Drayton Witt was convicted 10 years ago of murdering his 4-month-old infant son, Steven, by shaking him to death. His conviction was thrown out last spring after years of appeals that called into question the science behind it. This week, an Arizona judge dismissed the charges against Witt with prejudice. That means Witt will never go back to prison over Steven’s death: Prosecutors will not be permitted to retry him, as they’d said they planned to. Witt, who always insisted he did not hurt his son, has been fully vindicated in a case that helps mark a turning point for a certain kind of shaken-baby prosecution.