Ahmed Timol was arrested in October 1971 and died five days later when he plummeted from the 10th-floor of the city's police headquarters.
Ahmed Timol, 29, was arrested in Johannesburg in October 1971 and died five days later when he plummeted from the 10th-floor of the city's police headquarters.
Officers said at the time he took his own life -- a verdict that was endorsed by an inquest in 1972 but finally overturned by a court earlier this month after a decades-long campaign by his family.
"An investigation has already started," Hangwani Mulaudzi, spokesman for the Hawks elite police unit, told AFP.
"The investigation will be finalised by the end of the year hopefully."
The judge who delivered the new ruling called for security branch officer Joao Rodrigues, who was accused of helping cover up the murder, to be prosecuted.
But he also acknowledged that the men who were directly responsible have since died.
The landmark case revived memories of apartheid police brutality and led to new calls for justice over dozens of activists who died in police detention under white-minority rule.