A neighbour of the South African Paralympic athlete has told in detail how she heard "blood-curdling screams" the night of Reeva Steenkamp's death.
Oscar Pistorius entered court today accused of the murder of his girlfriend Miss Steenkamp on February 13, 2013.
Appearing calm, the Paralympic gold medal winner pleaded not guilty to the charge before his neighbour Michelle Burger was called as the first witness.
Ms Burger told the court how she was woken at 3am to the sound of "terrible screams" before calling security.
She told the court: "(Reeva Steenkamp) screamed terribly and she yelled for help. Then I also heard a man screaming for help. Three times he yelled for help.
"Just after her screams, I heard four shots. It was very traumatic for me. You could hear that it was bloodcurdling screams."
Pistorius' lawyer Barry Roux inquired whether Ms Burger had mistaken the gunshots for the sound of Pistorius hitting the toilet door with a cricket bat after the shooting, suggesting she had still been asleep when the four lethal shots were fired.
Despite intense questions Ms Burger insisted that she was "100 percent sure" that she had heard gunshots.
Mr Roux continued to grill the witness over the screams she claims to have heard and asked why those details were missing in her original witness statement.
He asked: "Was there continuous screaming?"
She replied: "The screaming, it went very fast. I didn't expect that that evening."
Mr Roux said sharply: "What is it that you say to me by mentioning that?"
Ms Burger replied: "I didn't sit there with a stopwatch and take down the timing of each shot, or write when she shouted.
"What I can say is that there were four gunshots, and I heard her petrified screaming."
Mr Roux said: "You are not sure and what you are now doing is adapting, you're speculating, you're trying to close all the gaps."
Pistorius has always denied murdering Ms Steenkamp, insisting that he mistook her for an intruder, who had broken in via a bathroom window. He also denies that an argument had taken place between the pair the night of the shooting.
He stands accused of premeditated murder following a jealous row and then lying extensively about true events.
The double amputee faces charges of illegal possession of ammunition and two additional counts relating to shooting a gun in public in separate incidents alongside the murder charge.
If found guilty for premeditated murder, Pistorius faces up to 25 years in prison.