The judge in the trial of South African athlete Oscar Pistorius is due to rule on a prosecution application for him to undergo a 30-day mental observation.
The request followed testimony from a psychiatrist who said that Mr Pistorius suffered from an anxiety disorder.
The BBC’s Andrew Harding in Pretoria says there is now the possibility of a lengthy delay in the case.
The double-amputee Paralympian denies intentionally shooting dead his girlfriend Reeva Steenkamp last year.
Mr Pistorius says he accidentally shot her through the toilet door in a state of panic, mistaking the 29-year-old model and law graduate for an intruder.
Psychiatrist Merryll Vorster told the court that the athlete had had an anxiety disorder since childhood and was “anxious” about violent crime.
His actions on Valentine’s Day last year “should be seen in context of his anxiety”, she said.
‘Danger to society’
If the prosecution request is granted, Mr Pistorius may spend up to 30 days in a state mental health institution for observation and assessment of his mental health.
The athlete has described the prosecution move as “a joke”, insisting that Monday’s evidence from Dr Vorster had “gone well”, our correspondent says.
But the prosecution argues that her testimony is further proof that the athlete is changing his defence – from putative self-defence, to an accidental shooting, to something now linked to his state of mind, he says.
The defence opposed the application before the court adjourned on Monday.
Our correspondent says that court sources have indicated that it is unlikely that Judge Thokozile Masipa will grant the prosecution its request.
Dr Vorster said that the reactions of Mr Pistorius in the early hours of 14 February 2013 would have been different to that of a “normal, able-bodied person without generalised anxiety disorder”.
She said that Mr Pistorius was more likely to respond to any threat with “fight” rather than “flight”.
But she said that this would not have affected his ability to distinguish between right and wrong and that it was up to the court to decide whether his anxiety disorder diminished his responsibility.
The anxiety disorder was the result of surgery at the age of 11 months to remove his lower legs, she said, a “traumatic assault” for an infant at that age.
She said that Mr Pistorius felt remorse over Ms Steenkamp’s death and had developed a depressive disorder as a result.
When state prosecutor Gerrie Nel asked Dr Vorster whether someone with anxiety disorder plus guns would be “a danger to society”, she replied: “Yes”.
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, Mr Pistorius – a national sporting hero dubbed the “blade runner” because of the prosthetic limbs he wears to race – could face life imprisonment.
If he is acquitted of murder, the court must consider an alternative charge of culpable homicide, for which he could receive about 15 years in prison.