NEW ORLEANS — A state grand jury has charged a now-91-year-old disgraced priest with sexually assaulting a teenage boy in 1975, an extraordinary prosecution that could shed new light on what Roman Catholic Church leaders knew about a child sex abuse crisis that persisted for decades and claimed hundreds of victims.

The priest, Lawrence Hecker, has been at the center of state and federal investigations of clergy sex abuse and a deepening scandal over why church leaders failed to report his admissions to law enforcement even as they permitted him to work around children until he quietly left the ministry in 2002. It wasn’t until 2018 that the Archdiocese of New Orleans publicly identified Hecker as a suspected predator when it released its list of “credibly accused” priests.