The first witness in the Oscar Pistorius trial said that she heard "bloodcurdling screams" the night the Olympic sprinter shot and killed his girlfriend.

Michele Burger, who lives 194 yards away from the Pistorius house, awoke from her sleep last year's Valentine's day to hear a woman screaming. She then heard a man crying for help, followed by four gunshots.

Oscar Pistorius pleaded not guilty to the murder of model Reeva Steenkamp. The 27-year-old double amputee athlete has admitted to killing his girlfriend, but insists that he mistakenly thought she was an intruder when he fired four shots through a locked bathroom door.

"There was no argument," said Pistorius, responding to the accusation that he and his girlfriend had been fighting before the incident. "The allegation I wanted to shoot or kill Reeva could not be further from the truth."

However, his neighbor's testimony somewhat contradicts his version of events, as she describes Steenkamp as sounding terrified and in danger.

"She was very scared ... her shouts, her screams were petrifying," said witness Burger. "Before the gunshots, moments before the gunshots, I sat in the bed and it's the most helpless feeling I've ever had in my life. I anticipated something was going to happen, because of the climax of her shouts, I knew something terrible was happening in that house."

Defense attorney Barry Roux questioned if what Burger thought was a woman's screams could have been a frightened Pistorius and if the gunshots could have been a cricket bat breaking down the door. Burger was adamant that the "bangs" she heard were from a gun and the screams from a woman.

The murder case has been a major shock to fans of the famous Olympian, who had been described by Time magazine as "the definition of global inspiration" and listed among their 100 most influential people of 2012. Pistorius was born without lower legs, but still managed to compete in Olympic 400 metres semi-final using special prosthetic limbs, earning him the nickname "Blade Runner."

If convicted of premeditated murder, Pistorius may receive a mandatory life sentence with a minimum of 25 years.