A South Carolina jury hasn’t been able to decide whether to convict a white former police officer in the shooting death of a black man — so the judge has declared a mistrial. Former patrolman Michael Slager was charged with murder in the shooting of Walter Scott, but jurors were also allowed to consider a lesser charge of voluntary manslaughter. Cellphone video showing Scott being repeatedly shot in the back from a distance inflamed the national debate about how blacks are treated by police.