Oscar Pistorius guilty of premeditated murder and has lied, says prosecutor

State prosecutor Gerrie Nel dismisses athlete's testimony at close of trial for alleged murder of Reeva Steenkamp in 2013

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South African paralympic champion Oscar Pistorius
Oscar Pistorius attends the presentation of the final arguments during his murder trial at the high court in Pretoria. Photograph: Mujahid Safodien/AFP/Getty

Oscar Pistorius must be found guilty of the premeditated murder of his girlfriend Reeva Steenkamp, South African prosecutors have said, as the athlete's testimony at his trial was dismissed as mendacious and "devoid of truth".

Prosecutor Gerrie Nel, making his closing argument for the state, said the defence claim that Pistorius believed there was an intruder in his house on the night of 14 February 2013 would not help him escape conviction: "[If] I know there is a human being behind that door. I mean to kill that person and I do so," Nel said. "That it turned out to be Reeva is [legally] of no consequence."

Defence lawyers, Nel said, are set to argue that Pistorius acted in self-defence, faced with a perceived intruder, but also that he fired involuntarily because he was startled. "It's two defences that you can never reconcile," Nel told the judge, Thokozile Masipa, who will retire on Friday to consider her verdict. There is no jury.

At the high court in Pretoria, Nel repeatedly accused Pistorius of tailoring his evidence, saying that contested claims about the location of a duvet and two fans in the athlete's bedroom and inconsistencies in his version of events on the night were the consequence of a "snowball effect of lies".

"The court should have no difficulty in rejecting his full version of events, not only as not reasonably possibly true, but in essence as being absolutely devoid of any truth," Nel told the court.

"It's a snowball effect of lies. You tell one and it becomes too much. You just have to keep going and going."

The prosecution contends that – contrary to Pistorius's claim that the couple went to bed at 10pm – the pair were in fact awake and arguing.

A witness says she heard a row, and Steenkamp's stomach contents indicated that she was awake and eating at around 1am, Nel said.

Neighbours heard "intermingling" screams of a man and a woman before the four gunshots.

Barry Roux, for the defence, will make his main closing argument on Friday. But he took advantage of an extension to the court day on Thursday to point out what he called "mistakes" in the state's version.

He told the court that the original investigating officer, Hilton Botha, told "blatant lies" and argued that police had moved crucial evidence at the scene, saying that the defence would show the judge a photograph of one of the officers with his hand on a plug.

Friday's hearing is likely to focus on the timeline of events around the shooting, amid claims by Roux that the state's case "takes a nosedive" over the timing of the gunshots.

The state says the four shots were fired at 3.17am; the defence says this noise was the cricket bat breaking down the toilet door, and earlier sounds heard by neighbours were the shots.

The state has not provided an alternative explanation for the earlier noises, but its argument that neighbours heard female screams rests on the fatal shots being fired no earlier than 3.17am. The court has heard that Steenkamp would have been unable to cry out once she had been shot.

For the first time since the trial began in March, the fathers of Pistorius and Steenkamp were in the Pretoria courthouse. Pistorius is said to be estranged from his father, Henke, and Steenkamp's father, Barry, has been ill.

As well as the murder charge, Pistorius is also charged with having committed other offences – of discharging a firearm in a public place and illegal possession of ammunition. These alleged offences, argues the state, show a pattern of behaviour in which the athlete acts recklessly and does not take responsibility for his actions.

Pistorius denies all the charges laid against him.

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