AUGUSTA – Kenneth McDonald pleaded guilty Wednesday to murdering his mother, abruptly ending his three-day jury trial in Kennebec County Superior Court.

McDonald, 44, killed Janice McDonald, 80, on Aug. 24, 2009, in the home the two shared on Highland Terrace, Monmouth.

He pleaded guilty to intentional or knowing or depraved indifference murder, and Justice Michaela Murphy told him that murder carries a minimum sentence of 25 years in prison and a maximum sentence of life in prison.

The state’s deputy medical examiner testified on Monday that Janice McDonald died of sharp and blunt force trauma.

In the home’s bathroom, investigators found a steak knife coated with Janice McDonald’s blood and bearing bits of her hair. They also found the son’s bloodied clothing, scientists from the Maine State Crime Laboratory testified Tuesday.

McDonald earlier pleaded not guilty to the murder charge, but his attorney told the jury in his opening statement that McDonald killed his mother, but that the charge should be manslaughter, not murder.

The attorney, James Billings, said the stabbing was an act of rage, brought on by an argument after the mother refused her son permission to go to the coast.

Billings said the mother controlled every aspect of McDonald’s life, including whether he could take money from his savings account.

McDonald, who was characterized in court by family members and fellow workers as “slow,” was employed part-time at the Monmouth Transfer Station.

Neither he nor his mother drove, so they were dependent on relatives, friends and neighbors for rides.

On a recording played for jurors on Tuesday, McDonald said he and his mother got along well.  

He told Maine State Police detectives he liked to walk and to go to the library.

McDonald was missing from the home when his mother’s body was discovered, and he was arrested the next day on Bailey Island.