Oscar Pistorius' defence lawyer has grilled a police forensics expert for a second day, questioning his qualifications in a bid to discredit key evidence from the night the Paralympian shot dead his girlfriend.
Barry Roux resumed a searing cross-examination of Colonel Gerhard Vermeulen, hoping to rubbish his testimony suggesting the double-amputee sprinter lied about how events unfolded on February 14, 2013.
Pistorius, 27, stands accused of intentionally killing Reeva Steenkamp, 29, by shooting at her through a locked toilet door, though he says he mistook her for an intruder.
Pistorius' defence claims the athlete, after realising his mistake, tried to break open the door with a cricket bat, while the prosecution is positioning to argue that the couple were fighting and Pistorius fired the gun after failing to beat down the door.
Vermeulen on Wednesday testified that Pistorius was likely on his stumps when he bashed on the door with the cricket bat, contradicting the accused's account that he was wearing his prostheses at the time.
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The four bullet holes and cricket bat marks on the bathroom door offer valuable ballistic and forensic evidence about the sequence of events in the case.
Roux on Thursday attempted to show it was significant that Vermeulen did not have any formal qualifications to examine tool marks and did not conduct a microscopic examination of the door.
Vermeulen earlier admitted police may have mishandled the evidence, with footprints matching police boots appearing on the door in evidence photos, that were later rubbed off.
Roux claimed they could have been from Pistorius's prostheses, proving he had them on at the time the door was broken down.
He also said the door was removed from the crime scene and propped up against a cabinet and that shards of the door, which could have shone light on what happened the night of the killing, were missing.
"I did not pay attention to that stuff," Vermeulen said.
The admission could have far-reaching consequences for the prosecution's case.
"Roux's job is to create as much doubt as he can, and this was manna from heaven for him," said forensics expert David Klatzow.
"It was always unwise to take that door out and remove it from the scene," he said.
"The real question the court needs to address is this: was the relevant evidence destroyed or damaged to the extent that it has no value?"
If convicted of premeditated murder, Pistorius faces 25 years in jail.
