Two suspects appeared in the Johannesburg magistrate's court in connection with the killing of two police officers.
Their lawyers have tried -- and failed -- to force the state to hand over documents linked to the case.
The twin brothers stand accused of planning to blow up a US diplomatic mission and Jewish institutions in Johannesburg.
The Hawks also claim the two were prevented from flying to Syria, allegedly to join Islamic State.
The twins converted to Islam last year. Their family insists they are religious, but not violent.