HOULTON — The second phase of the trial for a man who was convicted last week of fatally stabbing a 10-year-old boy, the boy’s father and a family friend began Tuesday with testimony about the defendant’s mental state.

Jurors in Aroostook County Superior Court convicted Thayne Ormsby of three murder counts Friday. On Tuesday, the defense began its effort to convince them that Ormsby was not criminally responsible because of his state of mind.

Ormsby, 23, is using an insanity defense in the killings of Jeffrey Ryan, 55, Ryan’s son, Jesse, and a family friend, Jason Dehahn, 30, at Ryan’s home in Orient on June 22, 2010.

The defense contends that there’s more to the case.

On Tuesday, witnesses included Ormsby’s mother, who testified that she abused drugs and alcohol through much of his childhood, and an uncle, who said Ormsby stopped going to see his therapist.

Deputy Attorney General William Stokes told jurors Tuesday that it will be difficult for the defense to make a case of insanity because Ormsby admitted to police that he killed Dehahn and the younger Ryan to get rid of witnesses. He also fled to New Hampshire, where he was arrested July 2, 2010.

In Maine, murder carries a maximum penalty of life in prison.

Defendants who are deemed not criminally responsible for their actions are committed to a psychiatric hospital.