For the first time, a New York appellate court has ruled that evidence once used to convict people in shaken-baby cases may no longer be scientifically valid. The ruling, which came in the case of René Bailey, a Greece woman convicted of causing the death of a child in 2001, has implications for a number of other people in state prisons for shaken-baby offenses. In this area alone, several dozen people have been convicted of murder or assault in such cases. The appeals court decision, released Thursday, changes the legal landscape in New York for alleged shaken baby cases, said Brian Shiffrin, a local appellate lawyer who was not involved in the case. “It makes it both easier for defense attorneys to argue the science and it puts the burden back on prosecutors to show there is evidence to support the theory of shaken baby syndrome,” said Shiffrin, who has handled appeals of shaken-baby convictions.