Oscar Pistorius mental condition claim is
Oscar Pistorius mental condition claim is "a fallback position," claimed prosecutor Gerrie NelGetty

Oscar Pistorius could be trying to beat the rap for killing Reeva Steenkamp by claiming he was mentally unstable at the time of the offence, the runner's murder trial has been told.

Chief prosecutor Gerrie Nel said that evidence from a psychiatrist who said Pistorius had a "anxiety disorder," was an effort by his defence team to undo the damage the fallen star had done to himself during his own testimony.

Dr Merryl Vorster told the trial that the defendant had generalised anxiety disorder (GAD) and was "hyper-vigilant" about security.

Nel said: "Can it not be seen as a fallback position? The timing of the witness being called and the timing of the consultants is important."

He claimed it was in the interests of justice for the court to find out more about Pistorius' mental condition and asked that the defendant be sent for observation. That could take up to a month.

Chief of the defence team, Barry Roux, said the request had "no merit" and the judge adjourned the trial to consider Nel's request.

Nel pointed out that Vorster was only called by the Paralympian and Olympian's defence team after days of gruelling testimony from the proseuction, during which time he contradicted himself and gave inconsistent evidence at times.

Under South African law, Pistorius cannot be found guilty of murder if it is shown he was in the grip of mental illness or 'intellectual disability".

Giving evidence at North Gauteng High Court, Vorster described the effect of GAD could have on Pistorius.

"It may impact on your capacity to live a normal lifestyle. By definition generalised anxiety disorder is a psychiatric disorder, so one can say it's a mental illness.

"But one has to look at the impact of that diagnosis on the individual's capacity to live and socialise."

The psychiatrist told Nel: "He [Pistorius] was still able to function at a high level and he still did socialise.

"He had distress because of his anxiety disorder but he was at that stage still able to continue with his life."

Pistorius denies premeditated murder and claims he mistook Steenkamp for an intruder inside his luxury home on the outskirts of Pretoria. The prosecution alleges he killed her following an argument between the couple.

Pistorius also faces charges of illegally firing a gun in public and of illegally possessing ammunition, both of which he denies.

The trial continues.