The prosecution has angrily accused Oscar Pistorius of tailoring evidence and overplaying his deep fear of crime to justify shooting dead his girlfriend, Reeva Steenkamp.

During a third day of stern cross-examination, prosecutor Gerrie Nel insisted on Friday that the 27-year-old was selective in his recollection of events.

Nel pushed the Paralympic champion on his version events in the seconds before he killed Steenkamp by firing four times through the stall door in his bathroom with his 9mm pistol on February 14, 2013.

“She was standing behind the toilet door talking to you when you shot her,” Nel put to Pistorius, saying the couple arguing was the only “reasonable explanation” for why she was standing behind the cubicle door and facing it.

“That’s not true,” Pistorius replied.

I don’t think anybody could say where she would have stood.

Pistorius says he shouted at what he thought was an intruder in his house and also at Steenkamp to call the police. Nel said that if that were the case, she would not have stood up against the door. She would have retreated away from it. And she would have responded to Pistorius, the chief prosecutor said.

“I don’t think anybody could say where she would have stood,” Pistorius replied.

The dramatic courtroom exchange on Friday ended the world-famous athlete’s first week testifying at his murder trial.

Amid volley after volley of questions about the minutiae of what happened that Valentine’s Day night and over apparent discrepancies in Pistorius’s accounts, the sprinter grew increasingly agitated.

“I’m not looking for an excuse, if I don’t remember it I don’t remember it!” Pistorius said, breaking down during one exchange about the placement of objects in his bedroom.

“This is the night I lost the person I most cared about, I don’t know how people don’t understand that,” he said through sobs.

Your version is so improbable that nobody would ever think it’s reasonably, possibly true it’s so impossible.

Earlier Nel had accused him of changing his version of events and of not remembering details that could be detrimental to the athlete’s case.

“Why are you changing your evidence?” Nel asked.

“I’m tired, my lady,” Pistorius said.

“I’m not convinced about your answer now, I think you’re trying to cover up for lies,” Nel said.

Nel also tried to show that Pistorius was not as concerned about crime as he claimed because he did not quickly fix a broken window and may not have turned on his house alarm the night the 29-year-old model was killed.

“Did you ever go into a police station and complain about anything?” asked Nel, after Pistorius listed the many times he had been a victim of crime.

“No, I did not,” Pistorius admitted, “except for the police stealing my watches, my lady,” he said referring to luxury watches that went missing at the Steenkamp death scene.

The athlete said he fired through his locked bathroom door thinking the model and aspiring actress was an intruder, as he had a heightened fear of being a victim of crime.

My presence unnerves him, I’m sure of it. He’s answerable to me.

Before starting a third day of pummelling cross-examination, Nel said Steenkamp’s mother acknowledged that Pistorius had requested for a meeting with the family.

Nel had attacked Pistorius for a public apology to the Steenkamps when he took the stand on Monday, but the double amputee sprinter said he had once asked to meet his girlfriend’s family in person, presumably to apologise.

June Steenkamp’s lawyer confirmed the request, Nel told the court.

“But they weren’t ready.

“Mrs Steenkamp felt it was important to be put on the record,” he said.

June Steenkamp has been hard on Pistorius and was quoted in a newspaper this week saying the athlete had gone from “hero to devil” after killing her daughter.

“My presence unnerves him, I’m sure of it. He’s answerable to me,” Steenkamp told Britain’s Daily Mirror.

Friday marked a difficult week on the stand for the accused, during which he has been accused of lying and fabricating evidence.

“Your version is so improbable that nobody would ever think it’s reasonably, possibly true it’s so impossible,” Nel thundered during the cross-examination.

“Your version … is a lie,” he insisted.

Is this one big conspiracy? They would do all this to you?

Confronted with crime scene pictures that showed his version to be improbable, Pistorius said police tampered with objects when they came to his upmarket house.

Someone moved fans, pulled the duvet on to the floor and opened the curtains, he said.

“Is this one big conspiracy?” asked Nel with incredulity. “They would do all this to you?”

Pistorius, known as the “Blade Runner” for his j-shaped prosthetic legs, has been charged with murdering Steenkamp in the early morning hours of February 14, 2013.

He faces a life sentence if convicted.

The double-amputee, once revered for his triumph over disability, has said he fired the shots accidentally and did not mean to kill anyone.

He also testified that he feared someone was coming through the toilet door and that his life was in danger.

This seemingly contradictory account was probed at length by Nel, who drew a concession from Pistorius that the shots should not have been fired at all.

Pistorius’s cross-examination is a key point in his trial and a stern test of both his version of events and of his resolve.