South African Olympic and Paralympic athlete Oscar Pistorius has been accused of trying to intimidate a friend of his former girlfriend Reeva Steenkamp.
The accusation came from the lawyer for Ms Steenkamp's friend.
Mr Pistorius is accused of shooting dead Ms Steenkamp, following a heated row in the early hours of Valentine's Day last year.
The athlete says he killed the 29-year-old after mistaking her for an intruder hiding in the toilet.
Lawyer Ian Levitt said: "During an adjournment in court today, my client Kim Myers was approached by Oscar Pistorius who whispered in a sinister undertone: 'How can you sleep at night?'.
"She is horrified by this disturbing act but will not be intimidated and intends to carry on attending the trial for Reeva."
Local media reports said Mr Pistorius denied speaking to Ms Myers when asked about the alleged incident at the court by reporters.
A reason for what Mr Levitt said was Mr Pistorius's attempt to intimidate Ms Myers was unclear.
She has regularly attended the trial and has been quoted in the media commenting on her close friendship with Ms Steenkamp.
The state prosecution has spent much of the 27-day trial trying to portray Mr Pistorius as an intimidating figure who bullied Ms Steenkamp.
However, the Paralympic gold medallist insists they were in a loving relationship.
Text messages sent between the couple were read out to the court earlier in the trial, one of which from Ms Steenkamp said she was scared of Mr Pistorius, although most of the retrieved conversations were loving.
The trial of Mr Pistorius, who faces life in prison if found guilty, has attracted huge interest across the world.
Before the shooting, Mr Pistorius was one of the most revered figures in sport, a man who had his lower legs amputated as a child.
He reached the semi-finals of the 400m at the London Olympics in 2012 running on carbon-fibre prosthetic "blades".