AUBURN – A 20-year-old Lewiston man is challenging his sentence, saying he didn’t understand how long he would have to spend in prison in connection with a fatal stabbing two years ago.

Sergio Hairston was indicted on a murder charge, but pleaded guilty a year ago to manslaughter. In exchange, he was given a 20-year sentence, with all but 15 years suspended.

Hairston thought he would be released after about nine years if he stayed out of trouble. But administrators at the Department of Corrections told him he would have to stay behind bars closer to 12 years, with good behavior.

When Hairston learned that he would be locked up longer than he thought, he filed for a post-conviction review by the court. His attorney, Thomas Goodwin, also filed a motion to reduce Hairston’s sentence. That motion was heard in Androscoggin County Superior Court on Monday. Hairston appeared in a bright orange jail suit.

A judge signaled she would deny it because, in order to argue successfully for that motion, Hairston would have needed to show that an error occurred at the time of sentencing. The judge agreed with Assistant Attorney General Lisa Marchese that that hadn’t happened.

“The court was not operating under a misstatement of fact because there was no mistake about the plea agreement,” Marchese had written in a memo opposing the motion.

“The court gave no indication at all about what good time would be,” said Justice Joyce Wheeler.

In his motion for a post-conviction review on July 11, 2008, Hairston wrote that he had been “misinformed” about his plea and coerced into taking a manslaughter plea instead of going to trial on the murder charge.

He also was seeking a review of his plea because of “lawyer incompetency,” he wrote.

A judge who reviews requests for post-conviction reviews wrote that Hairston appeared to be claiming that he either entered an involuntary plea or had ineffective assistance of counsel at plea. “Both are proper grounds for review,” Justice William Anderson wrote.

A hearing is expected this spring to take testimony in Hairston’s post-conviction review. He and the two attorneys who represented him at the time of his plea likely would testify at that hearing.

Scott Quigley and Heather Walker, Hairston’s lawyers during his trial, were not available for comment Monday afternoon, according to their office staff.

Police said Hairston went to a Lewiston apartment on Bartlett Street to collect a drug debt from the son of the man Hairston stabbed to death.

Richard Lessard let Hairston into the second floor apartment then went in search of the phone number of his son, Dustin. Meanwhile, Lessard’s wife, Pauline, told Hairston to leave and whacked him with a box of window blinds. Hairston cut her with a knife, then stabbed Richard Lessard three times in the chest. He died from his wounds.

Police said they caught up to Hairston later on the street. He was carrying a bloody washcloth and knife. Blood on his hands and knife matched Lessard’s DNA.