AUBURN — A Turner man accused of fatally shooting his wife in 2010 is expected to argue Thursday that any statements he made to law enforcement officials around the time of his arrest should not be allowed at trial because he wasn’t properly advised of his constitutional rights.

Brian Nichols, 46, is scheduled for a 1 p.m. hearing on his motion in Androscoggin County Superior Court. He is expected to go to trial on a murder charge in May.

Nichols reportedly confessed to the killing, telling an Androscoggin County Sheriff’s deputy: “It’s over. I did it,” according to a police affidavit in court files. Asked where his wife was, Nichols said: “She’s in bed, dead. I shot her,” the affidavit said.

According to court records, Nichols told his nephew, Deputy Kevin Nichols, that he used a .30-30-caliber rifle and told the deputy where to find it. Brian Nichols said his wife, Jane Tetreault, 38, was having an affair with a man who was a client at the cleaning service where she worked and was a co-worker of hers at L.L. Bean. Police said they learned she had been afraid to go home because of Nichols’ accusations and had been sleeping at her office.

In January, Nichols changed his not guilty plea to not criminally responsible by reason of insanity.

At trial, prosecutors will have the burden of proving beyond a reasonable doubt that Nichols knowingly or intentionally killed Tetreault on May 8, 2010. By using an insanity defense, defense lawyer Donald Hornblower must show by a preponderance of evidence that his client couldn’t appreciate the wrongfulness of his actions.

Assistant Attorney General Lisa Marchese said Nichols had at least three psychological evaluations and was found competent to stand trial.

He’s been held without bail at the Androscoggin County Jail since his arrest.

A report at the Maine Office of the Chief Medical Examiner determined that Tetreault died from a gunshot wound to the head and neck.

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