PRETORIA, South Africa (AP) -- More than a year after he killed his girlfriend, Oscar Pistorius is expected to finally answer questions about why he shot Reeva Steenkamp through a toilet door when his murder trial resumes this week and his defense lawyers begin presenting the evidence they hope will save the Olympic athlete from going to prison for 25 years to life.
Pistorius' account that he killed Steenkamp by mistake is going to "stand or fall" with his testimony in court, a legal expert says.
Charged with premeditated murder for Steenkamp's death, Pistorius and his defense team say he will testify to counter accusations that he intentionally killed Steenkamp by firing four times through the door in his bathroom before dawn on Valentine's Day last year, hitting her in the head, arm and hip. Pistorius says he mistook Steenkamp for a dangerous intruder hiding in a toilet cubicle.
South Africa has no trial by jury, meaning Judge Thokozile Masipa will pronounce Pistorius guilty or not guilty of murder, and Pistorius has the chance to convince her that he did not intentionally kill the 29-year-old model.
But Pistorius' testimony also gives prosecutors the chance to cross-examine the celebrated double-amputee runner and scrutinize every aspect of his story.
Facing a possible life sentence, his questioning by chief prosecutor Gerrie Nel could be the biggest challenge yet for the 27-year-old Pistorius, a disabled athlete who fought for years to win the right to compete alongside able-bodied runners and made history by running at the 2012 Olympics.
Brian Webber, one of Pistorius' lawyers, said they had no choice but to put Pistorius on the stand. Legal experts say it's a risk Pistorius' defense has to take. In a rare comment after the prosecution closed its case, Pistorius said "we have a lot ahead of us."
Pistorius often reacted emotionally to details of Steenkamp's death in the four weeks of prosecution-led testimony at his trial. He retched loudly and vomited in court when a pathologist described Steenkamp's grisly injuries and cried and frequently covered his ears while sitting in the dock in an apparent attempt to block out graphic testimony.
During his own testimony, he will have to describe in depth his fatal shooting of Steenkamp.
"He can't ignore it," Marius du Toit, a criminal defense lawyer and former state prosecutor in South Africa who is observing the trial, said of Pistorius testifying. "He has to get into the box and confirm his version and be open to cross-examination. And this matter is going to stand or fall with that."
Defendants in South Africa have the right to remain silent but because he has admitted killing Steenkamp, Pistorius is under pressure to tell the court why he decided to shoot through the door with his 9 mm pistol without knowing -- in his version -- who was on the other side.
Prosecutors charge that Pistorius murdered Steenkamp after a fight and he must dispel their accusations that he intentionally shot her as she hid behind the locked door, legal experts say.
Pistorius likely won't be the first witness the defense calls on Monday, but he should take the stand straight after pathologist Prof. Jan Botha gives evidence.
Pistorius has not yet spoken publicly about the shooting, only giving his side in a written statement at his bail hearing a year ago and in court documents presented at the start of the trial last month. In those statements, Pistorius claims to have been in a loving relationship with Steenkamp but, in fear for his life, he shot at what he thought was an intruder after hearing a window being opened in his bathroom and then a noise inside the cubicle.
Even if he is acquitted of murder, Pistorius faces a negligent killing conviction which can carry a five-year prison sentence. His testimony must show that he acted reasonably when he shot four times from close range.
"A reasonable man most probably would not have fired four shots through the door," lawyer and observer du Toit said. "His actions were definitely not reasonable and I think that's his biggest problem."
Gerald Imray is on Twitter at www.twitter.com/GeraldImrayAP