PRETORIA: Oscar Pistorius’ lawyers at his murder trial on Wednesday tried to roll back the prosecution’s momentum, but the prosecutor sharply questioned the credentials and findings of a forensic expert for the defence.

Following the tough cross-examination of Pistorius that lasted five days, his defence attempted to re-assert his story that his killed his girlfriend by mistake, but the prosecutor strongly challenged the expert witness.

Roger Dixon, a forensic geologist at the University of Pretoria and former policeman, contradicted parts of the evidence given by a police ballistics expert and the state pathologist who examined the body of Reeva Steenkamp, fatally shot last year by Pistorius. But Dixon acknowledged that he did not have expertise in some of the areas in which he was testifying, including sound, light and ballistics.

Prosecutor Gerrie Nel was sometimes sarcastic while questioning Dixon, subjecting him to the same grueling scrutiny with which he challenged Pistorius, who often fumbled for answers in the witness box.

Dixon offered a different version for the order of the shots that killed Steenkamp in an attempt to back up Pistorius’ version of a mistaken shooting and rebuild his case after the Olympic athlete’s shaky testimony.

He said it was his opinion that Steenkamp was hit in the hip and the arm in quick succession by the first two of four shots while she was standing close to the door, and indicated he believed she may have had her right arm extended and maybe her hand on the door handle, as if she was about to open the door through which she was shot.

The defence was using Dixon’s testimony to try to cast doubt on the prosecution’s version that Steenkamp fled to the bathroom and was hiding in the toilet during a fight with Pistorius in the pre-dawn hours of Feb 14, 2013.

Nel has said that the double-amputee athlete shot Steenkamp through the door as she faced him and while they were arguing.

Dixon also said he took part in audio tests conducted by experts for the defence that showed the sounds of gunshots and of a cricket bat hitting a door were similar and could be confused.