Carl Pistorius is on trial for the death of 36-year-old Marietjie Barnard, whose motorbike collided with his car on a road in Vanderbijlpark in 2008, Britain's The Mirror reported.
Motorcycle enthusiast Anton Coetzee testified that on the day of the accident Barnard was participating in an organized event called a "poker run" that involved visiting checkpoints to draw playing cards.
Under cross examination, Coetzee admitted that alcohol was available at the spots where bikers collected cards but said he didn't know if some of the participants were intoxicated.
Pistorius lawyer Kenny Oldwage told Coetzee that two state witnesses said there was a strong smell of alcohol on Barnard's breath.
"I didn't smell any alcohol on the breath of the deceased," Coetzee said.
Blood tests on Carl Pistorius conducted by police confirmed that he had not been under the influence of alcohol, the South African Broadcasting Corp. reported.