The murder trial of South African Paralympian Oscar Pistorius turned its focus on Tuesday to whether neighbours could have heard his model girlfriend screaming on the night he shot her dead.

   Prosecutors are trying to prove that Reeva Steenkamp screamed and that this showed the star athlete known as the "Blade Runner" knowingly gunned her down in a fit of anger after a row in the early hours of Valentine's Day last year.

   The defence claims Pistorius shot the 29-year-old model and law graduate four times through a locked toilet door after mistaking her for an intruder and that any screams came from him.

   State prosecutor Gerrie Nel attempted to show that tests conducted by engineer and acoustics expert Ivan Lin backed up the premeditated murder charge, arguing that neighbours who lived 177 metres (580 feet) from Pistorius could have been able to differentiate between a male and a female screaming.

   Lin said on Monday that at 177 metres away "it is very unlikely a listener can hear a scream let alone interpret the sound source reliably".

   But Nel insisted that Lin, a carefully spoken man in black-framed glasses, failed to do his sound estimates properly, saying he did not take into account factors that would have made it possible for the neighbours to clearly hear Steenkamp.

   "We have four people identifying the sound of a woman's voice, we have no exceptions," Nel said.

   "I do believe they heard a sound but I cannot say whether they were correct or incorrect. It's not for me to interpret that," said Lin.

   Nel asked Lin if he thought the state's witnesses were lying. "Not at all," he replied.

   The defence then called Pistorius's longtime manager Pete Van Zyl, who described Pistorius having a "heightened sense of awareness" and being fearful of crime but rarely aggressive.

   "I can recall only two specific instances where Pistorius lost his temper, I would not call it aggressive," said Van Zyl, a tan man with a grey buzz cut wearing a grey suit with a purple tie.

   Van Zyl also said Pistorius, who was at the height of his career following the 2012 London Olympic Games, wanted to involve Steenkamp in his life more than any other girlfriend.

   "I would describe it as a loving and caring relationship," said Van Zyl.

   The testimony appeared to strain Pistorius, who started wiping his face with his hands. (AFP)