Oscar Pistorius' "primal instincts" kicked in when he shot dead his girlfriend Reeva Steenkamp because he was in a vulnerable and fearful state, his defence lawyer said at the athlete's murder trial on Friday.
Double amputee Oscar Pistorius, 27, once a national icon for reaching the pinnacle of sport, is accused of murdering Steenkamp, a law graduate and model, at his home in Pretoria on Valentine's Day last year.
The defence says Oscar Pistorius, nicknamed the 'Blade Runner' after his carbon-fibre prosthetic running legs, shot Reeva Steenkamp through a locked toilet door in self-defence, believing she was an intruder, and that therefore he should be acquitted.
State prosecutor Gerrie Nel has spent the trial, which began in March, portraying Oscar Pistorius as a gun-obsessed hothead who deliberately shot Steenkamp, 29, four times through the door of the toilet, where she was taking refuge after an argument.
Defence lawyer Barry Roux said during his closing arguments that psychological evidence had proven the track star had a heightened fight response because of his disability.
"You're standing at that door. You're vulnerable. You're anxious. You're trained as an athlete to react. Take all those factors into account," Roux said, adding that Pistorius had felt exposed because he was standing on the stumps of his legs.
"He stands with his finger on the trigger, ready to fire when ready. In some instances a person will fire reflexively," he added. "That is your primal instinct."
Roux also argued that prosecutors had only called witnesses who supported their argument and not other key people, including police officers, who he said would have undermined their case.
On Thursday Nel said Pistorius had told "a snowball of lies" and had called on Judge Thokozile Masipa to convict the track star of intentional murder, a crime which could land him with a life sentence.
A potential lesser charge of culpable homicide - comparable to manslaughter - could carry a sentence of about 15 years.
Pistorius also faces three separate charges, including two counts of discharging firearms in public and possession of illegal ammunition, all of which he denies.
To arrive at a verdict, Masipa and her two assistants will have to weigh up the credibility of testimony on both sides, including that of Pistorius, who endured more than a week of torrid cross-examination during which he broke down repeatedly.
In the absence of a jury, experts say the crux of the case is whether Masipa accepts or rejects his version