Nel asked sports and exercise medicine professor at the University of Cape Town Wayne Derman if he was qualified to comment on the report by psychologists and three psychiatrists on the athlete's mental state.
"As far as it goes with the symptoms of anxiety... yes I can," Derman told the High Court in Pretoria.
Three psychiatrists and a psychologist had observed Pistorius for 30 days at Weskoppies Psychiatric Hospital following a court order.
Pistorius is charged with murdering his girlfriend Reeva Steenkamp. He claims he shot her by accident on February 14, 2013 through the locked door of the toilet in his Pretoria home, thinking she was an intruder about to emerge and attack him.
The State contends he killed her during an argument.
Nel said results from a psychometric test done on Pistorius showed that he scored 70, which was "normal and expected".
Derman said while the report stated that 70 indicated a high score, Pistorius did not meet criteria for clinical anxiety disorder.
Last week, Derman told the court that 70 was on the borderline and had the score been 71 the findings would have been different.
"Do you know, not even psychiatrists will comment on psychometry?" Nel asked.
"I do not know that," Derman replied.
He said he was entitled to comment on the tests done on the athlete.
"I was asked by Mr [Kenny] Oldwadge and I remarked that 70 is close to cut-off, because... here it is put out and explained what the cut-off means. So I am not working on any diagnosis."
Oldwadge is part of Pistorius's defence team.
Derman said he had spoken to the defence team's psychiatrist Dr Leon Fine before and after the observations.
Derman said they both agreed that 70 was borderline.
Nel argued that the State's psychiatrist Dr Carla Kotze would disagree.
"You don't know what 71 means."
Derman responded: "I presented research of my own in areas of anxiety. Those are issues to do with things that I work on every day... As a clinician with 20 years' experience I think 71 would have included something else."
Source : Sapa