Authorities say both defendants tested positive for cocaine and morphine after the drag race, which was held on March 8 and led to the deaths of four children and left two others in hospital in a critical condition.
Protests by school-age youths have dogged the three-day trial since it began on Wednesday and police dispersed protesters using rubber bullets.
Some observers have accused the police responding to the protests in a heavy-handed fashion.
But Fiona Forde, a South Africa-based journalist, told Al Jazeera that similar protests and the police response were a near weekly occurrence.
"You must remember this within a broader context," she said.
"We're just months away now from the [football] World Cup and South Africa is desperate to make sure there is a very good image going out to the international community about this country and its safety.
"Anything like street protests is something you really want to keep a lid on."
Jub Jub, which means marshmallow, is one of South Africa's best know hip-hop artists.
His trial has been set for April 7.