Double amputee and Paralympain Oscar Pistorius appears in the North Gauteng High court in Pretoria, South Africa, Monday, 3 March 2014. Pistorius is accused of the murder of Reeva Steenkamp on February 14, 2013. He faces two charges; murder and contravention of the Firearms Control Act. Photo by Herman Verwey/Media24 - POOL

Pretoria - Dramatic testimony about a woman's terrified screams marked the first day of the murder trial of paralympian Oscar Pistorius on Monday.

A witness told the High Court in Pretoria four shots followed the woman's cries the night Pistorius's girlfriend was shot dead in his Pretoria home.

The testimony by Michelle Burger, an economics lecturer at the University of Pretoria, made for a gripping start to the paralympian's high-profile trial a year after the shooting.

Burger was the first witness called by prosecutor Gerrie Nel, and appeared to contradict Pistorius's denial of the State's claim that the couple had a row just before Steenkamp died.

Earlier, a sombre, soft-spoken Pistorius told Judge Thokozile Masipa “not guilty, My Lady”, when he was asked to plead to the murder charge and a range of other, lesser charges relating to alleged contraventions of the firearms act.

The State said since there were no eye witnesses to the event, it would therefore rely on circumstantial and forensic evidence to convict the 27-year-old athlete nicknamed “Blade Runner”.

“There were only two people in the house, there were no eye witnesses,” Nel said.

“The State's case is based on circumstantial evidence... and on what the neighbours heard...and lead ballistic and forensic evidence.

Pistorius, in a statement read out by his attorney, insisted that he had believed he was shooting at an intruder hiding behind his locked toilet door and said it was “unfair and incorrect” to say Steenkamp died after a domestic row.

But by calling Burger, Nel clearly set out to show the disabled athlete was lying.

Burger lives in the Silverstreams security estate, at a distance of 177 metres from Pistorius's home in the neighbouring Silver Woods complex.

Testifying in Afrikaans, she told the court she was woken up that night by the “blood-curdling screams” of a woman, followed by four gunshots.

Burger said she and her husband woke up just after 3am when they heard the noise, and her husband rushed to the balcony.

“She called for help. She screamed terribly and shouted for help. Then I heard a man also call for help. He called for help three times.”

Burger said she believed she was hearing the sounds of a robbery in progress and her husband called security guards and asked them to investigate.

“Then I heard her screams again,” said Burger. “It was like a climax. I heard her anxiety. She was very scared.”

Burger then heard shots, with a longer pause between the first and second shot than the rest.

“It was bang.....bang, bang, bang,” she said.

After the court's lunch break, Burger was aggressively cross-examined by Pistorius's advocate Barry Roux who tried to show that she was biased against his client and that her recollection was confused.

At one point, Roux put it to Burger that when Pistorius became anxious his voice rose to sound like that of a woman, and that at a distance of just under 200 metres she possibly could not hear the difference.

He also questioned why she did not hear Pistorius breaking down the locked door with a cricket bat after the shooting.

“You come from an attitude ... when you heard Mr Pistorius's version at the bail application you immediately decided it cannot be true.

“You decided if he said Reeva was not screaming, he was lying. In your view, he cannot be telling the truth.”

Burger insisted that she could not understand how she could unmistakably have heard the cries but Pistorius never heard it.

Roux retorted: “What you believed... was a woman screaming.”

Nel objected to Roux's line of questioning more than once, pleading for fairness to the witness.

The trial started 90 minutes late as justice officials had to locate an interpreter to allow Burger to give testimony in Afrikaans.

While the opening arguments of the State and the defence were broadcast live on television, her face was not shown as she had requested to testify off camera.

It remains unclear whether Pistorius will take the stand in what has been dubbed the trial of the decade.

Burger could be followed by more than 100 other State witnesses as the seasoned prosecutor sets out to do so in the glare of intense media scrutiny.

More than 300 reporters have vied for space in the court room and an overflow court and a scrum of local and foreign photographers have set up watch outside the court.