(CNN) -- After five days of relentless cross-examination that left Oscar Pistorius quivering, sobbing and fumbling, the athlete's defense team now has a chance to discredit the prosecution by presenting its witnesses.
During cross-examination, prosecutor Gerrie Nel accused the athlete of inconsistencies and contradictions in his testimony.
His aim is to prove that Pistorius intentionally shot and killed his girlfriend, Reeva Steenkamp, after a heated argument in the early hours of Valentine's Day last year.
The defense team now gets its chance to cast doubt on that account and prove that the star sprinter shot his girlfriend through a closed bathroom door after mistaking her for an intruder.
Defense attorney Barry Roux called forensics expert Roger Dixon, who disputed a conclusion by a pathologist on the cause of Steenkamp's back wounds.
The pathologist said they were made by a bullet ricochet. Dixon said they were made by a magazine rack. The autopsy said they were made by a blunt, hard object.
Nel took every opportunity to discredit Dixon, including questioning his ballistics evidence when he said none of the bullets missed Steenkamp, while the state expert had said one did.
"You see how irresponsible it is to make inferences in areas where you're not an expert?" Nel told him.
At one point, Judge Thokozile Masipa ordered the state prosecutor to be less aggressive in his questioning.
Valentine's Day card
Pistorius has maintained he was terrified when he heard noises from the bathroom. When he entered the bathroom and heard a noise behind the closed toilet door, he pulled the trigger without thinking, believing an intruder was inside.
And in an apparent bid to show their romance was not as rocky as portrayed by the prosecution, Pistorius on Tuesday read a card that Steenkamp had planned to give him on Valentine's Day.
"Roses are red, violets are blue, I think today is a good day to tell you that I love you," the message read.
Last week, Pistorius, 27, took the stand for the first time since the trial started on March 3 to testify about what happened on the fateful day.
During his cross-examination, the prosecution released details of his relationship with the model and law school graduate, which began in November 2012. It included text messages retrieved from their phones.
Nel accused him of acting selfishly toward Steenkamp, picking on her and shunning a declaration of love that she sent via a phone message.
The court also heard audio recordings Dixon had made of a cricket bat striking a door similar to the one in Pistorius' toilet, and of gunshots fired through the door.
Prosecution witnesses have testified to hearing a woman scream, followed by gun shots, but the defense disputes their testimony, saying the only scream came from Pistorius after he had fired the fatal shots.
The trial was later adjourned for the day.
If Pistorius is found guilty of premeditated murder, he faces 25 years to life in prison.
The defense team will call 14 to 17 witnesses, Roux said when he opened his case. The trial is scheduled to continue until the middle of May.
Masipa will decide the verdict in collaboration with two experts called assessors. South Africa does not have jury trials.
The trial has gripped South Africa and sports fans worldwide who considered Pistorius a symbol of triumph over physical adversity.
His disabled lower legs were amputated when he was a baby, but he went on to achieve global fame as the "Blade Runner," winning numerous Paralympic gold medals on the steel blades fitted to his prostheses.
Only those in the courtroom saw Pistorius on the stand, because he chose not to testify on camera. His testimony could be heard in an audio feed.
The trial will be postponed until May 5 after Thursday's session per the state's request, the judge said.
CNN's Marie-Louise Gumuchian contributed to this report