When the nursing home called to inform Mrs. Barrow’s son of her death, he had to press for details. “They said, ‘There was more to it,’ ” Mr. Barrow said.

For weeks Mr. Barrow knew nothing, until he came home from a sales trip to find his driveway filled with television news trucks. The Bristol County district attorney had just filed charges against the roommate.

That was not the way to seek justice for his mother’s death, Mr. Barrow said. “It’s like charging a 2-year-old who happened to take a gun off a table and shoot a sibling,” he said.

Ms. Lundquist’s lawyer, Carl S. Levin, said, “We maintain her innocence.”

Having been blocked from court, Mr. Barrow was forced to go to arbitration. The nursing home had to turn over files that included the details about Ms. Lundquist’s past behavior.

Mr. Barrow said he was optimistic but soon became disillusioned with the process. His legal team said they discovered that the arbitration firm running the hearing had previously handled more than 400 arbitrations for the law firm representing the nursing home company.

His lawyers David Hoey and Krzysztof Sobczak questioned whether the process could be objective when the arbitration firm had drawn so much business from one of the parties. The arbitrator ultimately ruled in the nursing home’s favor but provided no explanation. His ruling consisted of a single check mark, indicating that Brandon Woods had not been negligent in its care of Mrs. Barrow.

But Mr. Barrow kept fighting. For him, the case has always been about the nursing home, not about Ms. Lundquist, who is now 104 and remains in a state hospital in Massachusetts. She is evaluated yearly to determine if she can stand trial, but given her age, that seems unlikely, a spokesman for the district attorney said.

“I can’t do anything for my mother,” Mr. Barrow said, “but I want people to realize that they have to investigate nursing homes. Everyone could end up there.”