Thank you. Moving on now to Oscar Pistorius. The paralympic athlete on trial for killing his girlfriend. An emotional day in the courtroom and ABC's hamish Macdonald has been there every day. He joins... See More
Thank you. Moving on now to Oscar Pistorius. The paralympic athlete on trial for killing his girlfriend. An emotional day in the courtroom and ABC's hamish Macdonald has been there every day. He joins us now from Pretoria, South Africa. Good morning, hamish. Reporter: Yeah, good morning, Lara. Right now we have this new witness in the stand. The defense says the timing of this has taken them by surprise. It's a professional boxer who says he helped to cover up the role of Oscar Pistorius in a separate shooting incident just weeks before the death of reeva steenkamp. Champion boxer Kevin lerena, a friend of Oscar Pistorius and reeva steenkamp is the fourth witness to take the stand in the olympic star's murder charge and alleged he fired a gun inside a restaurant just weeks before he killed reeva steenkamp on Valentine's day last year. A shot went off in the restaurant and then I was in shock. I looked down on the floor and exactly where my foot was stationary there was like a hole in the floor. Reporter: He's accused of firing the gun under their table and amid the chaos asking a friend to take the blame. The prosecution is painting a picture of a man careless with guns. I do remember Oscar saying, please, just say it was you. I don't want any attention around me. Just say it was you. Reporter: The Pistorius defense team is doing its best to create doubts about the testimony of another witness, Charlton Johnson, a neighbor who said he heard screaming and gunshots the night reeva steenkamp was killed. Mr. Johnson, I must stop you. You don't know what you're doing to yourself. Reporter: The defense argues Johnson communiqued his version with his wife Michele burger who also testified and that similarities in their testimony imply they discussed what they'd say in court. Once witnesses start to introduce it honestly then I wonder about it because right from the beginning it should have been honest. Reporter: Now, as damning as this testimony might be about another shooting incident, it could prove some of the charges against Oscar Pistorius, what we don't know, yet, is how this might prove he intended to murder his girlfriend, reeva steenkamp.
This transcript has been automatically generated and may not be 100% accurate.