Intro:

On Monday, the chief prosecutor in the murder trial of Oscar Pistorius, Gerrie Nel, challenged the credibility of a physician, Wayne Derman, who testified that the athlete has an anxious nature linked to his disability.

Script:

SOUNDBITE: (English) Gerrie Nel, prosecutor

"Remember we dealt with on Thursday with you being the treating physician and giving expert evidence on behalf on the accused. Can you remember that?

SOUNDBITE: (English) WAYNE DERMAN, professor of sport

"Yes my lady, I can. "

SOUNDBITE: (English) Gerrie Nel, prosecutor.

"You said that you don't think that there is conflict of interest to be able to do that."

SOUNDBITE: (English) WAYNE DERMAN, professor of sport

"My lady, I believe my report and my submission and my being here is as objective as I can be and I acknowledge I am his treating physician and wherever I can I have backed up my presentation with scientific evidence."

SOUNDBITE: (English) Gerrie Nel, prosecutor

" You are unable to be objective because you are a treating physician. So I am going to ask you a question based on that. If Mr Pistorius was a family member would you have had a problem in being objective expert?"

SOUNDBITE: (English) WAYNE DERMAN, professor of sport

"Yes sir, I would have."

SOUNDBITE: (English) Gerrie Nel, prosecutor

"Why would you draw a line between this person Mr Pistorius that you travelled the world with, spend lots of time with and a family member?"

SOUNDBITE: (English) WAYNE DERMAN, professor of sport

"My lady very simply because he is not a family member. He is one of a team of individuals that I travelled with. I believe that as a physician I Can be objective, I understand the issue that the prosecutor has and I believe I can be particularly with respect to my evidence that I have rendered in court."