Local law enforcement has taken steps to improve relations with minority communities and increase training after a spate of deadly shootings between police officers and black men this past summer. But a mistrial last week in the case of a South Carolina patrolman charged with murdering an unarmed black man has left some in the African-American community wondering whether justice can be served in even the most egregious cases of misuse of deadly force. The video was unambiguous: A white police officer fatally shot an unarmed black man in the back as the man ran away.