A Gardiner man who killed and dismembered his father more than three years ago was confined to a the state psychiatric hospital Monday after he pleaded guilty to manslaughter, a prosecutor said.

Superior Court Justice Michaela Murphy found Leroy Smith III, 27, of Gardiner not criminally responsible in the death of his father, 56-year-old Leroy Smith II, in May 2014, Assistant Attorney General Donald Macomber, who prosecuted the case, said after the hearing.

Messages left with Pamela Ames, Smith’s Waterville attorney, were not immediately returned Monday.

Smith last week pleaded not guilty by reason of insanity to murder. A jury was ready to hear opening arguments Monday morning at the Capital Judicial Center in Augusta when Smith decided to change his plea. Smith was expected to take the stand Monday afternoon in his own defense.

“He suffered from schizoaffective disorder and a delusional disorder when he killed his father,” Macomber said. “He believed his father was going to kill him.

“It didn’t matter whether he was found guilty of manslaughter or murder, he was going to be confined to Riverview Psychiatric Center in Augusta,” he said.

In January 2016, Smith was the first person in Maine forced to be involuntarily medicated with antipsychotic drugs. Since that order was issued, Smith has voluntarily taken his medication, Macomber said.

The impact the medication has had on Smith’s mental health was obvious

Monday when Smith was in court, the prosecutor said.

“He seemed to have no mental health issues in court today, but if he’s ever going to get out of Riverview he had better continue taking his meds,” Macomber said.