CHARLESTON, S.C. — The trial of Michael T. Slager, the police officer whose videotaped killing of an unarmed black man staggered a nation already embroiled in a debate about police misconduct and racial bias in law enforcement, ended in a mistrial on Monday.

Judge Clifton B. Newman’s decision to halt the proceedings came three days after jurors signaled that they were within one vote of returning a guilty verdict against Mr. Slager, who could have been convicted of murder or voluntary manslaughter in the fatal shooting of Walter L. Scott. But on Monday, in a final note to Judge Newman, jurors said that “despite the best efforts of all members, we are unable to come to a unanimous decision.”

The outcome was disappointingly familiar to critics of police practices and conduct, and demonstrated the steep hurdles associated with prosecuting a police officer for a shooting while on duty. Although other cases involving claims of police misconduct have ended in mistrials and acquittals, few resonated as widely as this case in North Charleston, where Mr. Slager fired eight shots as Mr. Scott ran away.

“The fight isn’t over, that was Round 1,” said L. Chris Stewart, a lawyer for Mr. Scott’s family. “We all saw what he did. We all saw what happened.”