State prosecutor Gerrie Nel opened his cross-examination on forensic geology expert Roger Dixon by first asking him about his qualifications.
Dixon said he was currently employed at the University of Pretoria's geology department in the lab and confirmed he was not affiliated to any forensic body.
Dixon is one of the experts from the defence team trying to prove that Oscar Pistorius is not guilty of murdering his girlfriend Reeva Steenkamp.
The athlete shot and killed Steenkamp on Valentine's Day last year and the state has charged him with premeditated murder.
He also faces two separate firearm-related charges and one of illegal possession of ammunition.
Nel shakes Dixon's credibility
Nel, whose main aim was to discredit Dixon, asked what the difference was between an expert witness and a lay witness.
The geologist explained that an expert has skills and knowledge in a specific field.
The state prosecutor asked, "You'll agree that you will have to show a court how you reached a conclusion?"
Dixon agreed and further explained that he obtained information from other expert witnesses, and reconstructed the logical sequence of events.
Dixon then began providing quite a long-winded explanation of how he reaches his conclusion.
Nel was seen leaning on his elbow during the elaborate explanation.
Nel asked, "Are you a sound expert?"
Dixon, who seemed a sarcastic, replied, "I hope that my evidence is sound."
Angrily, Nel asked again, "No sir! Are you an expert in decibels and sound?"
The expert evaded a simple yes or no answer and instead listed the people who were present at the sound test, which included a firing range manager, two ballistics experts, their wives and sound guys.
A clearly irritated Nel moved on and asked, "Your analysis of the dark, did that require any skills?"
Dixon said, "The instruments I used there were my eyes."
The prosecutor asked about the fibres off the door.
"Did you analyse them?"
He replied, "I looked at them under a microscope. I compared the fibres to photos of the socks while they were being worn by the accused."
Nel immediately asked whether or not Dixon was in possession of the socks or not.
Dixon tried evading the question with another lengthy explanation, but Nel immediately interrupted and asked the expert to strictly answer the question.
Dixon responded, "I didn't have possession of the socks. I made my deductions from seeing the fibres and a photo."
Nel then made it clear that he would quickly be moving through his questions to get answers and would then consult with "proper experts" on his answers.
It was also revealed by Dixon that he had not received any training in blood spatter analysis and had last taken a ballistics proficiency test in 2011/12, while other experts get tested at least once a year.
Nel also made Dixon concede that he did not match up the proper cricket bat to the marks on the door at the forensic labs in November last year.