Pistorius faces his day of reckoning in witness box

Oscar Pistorius will be watched closely throughout his testimony.

Tonight, Oscar Pistorius faces what could be the toughest challenge of his life as he testifies for the first time about the night he shot his girlfriend, Reeva Steenkamp.

It comes after a week's delay in the trial brought about by the illness of an assessor - an assistant judge - in the Pretoria court.

The first defence witness will be Jan Botha, a pathologist, rather than Pistorius, according to Brian Webber, one of the athlete's lawyers. Pistorius is likely to be the next to testify, marking the first time he speaks in public since the killing a year ago.

For legal experts, his first spoken account will be critical to the judge's decision. Pistorius will be tested not just against his two previous written versions of events, but also against a raft of direct and circumstantial evidence from witnesses called by the prosecution during its 15-day case.

"In this case, the criminal conduct, the act itself, is freely admitted," said Stephen Tucson, a criminal barrister and professor of law at Wits University in Johannesburg.

"The only issue for the court is his state of mind and the most direct evidence of that is his own testimony.

"If a ... suspect is lying through his teeth, the court can dismiss his version as untrue if it finds his state of mind as suggested by the circumstantial evidence contradicts him."

Pistorius, 27, will be watched closely throughout his testimony by Colonel Gerard Labuschagne, the head of the South African Police Service's investigative psychology section, who will look for weaknesses and mannerisms that could be exploited to the prosecution's advantage in cross-examination.

Gerrie Nel, the lead prosecuting counsel, has hitherto played second fiddle to Pistorius' barrister, Barry Roux, whose ability to tie witnesses in knots during cross-examination has made him a household name among the large proportion of South Africans transfixed by blanket coverage of the trial.

But the diminutive prosecutor is also known to be a skilled and dogged interrogator. Nel is expected to try to needle Pistorius into one of the angry displays heard about from other witnesses, the "snapping" that prompted Steenkamp to tell the athlete she was "scared of him sometimes".

He will also raise the inherent improbabilities many believe will decide the case against Pistorius: the fact that, despite knowing Steenkamp was in his bedroom, he assumed the noise from the toilet was an intruder rather than her; the fact that on deciding it was an intruder, he did not seek to speak to or warn his girlfriend.

Why, Nel will no doubt ask, did the athlete mention speaking to Steenkamp shortly before hearing a noise from the bathroom only in his second statement, and not his first? Why, too, did he not previously mention hearing the bathroom window slide open?

Among other issues likely to be raised are that he said the couple went to bed at 10pm, but the state pathologist said Steenkamp's stomach contents suggested she ate as late as 1am, and that he told the security guard who rang him after hearing shots: "Everything is fine."

He may be asked why Steenkamp took her cellphone into the toilet and locked the door, and why he did not hear a woman's screams like other witnesses.

- additional reporting AFP