PRETORIA (AFP) - "Blade Runner" Oscar Pistorius arrived in court on Thursday to face judgment over the death of his glamorous lover, with the paralympian facing a possible life sentence if found guilty of murder.

Looking tense, the 27-year-old celebrity sprinter passed through a tunnel of cameras in front of Pretoria's High Court, for the climax of a six-month murder trial that has grabbed headlines worldwide and put the spotlight on the fallen hero's private life.

If found guilty of deliberately killing girlfriend Reeva Steenkamp on Valentine's Day 2013, he faces life behind bars, and notoriety that would eclipse his Olympic-sized sporting achievements.

Judge Thokozile Masipa's ruling on charges of murder and three firearms offences will likely be laid out over two days of careful legal argument.

A final verdict could come on Friday, but sentencing would take place weeks from now.

The high-drama, half-year trial has fed intense media interest worldwide, with live broadcasts veering into the realm of TV reality shows.

On Thursday, some 20 police officers were stationed around the courthouse, cordoning off the area. A man selling papers on a nearby street corner said he couldn't keep up with the demand: "Maybe you can come later," said Thomas Mdlule, the 29-year-old vendor, rushing to count out change for his customers.

Nearly 40 witnesses testified during the trial, including Pistorius himself, who broke down, weeping and at times vomiting as he heard how the 29-year-old blonde's head "exploded" like a watermelon under the impact of his hollow-point bullets.

Prosecutors described the double amputee as an egotistical liar obsessed with guns, fast cars and beautiful women, who refused to take responsibility for his actions. The court heard transcripts of phone messages in which the pair argued, with Steenkamp texting: "I'm scared of you sometimes, of how you snap at me."

Defence lawyers sought to explain there are "two Oscars": a world-class athlete and a highly vulnerable individual with a serious disability who acted out of fear, not anger, when he fired the fatal shots.

All the while his supportive sister and the implacable mother of the woman he killed looked on from the packed public gallery. June Steenkamp arrived to the courtroom early on Thursday, accepting a hug from a supporter wearing a "Imprison for Reeva" paper pinned to her shirt.

At its heart, the trial is simple. Pistorius killed the law graduate and model when he fired four shots through a locked toilet door in his upmarket Pretoria home. The sprinter doesn't deny this.

The question is why he did it. He says he thought he was shooting at an intruder and that Steenkamp was safely in bed. The prosecution says he killed her in a fit of rage after an argument.

The trial featured neighbours who testified to hearing female screams then gunshots - as well as defence experts who said this was impossible.

The verdict

Judge Masipa will begin proceedings by evaluating the evidence of each of the witnesses in turn, all the while careful to evoke strong case law and limit cause for appeal. She will then turn to her judgment.

Unlike the legendary live-television trial 20 years ago of US football hero OJ Simpson, who was controversially acquitted by a jury, Masipa is assisted only by two assessors.

She may decide that Pistorius is innocent, or that the state has not done enough to prove its case, resulting in an acquittal.

But if she decides Pistorius deliberately murdered Steenkamp, he could face a life sentence, which in South Africa means 25 years in jail.

Masipa could also decide that Pistorius did not kill her intentionally, but did act recklessly, opening the door to a lesser charge of culpable homicide, which could still carry a prison term.

Any guilty verdict is unlikely to be the end of the matter. There will be more courtroom arguments before a sentence is handed down and, most likely, an appeal to a higher court.

"The trial is the first leg of a multi-legged legal process. It's just the beginning," said lawyer David Dadic.

Whatever happens, Pistorius's glittering sporting career is likely to be over. Once a poster boy for disabled sport, he has been stripped of lucrative endorsement deals by global brands and has withdrawn from all competition.

For South Africans, the country's justice system is on trial as much as Pistorius. Many suspect that 20 years after apartheid, the system is still rigged in favour of whites, and an increasingly rich black elite.

"If Pistorius is not found guilty, it's a sad day for South Africa," said Khoza, a man passing by the court wearing a dark velvet blazer and pinstriped trousers.

"If he is not guilty on this, it's because he is a very powerful guy," said Khoza, "there will be no justice."