Under pummelling cross-examination, Oscar Pistorius admitted on Thursday that he had "no reason" to fire the shots that killed Reeva Steenkamp, as prosecutors began to zero in on apparent inconsistencies in key parts of his account.
During the second day of gruelling questioning, prosecutor Gerrie Nel began to pick at Pistorius's explanation of why he fired four times through his toilet door on Valentine's Day 2013.
Pistorius has been charged with murdering his 29-year-old model girlfriend and faces a life sentence if convicted.
The Olympian has said he fired the shots accidentally and did not mean to kill anyone. He 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.
"We know for a fact there were no intruders in your house that night, we know for a fact there was no ladder against the wall," Nel said. "We know for a fact that you had no reason to shoot, objectively speaking."
Pistorius responded: "That's correct my lady."
Regardless of who Pistorius believed was behind the door, he could face a stiff sentence if judge Thokozile Masipa believes he purposely used lethal force without reasonable cause.
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.
During the five-week trial the world-famous athlete has appeared fragile, frequently crying in court and becoming physically sick when the gruesome details of Steenkamp's injuries were discussed.
'All about I'
Nel spent most the first part of his cross-examination accusing Pistorius of being a selfish, controlling boyfriend and caring more about himself than the death of his girlfriend.
Nel tore into the 27-year-old's account of his relationship with Steenkamp.
"It's all about 'I'. It's all about Mr Pistorius," Nel said, reading cell phone messages in which Steenkamp said she was upset and "scared" of Pistorius's behaviour.
"She's scared of the feelings that she has for me and the way that I brushed her off," the athlete explained the message his girlfriend sent over social messenger WhatsApp.
Nel also accused Pistorius of making a public apology to Steenkamp's parents just to make himself feel better.
"Did you feel better after the apology?" Nel asked facetiously.
Steenkamp's mother June has said she wanted the Paralympian to see what he did to her daughter.
"He must see me there in the court, he must feel my eyes boring into him, I think it makes a lot of difference," she told Britain's Daily Mirror newspaper. "I look at Oscar the whole time, to see how he is coping, how he is behaving. I'm obsessed with looking at him, it's just instinctive, I can't explain it."
After sitting in court stoically, Steenkamp said she breaks down at the end of the day.
"I keep it all in and when I get back to the hotel it all comes out and I break down."
Nel also used questions about three gun charges to try and show that Pistorius was irresponsible.
Pistorius has denied firing a gun in public on two separate occasions, and the possession of unlicensed ammunition.
"I didn't pull the trigger. I didn't have time to think," he said about firing a gun in a Johannesburg restaurant in 2012.
"'I'm a gun enthusiast, I didn't have time to think,'" Nel mimicked him sarcastically.
He also said his legal team had told him it was legal to keep his father's ammunition in his home safe.
"It's now the third occasion that you blame your legal team when you don't want to take responsibility!" said an exasperated Nel.
Pistorius earlier blamed his lawyers for discrepancies between his accounts given in written statements and his later verbal testimony.
Defence lawyer Barry Roux is expected to call up to 17 more witnesses in the remainder of the case, to testify on ballistics, whether Steenkamp urinated, damage to the toilet door, sound, as well as Pistorius's fear of crime and "vulnerability" on his stumps.
Originally scheduled to run for three weeks, the case has been extended until mid-May but could go on even longer.