Two very different versions of what happened in the moments before Oscar Pistorius' girlfriend Reeva Steenkamp died have already been heard in court.
The athlete stands trial on Monday accused of her murder in a case that will make South African history as the first to be broadcast live for millions around the world to follow.
He denies the charge, claiming he mistook Ms Steenkamp for a burglar when he shot her in the early hours of Valentine's Day, 2013.
The prosecution says Pistorius, 26, fired his gun four times into the door of a bathroom, knowing his girlfriend was inside after an argument.
Reeva Steenkamp was 'unarmed and defenceless', according to the prosecution
It is alleged she locked herself in the room after fleeing down a seven-metre passage from the bedroom at the runner's luxury home in Pretoria.
According to details outlined at previous hearings, the prosecution argues Pistorius followed her with his 9mm pistol, first putting on his prosthetic legs.
It is claimed he shot his gun four times through the door, killing an "unarmed and defenceless" woman, before the door was broken open from the outside.
The prosecution has rejected claims of mistaken identity - that Pistorius believed the person inside the bathroom was a burglar.
The defence, meanwhile, has alleged the defendant had "no intention" of killing Ms Steenkamp and was bereft at her death.
According to this version of events, Pistorius heard a noise in the early hours and thought an intruder had come through a bathroom window and was hiding there.
Defence lawyers claim he felt vulnerable and shouted for the intruder to get out and for Ms Steenkamp to call police.
It was dark and Pistorius thought Ms Steenkamp was lying on her bed, not that she was in the bathroom, lawyers have argued.
Pistorius speaks with his lawyer Kenny Oldwage at an earlier hearing
They claim Pistorius hobbled to the bathroom on his stumps and fired his gun - a 9mm pistol he kept under his bed because he had received death threats.
After the shooting, they said, he returned to his bed and saw Ms Steenkamp was not there.
It is alleged he shouted for help, broke open a door with a cricket bat and found she was alive before carrying her downstairs.
Pistorius wanted to protect Ms Steenkamp, not kill her, his lawyers claim.
Pistorius said he wanted to protect Ms Steenkamp, not kill her
The court battle will pit the wits of two of South Africa's leading lawyers and is expected to hear from 100 witnesses.
Pistorius has hired Kenny Oldwage, famous for helping acquit the man accused of killing Nelson Mandela's great-granddaughter Zenani in a drink-driving car crash.
He has also hired Barry Roux, known in court for his scarlet ties.
The trial will be one of South Africa's biggest ever legal showdowns, with Pistorius' team going up against veteran prosecutor Gerrie Nel.
Reeva Steenkamp's parents June and Barry. Pic: Channel 5
The judge will be Thokozile Matilda Masipa, a former crime reporter who became only the second black woman to be appointed to the high court in 1988.
The trial, which takes place in Pretoria, will have no jurors, since trial by jury was abolished in South Africa under apartheid in 1969.
Ms Steenkamp's mother, June, has indicated she will attend the trial.
However, her father, Barry, is expected to be at home, recovering from a near-fatal stroke, which his brother said happened while reading a newspaper report about the trial.
A layout of Pistorius' house in Pretoria, South Africa
Cameras will be able to "obtain a video and audio recording of the permitted portions" of the trial.
However, they will not be able to film the Olympic champion, defence witnesses or anyone else who objects to being on camera.
The mandatory sentence for someone convicted of premeditated murder in South Africa is life with a minimum of 25 years in prison.
:: Sky News will have live coverage of the trial from Monday, with a special highlights programme at 9.30pm.
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