Oscar Pistorius in court for his ongoing murder trial in Pretoria. Pistorius is charged with the shooting death of his girlfriend Reeva Steenkamp on Valentine's Day in 2013. (AP Photo/Chris Collingridge, Pool)

Pretoria - Oscar Pistorius could spend the next few weeks at a psychiatric institution, after an expert witness suggested an anxiety disorder could have affected the athlete's behaviour on the night he shot and killed Reeva Steenkamp.

Specialist psychiatrist, Professor Merryl Vorster, was brought to the stand to give insight into Pistorius' mental state.

She said she had diagnosed him with an anxiety disorder, as well as secondary depression.

Earlier she mentioned that a person with such a disorder can react differently in highly stressed situations like the one Pistorius faced the night he shot and killed Reeva Steenkamp.

Vorster told the court she had not followed the trial intensely. Nel asked if media reports suggesting that Pistorius or his defence's experts were seen as poor witnesses would increase his anxiety. Vorster said she wasn't aware of these reports and could not comment. Prosecutor Gerrie Nel said Pistorius had testified he was under harrowing circumstances as he was “fighting for his life”. Vorster said she had first interviewed Pistorius on May 2, after he had already given testimony in the murder trial.

She then interviewed him 5 days later, after already speaking with his friends and family.

Nel asked what her job was on the defence's team.

“To bring psychiatric factors to the court's attention that may be relevant,” she responded.

She said that Pistorius' general anxiety disorder may be relevant to the court and its ruling.

Nel asked if a person with general anxiety disorder (GAD) who owned guns could be a “dangerous person”. Without blinking, Vorster said “yes”.

The prosecutor then asked if Pistorius' anxiety problem was similar to Post Traumatic Stress Disorder. She responded the disorders were related.

Because of this, Nel argued that Pistorius should - as according to the criminal procedures act - be taken to a psychiatric institution for observation to determine his mental state.

Defence advocate Barry Roux rebutted this by saying the Act read that only if a mental illness diminished the criminal responsibility of the accused that an observation be necessary. He said only if the accused was incapable of appreciating the wrongfulness of his act, should he be examined.

Nel argued it was not about “incapability”, simply that the accused's ability to realise the wrongfulness be “diminished”, which Pistorius' psychologist had implied with her analysis.

Roux said that only an observation would only be necessary if an allegation had been made that his disorder directly diminished this capacity.

But Nel said the defence had brought forward a psychologist to diagnose and link Pistorius' disorder to the night of the shooting.

The prosecutor asked Vorster if generalised anxiety disorder could impact on his ability to understand his responsibility in the shooting.

She said it did not, but that it could have affected his capacity to act.

It was then that Nel officially applied to the court to have Pistorius referred to a facility for observation.

Nel said that this witness implied a third defence for Pistorius, and this defence had to be interrogated.

He said that he would complete his application after finishing off Vorster's cross-examination.

Nel asked the psychiatrist any person, directly after killing his partner, even in anger, could immediately suffer remorse. She said it was possible. “Excluding psychopaths... That's what's expected?” asked Nel. Vorster agreed. Last week, a social worker testified that Pistorius' remorse was sincere, and implied she believed the shooting was an accident because of his guilt.

Nel then asked about whether Pistorius had said he felt sorry about killing Reeva Steenkamp.

She said he was remorseful over causing her death.

Vorster added that at no point had Pistorius mentioned any arguments or tension with Steenkamp, but had mentioned he thought an intruder was inside his bathroom on the night of the shooting.

Nel asked about Vorster's analysis that Pistorius would generally fight than flee from a situation.

He asked if a person suffering from GAD, with a tendency to be aggressive would make Pistorius an even more dangerous person. Vorster disagreed with this, as the fight or flight response was determined by Pistorius' anxiety, not two compounding factors.

She also said because of his disability, he often would not have the option to flee, especially if not wearing his prosthetics.

Nel asked if she had ever referred Pistorius to any other mental health professional. She said she had given him an option, but that she never conducted any official referrals when constructing her report for the court.

She also said that Pistorius had given her his own version of events on the night of the shooting.

Vorster was provisionally excused from the stand while the referral application was brought forward.

But Roux argued that his re-examination could make the application unnecessary if he clarified what the psychiatrist had testified.

He said the state was preventing the defence from contextualising the testimony.

Nel asked that he needed some time to prepare for the cross-examination, and court adjourned until Tuesday morning.

The Star