Oscar Pistorius
Oscar PistoriusReuters

The state wants double amputee Paralympian Oscar Pistorius to undergo a psychiatrist evaluation, after a witness testified on Monday that Pistorius was diagnosed with mental disorder.

Pistorius, who is accused of killing his girlfriend Reeva Steenkamp last year, has claimed that he fired the shots that killed her believing she was an intruder. And on Monday, forensic psychiatrist Meryll Vorster told the court that Pistorius suffers from anxiety disorder and this would have influenced the way he reacted.

"It is my opinion, my lady, that Mr Pistorius has an anxiety disorder. If he was afraid that there was an intruder, then certainly having a generalised anxiety disorder would have affected the way he reacted to that fear," Vorster said, according to the Guardian.

Voster noted that Pistorius' amputation when he was just 11 months old, and his parents' pressure for him to act normal has had an impact on his mental well-being.

"He was never able to allow himself to be seen as disabled," she said. "He was always encouraged to be seen as being normal. Over time this could result in increasing levels of anxiety as the stress of appearing normal continued."

The divorce of his parents and the death of his mother when he was a teenager only led to Pistorius further developing and exhibiting symptoms of anxiety.

"The children were reared to see their external environment as threatening," she noted, adding: "Individuals with an anxiety disorder work hard to control their environment. In a way, his strict training regime and his diet helped him to alleviate his levels of anxiety."

Explaining why Pistorius took his gun when he allegedly went to check out the noise the night Steenkamp was killed, Vorster said she believed Pistorius' disability would force him to fight rather than flee if faced with a fight-or-flight situation.

If convicted of murder, Pistorius could be behind bars for 15 years or for life.

Interestingly, not many are buying into the defense trying to use Pistorius' disability as an excuse for his actions.

David Dadic, a litigation lawyer tweeted, "What I take from this is that even though he's disable, and had other stresses. He's not really too different to the rest of us."