A 98-year-old woman is accused of strangling her 100-year-old nursing home room-mate after making the victim's life "a living hell" because she thought the woman was "taking over the room".
Laura Lundquist was sent to a Massachusetts mental hospital for a competency evaluation before her arraignment for second-degree murder.
Her defence lawyer, Carl Levin, said she had a "long-standing diagnosis of dementia, as well as issues of cognitive impairment".
She is believed to be the oldest murder defendant in state history, but might never go to trial because of her mental health issues.
Her roommate at the Brandon Woods nursing home in Dartmouth, Elizabeth Barrow, was found dead in her bed on September 24 with a plastic bag tied around her head.
Police initially speculated it was a suicide, but a medical examiner ruled it a homicide after an autopsy indicated strangulation.
Ms Barrow's son, Scott, had said Lundquist complained to nursing home officials about the number of visitors his mother received. He also has said Lundquist had made "threatening" and "harassing" remarks to her.
He declined to comment on the indictment, which was handed up yesterday by a Bristol grand jury.
Bristol District Attorney Sam Sutter said Lundquist suffered from paranoia and "harboured hostility towards the victim" and thought Ms Barrow "was taking over the room they shared".
He said Ms Barrow complained in the weeks before her death that Lundquist was making her life "a living hell".
The night before she was killed, she complained that Lundquist had placed a table at the foot of her bed to block her way to the bathroom.
Mr Sutter said Lundquist then punched a nurse's aide who removed the table, which was again found next to the bed at the time Ms Barrow's body was discovered.
Lundquist also told Ms Barrow she would soon get her bed by the window because she would outlive her, Mr Sutter said.
The two women had been roommates for about a year. Scott Barrow has said he asked nursing home chiefs to separate the women, but they assured him the two were getting along.
He said his mother told him she did not want to leave her room because that was where she and her husband had lived for several years before he died in 2007.
Mr Sutter said the case would probably never go to trial because of the possible incompetency finding and because the defence will likely involve mental health issues, which take a long time to prosecute.
Mr Levin said that if someone was found not competent to stand trial, the state would probably move for a civil commitment.
Prosecutors pursued second-degree murder charges because they did not believe Lundquist had the cognitive ability to form premeditation, which must be proved in a first-degree murder case, Mr Sutter said.
In a statement, the nursing home said the roommates acted like sisters, walked and ate lunch together daily and said: "Goodnight, I love you" to each other every night.
The home said Ms Barrow declined a room change in July and August.