Regional Magistrate Hein van Niekerk found the State could not prove its case beyond reasonable doubt.
Tatane died on April 13 2011, after police used rubber bullets and batons to subdue him during a service delivery protest in Ficksburg.
The case received huge media attention after footage of Tatane's alleged assault by police members was broadcast nationally.
Two of the state's police witnesses had claimed they were threatened into making statements to the Independent Police Investigative Directorate, the South African Broadcasting Corporation news reported last week.
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. – Sapa