Defence advocate Barry Roux sits with his client, Oscar Pistorius, at the trial for the murder of his girlfriend Reeva Steenkamp. Picture: Siphiwe Sibeko

Pretoria - Oscar Pistorius's defence lawyer Barry Roux has set his murder trial alight with bruising questioning of State witnesses, but behind the bluster lie a few basic, long-used techniques of cross-examination.

No matter how irrelevant or esoteric, Roux is quick to pounce on any inconsistences in a witness's own testimony or compared to that of others. Whatever the specific issue, the aim is the same - to discredit the witness. “Did you hear three gunshots or two-or-three gunshots?”

Vagueness in testimony is equally seized upon in Roux's cross-examination. If a witness lacks an accurate recollection about one thing, perhaps they can't be sure of anything.

Roux has tried to lessen the impact of potentially damaging expert witnesses by proving they are a little less expert than might be assumed. Police forensics expert Gerhard Vermeulen has three decades of experience, but we now know he has never done a course on examining tool marks.

One key aim of cross-examination is to use State witnesses against the State. Roux has arguably had less success with this tactic than he has with discrediting witnesses, but his questioning led Vermeulen to admit Pistorius first shot through his bathroom door then hit it with a cricket bat - backing the sprinter's timeline of events.

Some witnesses appeared to show bias against Pistorius during cross-examination, which could jeopardise their testimony's validity. State witness Michelle Burger angrily questioned Pistorius's version of events when Roux probed her memory of hearing screams. He also insinuated forensic expert Vermeulen investigated evidence that only supported the state's argument.

Roux used interruptions or apparently unrelated requests to unsettle witnesses. He often used “No, my question is different” and “I am making a different point”, and once even asked for a witness's phone records. He goes further than he might in countries with jury trials, where such badgering would be counterproductive.

Roux's linguistic gymnastics often spun witnesses' testimony in his favour. “What do you remember today?” Roux asked one witness, implying they remembered differently before. He also made much of witnesses testifying in their second language and using words apparently in the wrong context. Roux was scathing after police forensic expert Vermeulen said he did not “bother” to probe a certain mark on the bathroom door. - AFP