His defence team earlier argued he was suffering from an anxiety disorder when he killed his girlfriend.
A report by experts will help the judge decide how significant this is.
The athlete denies deliberately killing Reeva Steenkamp. He says he shot her accidentally in a state of panic after mistaking her for an intruder.
BBC Africa correspondent Andrew Harding says the experts’ report seems unlikely to alter the course of this trial dramatically – the defence has already acknowledged that Mr Pistorius’s anxiety would not have stopped him knowing right from wrong.
The defence is expected to finish presenting its evidence in the next few days – calling perhaps three more witnesses.
Steenkamp, a 29-year-old model and law graduate, was shot through a toilet door at Oscar Pistorius’s house in Pretoria on Valentine’s Day last year.
The couple had been dating for three months.
The trial was adjourned on 20 May after Judge Thokozile Masipa ordered Mr Pistorius, 27, to undergo a month of tests as an outpatient at Weskoppies psychiatric hospital in Pretoria.
The prosecution requested the evaluation after a defence witness said the double amputee was suffering from Generalised Anxiety Disorder (Gad).
Mr Pistorius says he mistook Reeva Steenkamp – model and law graduate – for an intruder
Four appointed psychiatrists would “inquire into whether the accused by reason of mental illness or mental defect was at the time of the commission of the offence criminally responsible for the offence as charged,” Judge Masipa said.
The team would decide whether he was “capable of appreciating the wrongfulness of his act.”
It was revealed on Friday that one of the experts involved had suffered a heart attack, though this was not expected to delay the trial.
There are no juries at trials in South Africa, so the athlete’s fate will ultimately be decided by the judge, assisted by two assessors.
If found guilty of murder, Mr Pistorius, who went on trial on 3 March this year, could face life imprisonment. If he is acquitted of that charge, the court will consider an alternative charge of culpable homicide, for which he could receive about 15 years in prison.
Generalised Anxiety Disorder
The BBC’s Michelle Roberts explains what Generalised Anxiety Disorder is
Generalised Anxiety Disorder is a medically-recognised, long-term condition
People with Gad feel anxious on most days and worry about a wide range of issues
It is thought to affect around one in 25 people at some point in their lives and is more common in women than in men
Symptoms vary – making it tricky to diagnose
People with Gad may have difficulty concentrating, feel tired and irritable, feel sick, dizzy or sweaty and experience aches and pains
Gad tends to run in families, can follow stressful events, and may be linked to chemical imbalances in the brain
The main treatments include using talking therapies, relaxation techniques and medication. (BBC)