The Supreme Court has again reinstated the conviction of a California woman for shaking her 7-week-old grandson to death, a final ruling that ends a protracted dispute with the federal appeals court in San Francisco.

The justices voted 6-3 Monday to reverse the 9th U.S. Circuit Court of Appeals' ruling in favor of Shirley Ree Smith. The appeals court had three times set aside Smith's conviction, saying the case likely was "a miscarriage of justice." The appeals court said there was "no demonstrable support" for the prosecution's theory of the case.

But the high court said that even though doubts about Smith's guilt are "understandable," the appeals court should have deferred to state courts that upheld Smith's conviction.

Justices Stephen Breyer, Ruth Bader Ginsburg and Sonia Sotomayor dissented.

Ginsburg, writing for the dissenters, said the court should have passed up the chance to "teach the 9th Circuit a lesson" in a tragic case.

"What is now known about shaken baby syndrome casts grave doubt on the charge leveled against Smith; and uncontradicted evidence shows that she poses no danger whatever to her family or anyone else in society," Ginsburg said.