Pistorius defense expert challenged

PRETORIA, South Africa -- The prosecution in Oscar Pistorius' murder trial on Thursday challenged the credibility of an expert witness for the defense, which was trying to show that the athlete shot his girlfriend by mistake.

Roger Dixon was called by the defense to give evidence to support Pistorius' story that he killed Reeva Steenkamp by accident, thinking she was an intruder behind a toilet stall door in his home.

Pistorius is charged with premeditated murder for shooting Steenkamp multiple times on Feb. 14, 2013. Prosecutors say he killed Steenkamp during an argument the two were having through the closed door.

The trial has been adjourned until May 5.

Continuing his cross-examination, prosecutor Gerrie Nel said Dixon, the third witness to be called by Pistorius' defense, had no expertise in some areas in which he was testifying and also had not been thorough in some of his examinations.

In one, the prosecutor criticized Dixon, a geologist, for not using Pistorius' exact height when the double-amputee runner is standing on his stumps.

"It is something I omitted. I overlooked it at the time," Dixon replied when questioned why his measurements were around 20 centimeters (8 inches) off in a test to see if Pistorius' head and body would have been high enough to be seen by neighbors through a bathroom window. He said he was not trying to "mislead" the court.

Dixon is a former policeman and an expert in the analysis of materials at crime scenes. His testimony touched on ballistics, gunshot wounds, pathology and blood spatter, and he also said he was involved in audio and visual tests. He conceded he is not an expert in any of those areas.

The bearded university researcher was subjected to tough questioning by Nel and has been ridiculed on social media and in the South African media for trying to be an expert in areas where he was not qualified.

Judge Thokozile Masipa will ultimately deliver a verdict. Pistorius faces 25 years to life in prison if convicted on the premeditated murder charge.