Court security officials were stationed inside and around the courthouse while a contingent of local and international media camped outside in the rain.
Tshwane metro police were preparing to cordon off streets leading to the court, with Palace Street the first to be closed.
A sniffer dog led into the courtroom earlier had left by 7.25am.
Police cars were stationed outside the court and a few metro police officers were milling around.
Motorists and passers-by gestured at journalists, stopping occasionally to observe what was unfolding.
A makeshift restaurant set up adjacent to the court became a haven for journalists, who got their coffee-intake at the crack of dawn.
Five step ladders had been set up at the court entrance by photographers wanting to get a better view during the day.
Pistorius, 27, is accused of murdering his girlfriend Reeva Steenkamp at his Pretoria home last year. He faces charges of premeditated murder and contravening the Firearms Control Act in a trial which is expected to last at least three weeks.
The proceedings in the wood-panelled courtroom will be broadcast live on television and radio, with the initial indictment listing 107 witnesses to testify for the State.