"Why did you not make sure that the person is the exact height as Mr Pistorius? Why?" he asked Dixon.

The height of a man shown in a photograph submitted by paralympian Oscar Pistorius's defence witness Roger Dixon is incorrect, the High Court in Pretoria heard on Thursday.

Dixon's photograph shows a man on his knees and 20cm shorter than Pistorius if he were on stumps.

Prosecutor Gerrie Nel asked Dixon why, as an expert, he did not make sure the height of the man in the photograph was correct.

"Why did you not make sure that the person is the exact height as Mr Pistorius? Why?" he asked Dixon.

Dixon said the photograph was taken "for demonstration purposes".

"I am not trying to mislead the court, My Lady... I am not suggesting that Mr Pistorius is the same height as the man on his knees in the photograph."

Dixon, a qualified geologist, took the photograph while standing across the street from Pistorius's house.

"The man's height is something I overlooked and omitted," he told the court.

Pistorius is charged with murdering his girlfriend Reeva Steenkamp on Valentine's Day last year.

Pistorius shot Steenkamp through a locked bathroom door at his home in Pretoria.

He says he mistook her for an intruder and that the shooting was an accident.

He is also charged with contravening the Firearms Control Act.

The State argues that he murdered Steenkamp following an argument.