For days, the authorities watched warily as the crowd grew more militant. Two police officers were hacked to death, and eight other people were killed in violent clashes. On Aug. 16, the police were given the order to move in. The police said that they tried to chase away the miners with rubber bullets and stun grenades, but that they were forced to resort to live ammunition when the miners surged at them. The police said they retrieved six guns from the scene, including one that belonged to one of the dead police officers.

The bloodshed, so reminiscent of the horror of the apartheid-era police force’s firing on protesters, stunned the nation. The government, trade unions and the opposition roundly condemned the violence, and President Jacob Zuma set up an independent commission to investigate the killings and gave it broad powers to subpoena testimony.

The police involved in the shooting could still face criminal charges as well. The inquiry set up by Mr. Zuma has the power to refer cases for prosecution, and it is expected to deliver a report in five months.

Journalists at the scene caught some of the shooting on video and in photographs. The police account, meticulously laid out in a multimedia presentation the day after the clash, has been questioned by witnesses and journalists who have examined the scene and concluded that at least some of the workers were killed in what appeared to be much more suspicious circumstances.

Some of the dead and 78 wounded were struck far from the scene of the strike or shot in the back, according to local news reports, suggesting that they were not directly involved in the confrontation or were fleeing it.

The common purpose doctrine used by prosecutors against the miners has its roots in English law, and it is not unlike laws that allow anyone associated with a crime to be charged as an accomplice, Professor de Vos said. But based on the known facts in this case, bringing the charge makes little sense, he said.