Samantha Taylor, who testified that she started dating Oscar Pistorius aged 17, also recounted an occasion when the Olympic sprinter fired a shot out of a car's sunroof.
Pistorius, 27, is accused of the premeditated killing of his girlfriend Reeva Steenkamp on Feb. 14, 2013. The double-amputee runner says he fatally shot her after mistaking her for an intruder.
Earlier, the 20-year-old Taylor also testified that she had split up with Pistorius after he cheated on her with model Steenkamp.
The trial continues.