The seven police officers accused of killing protester Andries Tatane are expected to apply for the charges to be dropped.
Two of the state's police witnesses claimed they were threatened into making statements to the Independent Police Investigative Directorate, the South African Broadcasting Corporation news reported.
Neither could identify any of the accused in a video of the protest because the officers were wearing helmets, according to the report.
State witness, officer Kabelo Pule, was discredited last year when he alleged the police had used excessive force when restraining Tatane.
It emerged that in an internal hearing he had claimed the opposite had happened.
Tatane was killed on April 13 2011, allegedly by police using rubber bullets, during a service delivery protest in Ficksburg.
Last year the case was postponed after the state cast doubt on its own witness, Captain Matshidiso Lesomola, an observer at the service delivery protest. – Sapa.