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PRETORIA, South Africa -- A hollow-point bullet fired by Oscar Pistorius likely killed his girlfriend instantly, his murder trial heard on a day punctuated by the track star's vomiting and sobbing in the dock.

The 27-year-old double-amputee loudly retched repeatedly and threw up into a bucket as a pathologist gave graphic details of Reeva Steenkamp's autopsy and discussed injuries including a head wound.

Oscar Pistorius reaches for a bucket in the dock during his murder trial on Monday.SIPHIWE SIBEKO / Reuters

The model was shot with bullets designed to expand on impact and cause maximum damage, Prof. Gert Saayman said.

The expert's testimony was not broadcast or reported live on Twitter by journalists because of its explicit content under an order from Judge Thokozile Masipa.

Oscar Pistorius poses with his girlfriend Reeva Steenkamp in Johannesburg on January 26, 2013. Pistorius maintains he shot Steenkamp on Valentine's Day 2013 through his closed bathroom door by accident, thinking she was an intruder.Walso Swiegers / AFP - Getty Images, file

Saayman confirmed Steenkamp was hit in the head, arm and hip by three shots fired through the locked door of a toilet cubicle. A fourth round fired by Pistorius missed.

According to Saayman, the wound to Steenkamp's right hip likely would have been fatal. Her head injury was probably almost instantly fatal.

Steenkamp, a law graduate and personality on a television reality show, was wearing a pair of sports shorts with a Nike logo and a black undershirt when she was shot, he said.

In between bouts of sobbing and retching, Pistorius sat with his head bowed, covering his ears with his hands and a white handkerchief in an attempt to block out Saayman's testimony.

After court adjourned for the day, Pistorius sat for a few minutes with his hands over his ears and his body heaving and bent forward as his brother held a hand on his back.

Nicknamed "Blade Runner" for the special prosthetics he wears in competition, Pistorius admits that he shot Steenkamp on Feb. 14 last year. However, the Olympian argues that it was a tragic case of mistaken identity and that he thought the 29-year-old was an intruder who had broken in to his luxury home.

The trial continues.

Aliza Nadi and Jason Cumming of NBC News, Reuters and The Associated Press contributed to this report.