Pretoria — Prosecutor Gerrie Nel concluded his cross-examination of University of Cape Town professor Wayne Derman at the High Court in Pretoria on Monday.
He accused the sports and exercise medicine professor of bias.
He asked Derman if murder-accused paralympian Oscar Pistorius had heard someone moving inside the toilet in his Pretoria home before firing shots at the door on the night of February 14, 2013.
"No, there was no description of the magazine rack moving, just the sound."
Nel asked: "If he said he had heard movement inside the toilet, you would have remembered that?"
"I cannot recall," Derman replied.
When asked why he could not give a direct answer, Derman said his memory was not clear.
"My memory is very fuzzy on this... I am not certain."
He told the court Pistorius had not told him that he had heard movement inside the toilet.
"He never did."
Nel said Derman's use of the words "I cannot recall" showed his bias.
"You know he did not. Now you want to go back and use 'cannot recall'. If you on one instance, after I pressed you, were able to say no, why use recall?"
Nel said Derman would not give the court an answer that would not benefit Pistorius.
"You are not objective," he said.
Derman denied showing bias.
Pistorius is charged with murdering his girlfriend Reeva Steenkamp on Valentine's Day last year.
He shot her dear through the locked toilet door of his Pretoria home. He claims he thought she was an intruder about to emerge and attack him. She was hit in the hip, arm, and head.
The State contends he killed her during an argument.
Pistorius has also pleaded not guilty to three firearms-related charges.