RETORIA (AFP) - Olympian sprinter Oscar Pistorius comes face-to-face for the first time on Monday with the mother of the girlfriend he shot dead.

Pistorius, 27, looked nervous as he entered the North Gauteng High Court dressed in a black suit and tie, facing the prosect of a life sentence if found guilty.

The star athlete known as the "Blade Runner" is accused of murdering glamorous law graduate Reeva Steenkamp on Valentine's Day last year.

Inside the wood-clad court room, the victim's mother June, clad in black, looked on.

"I want to look at Oscar, really look him in the eyes, and see for myself the truth about what he did to Reeva," she told the British Daily Mail in an interview published on Sunday.

Further down on the wood-panelled bench, Pistorius's brother Carl, sister Aimee and a handful other relatives sat awaiting the beginning of proceedings, which are expected to take three weeks.

The families did not interact.

The prosecution argues that the double amputee knowingly killed Ms Steenkamp, while the defence will say he believed he was shooting an intruder.

Lawyers for both sides will lay out their opening arguments before Judge Thokozile Masipa in a case that has already been likened to the OJ Simpson murder trial in the US.

The state will seek to prove that Pistorius killed Ms Steenkamp in a rage after the couple quarrelled in the early hours of Feb 14, 2013.

Prosecutors are expected to rely on the testimony of neighbours who claim to have heard shouting from the house as well as phone records that might indicate strife between the two.

They are also expected to claim that Pistorius had watched porn just before the shooting, apparently contradicting his account of events.

The athlete, who became the first double amputee to compete against able-bodied athletes in the Olympics at the London 2012 Games, will also be asked why he allegedly told security guards at his luxury estate that everything was fine when they phoned after hearing gunshots.

In a bid to illustrate a history of reckless behaviour with firearms, the state claims that Pistorius on two occasions fired a pistol in public, once through the sunroof of a moving car and months later at a busy restaurant in Johannesburg.

He is also charged with possessing unlicensed ammunition.

Police investigators travelled to the United States to seek help from the FBI and computer giant Apple to access information on Pistorius's iPhone.

If the opening arguments finish early enough on Monday, the state may call the first of 107 witnesses, an exhaustive list that includes the defendant's former girlfriends, though it is unlikely everyone will be called to testify.

Born in 1986 in Johannesburg with no fibula bones, Pistorius had both legs amputated below the knee when he was 11 months old.

He used fibre-optic running blades in competition, earning him the nickname "Blade Runner".

If found guilty of premeditated murder, Pistorius faces 25 years in South Africa's notoriously brutal jails and an abrupt end to his glittering sporting career.

But the state has already admitted that ballistic tests suggest he might not have been wearing his prostheses when he fired the shots that killed Ms Steenkamp, which removes a key argument for premeditation.

During Pistorius's lengthy bail application last year, his defence team sketched the picture of a loving couple who even contemplated marriage.

CCTV footage emerged last week showing the pair kissing and flirting at an upmarket Pretoria grocery store 10 days before Ms Steenkamp's death.

The trial is slated to last three weeks, but will likely last longer as teams of lawyers weigh Pistorius's account of events against forensic and other evidence which the state says shows murderous intent.

A prosecutorial source said the trial would run until its completion with no planned postponements - unusual in South Africa's heavily backlogged judicial system.

South Africa's courts do not have juries, but Judge Masipa has appointed two senior advocates to help her in her decision.

In the courtroom, the front row of the public gallery has been set aside for the Pistorius and Steenkamp families.

Pistorius's family reiterated their support last weekend.

"We love Oscar, and believe in him, and will be standing by him throughout the coming trial," his uncle Arnold said in a statement.

Ms Steenkamp's mother June is attending on behalf of the family.

"Whatever the court decides at the end of his trial, I will be ready to forgive him," she said in her British Daily Mail interview.

Forty national and an equal number of international journalists have been accredited to cover the case from the courtroom.

A South African satellite network has set up a dedicated channel to cover the trial, parts of which will be broadcast live on television, while all of it will be available in audio.

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