Oscar Pistorius's lawyers at his murder trial tried to roll back the prosecution's momentum at his murder trial, but the prosecutor sharply questioned a forensic expert for the defence.

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

Roger Dixon, a forensic geologist at the University of Pretoria and a 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.

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But Mr Dixon acknowledged he did not have ­expertise in some of the areas in which he was giving evidence, including sound, light and ballistics.

Mr Dixon offered a different version for the order of the shots that killed Ms Steenkamp to that previously described to the court.

Pistorius claims he mistakenly killed Ms Steenkamp while shooting at what he thought was an intruder.

Mr Dixon said it was his opinion that Ms 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.

The trial continues