCarthy pleaded guilty to murder, on condition that the case go to trial if the Maine Supreme Judicial Court threw out his confession. He currently is serving a 45-year sentence.

McCarthy’s appeal raised the question of whether his confession was voluntary or induced.

During the videotaped interrogation, Preble repeatedly told McCarthy that he could not promise him a transfer to the Maine State Prison. But he also said, “You know as well as I do that your chances of going to the prison are probably real good.”

The high court found that such an insinuation is acceptable as long as no promise of leniency is made. Assistant Attorney General Donald Macomber said the court was correct to rule that McCarthy confessed voluntarily.

But Jeffrey Toothaker, McCarthy’s attorney, said the court’s ruling will allow authorities to subvert the intent of the law.

“If they’re sneaky, they can keep the confession,” he said.