PRETORIA, South Africa — Oscar Pistorius' defense tried to show Friday that his girlfriend was still falling as she was hit by the last of the shots that killed her and not sitting holding her arms over her head to protect herself, as prosecutors have argued.

A ballistics expert called by Pistorius' defense at his murder trial testified that Reeva Steenkamp was falling back in a toilet cubicle in the double-amputee athlete's home when she was hit in the head by the last of the four bullets Pistorius fired through the cubicle door.

"She was not sitting yet when the last shot was fired," expert Wollie Wolmarans testified.

Wolmarans' testimony contradicted evidence given by the prosecution's police ballistics expert who said Steenkamp was sitting on a magazine rack and desperately protecting her head with her arms when the last shot struck her.

Both sides say the first shot likely hit Steenkamp in the right hip as she was standing behind the door, causing her to fall.

The painstaking debate over detail reflects the defense's efforts to show that Steenkamp was not arguing with Pistorius after fleeing from him when she was shot in the pre-dawn hours of Feb. 14, 2013 — as the prosecution contends.

Pistorius, 27, is charged with premeditated murder for Steenkamp's shooting death. He says the killing was accidental because he mistook her for a dangerous intruder about to come out of the cubicle and attack him. The runner held his thumbs in his ears at times in the courtroom when Wolmarans talked about Steenkamp's fatal wounds.