CHARLESTON, S.C. — A jury signaled here on Friday that it was within a single vote of convicting a white former police officer in the fatal shooting of an unarmed black man.

But confusion reigned in the courtroom as the jury wavered about whether it was hopelessly deadlocked about the killing, which was recorded on video and became a symbol of the nation’s heated debate about race and policing.

Over the misgivings of a defense lawyer, Judge Clifton B. Newman, who presided over a four-week trial, did not declare a mistrial in the case of the former officer, Michael T. Slager, who shot and killed Walter L. Scott in North Charleston, S.C., on April 4, 2015. Jurors had been deliberating for about 48 hours and, by day’s end, had decided to resume their discussions on Monday.

Yet Friday’s proceedings, before a crowded courtroom that alternated between focused and flummoxed, were a remarkable display of the divisions in one of the country’s most closely watched cases. It has been seen as a bellwether for whether video evidence could lead to a rare conviction of a law enforcement officer in an on-duty killing.