270 striking mine workers are being charged with murder after police shot dead 34 of their colleagues.
They are being tried under South Africa’s “common purpose” legislation because they were all in the crowd that confronted police two weeks ago at the Lonmin platinum mine in Marikana.
Families of the accused protested at the proceedings as they were led away in prison vans.
An official said police are not being charged because there will be a separate inquiry into their actions.
The strike at the world’s third biggest platinum producer was triggered by demands for a pay rise and recognition of a new trade union.
Police say they started shooting after being threatened by groups of miners armed with sticks and machetes.
It was the most deadly police response since the end of apartheid.
Ten people including two police officers and two security guards had been killed before the shootings.
Six of the 270 accused workers remain in hospital after being wounded in the incident.
The common purpose legislation was used by the former white minority regime to convict activists fighting against apartheid.