Deputy First Assistant Prosecutor James Ronca agreed, saying reports were "very clear" that Rosa was unfit to proceed with a trial. The reports said her condition was progressive and irreversible.
Superior Court Terence R. Cook dismissed the murder charge, ruling that Rosa "lacks competency to stand trial."
With that, a case that had drawn national attention was closed.
Afterward, Ronca said that Rosa's disease was advanced and that the prosecution had "no legal basis to contest it, so we have to do the right thing."
Edwards said that in his 25 years as a lawyer, this was the first time that he had handled a homicide case that was dropped because a defendant was incompetent to stand trial.
"It may not be popular with some people, but it's appropriate," he said. "She was asking if her husband was in the courthouse."
Rosa's children rejoiced at the decision.
"I got my mother back . . . and we can put my father's death behind us," said Rosetta Rosa, 51, who moved in with her mother after she and her brother, Revello, learned of the shooting a few days after it happened.
Their mother said she shot him because she saw him sexually assaulting their granddaughter that night, said Rosetta Rosa, a former nursing home aide from Baltimore. The granddaughter, however, was not present at the time, Rosetta Rosa said.
Outside the courtroom, Rosetta Rosa looked at her mother fondly and repeated again and again, "It's over." Her mother repeated the words.
"It's beautiful," Revello Rosa said, referring to the ruling. "It's over, and everyone is happy. We get to take care of her" without any more worries, he said. He also moved back home - from Virginia - to be with his mother.
Fredricka Rosa had been free on $150,000 bail - with her family posting a required 10 percent - since the incident.
Now, her daughter said, the family members can move on with their lives.
Contact Jan Hefler at 856-779-3224 or firstname.lastname@example.org, or follow on Twitter @JanHefler. Read her blog, "Burlco Buzz," at www.philly.com/BurlcoBuzz.