In the dock for the murder of his model girlfriend, Reeva Steenkamp, Pistorius appeared to change his defence under cross examination, casting doubt on his credibility.
The 27-year-old initially told the court that he shot Steenkamp through a locked toilet door, thinking the 29-year-old law graduate was an intruder coming to attack him in the dead of night.
But buckling under pressure, the double-amputee – who rose to international fame by being the first Paralympian to run against able-bodied athletes at the 2012 London Olympics – changed his testimony to say he fired the four shots accidentally.
His lawyers will spend at least the next two weeks trying to firm up his account.
Among the witnesses expected to give evidence this week is a psychologist who will speak to the athlete’s physical vulnerability, after details emerged in court of his obsession with guns.
Prosecutors have argued that the 2013 Valentine’s Day shooting came after a row between the couple that had been dating for around three months.
Pistorius fired four bullets through a lavatory door, killing Steenkamp who was in the toilet cubicle inside the athlete’s house in an upmarket housing complex in Pretoria.
State prosecutor Gerrie Nel has accused the athlete of “tailoring” his evidence, calling it “a lie”.
“Your version… is a lie,” said Nel, who has earned himself the moniker “bulldog” because of his aggressive style of questioning.
At times, the world famous sprinter, dubbed the “Blade Runner” wept and wretched in court, in a trial that is broadcast live on television.
His emotional outbursts, including loud wailing and sobbing had on several occasions forced the presiding judge, Thokozile Masipa to halt the proceedings to allow him to compose himself.