Olympic and Paralympic track star Oscar Pistorius sits in the dock during court proceedings at the North Gauteng High Court. Pistorius is on trial for murdering his girlfriend Reeva Steenkamp at his Pretoria home on Valentine's Day last year. REUTERS/ Werner Beukes/Pool

Johannesburg - Oscar Pistorius' claims that he was standing on his prosthetic legs when breaking down his bathroom door on the night he killed Reeva Steenkamp have been strongly opposed by an expert witness. But the defence has put forward a strong argument that some of the witness' evidence analysis could have been contaminated.

Colonel Johannes Vermeulen testified that through analysis of the marks on the door that Pistorius tried to break down with a cricket bat had proven the athlete was on his stumps.

Vermeulen told the court that for Pistorius to have been on his prosthetic legs, he would have had to have been in “an unnatural position” to have created the two large indentations on the door.

The defence had tried its utmost to argue against this analysis.

Defence advocate, Barry Roux made Vermeulen demonstrate on his knees that if he lifted his feet, as though he had no legs, he would lose balance and could not have been able to break down the door.

Vermeulen said he had lost balance, but wasn't willing to testify on Pistorius' balance as an expert.

However, he did argue that someone who was born without legs, he would have greater balance. He then said that if Pistorius could have maintained balance while shooting a firearm - as the defence has claimed - he probably could have been stable while using the cricket bat.

The lawyer then asked about the possibility that additional marks on the door could have been created by investigators after the incident, but Vermeulen was unable to say he'd seen images of the door on the day of the incident.

Roux then asked about some missing pieces of the door, which Vermeulen admitted he had not asked about, even though it could have “shed more light” on his findings.

Roux asked why such flaws in the investigation and the understanding Pistorius was not on his prosthesis were not compiled in a second report. Vermeulen argued these issues were presented by prosecutor, Gerrie Nel, to the defence.

This afternoon, Roux queried what had come first, the bullets or the cricket bat.

Vermeulen testified that the way in which a crack ran through the door and a bullet hole indicated at least one of the shots was fired first.

Roux then returned to the missing pieces of wood that had come out of the door.

The lawyer presented an image of investigators, including Vermeulen working on the door, and pieces of wood clearly visible next to it.

But Vermeulen said he didn't notice the splinters during his investigation.

Roux then referred to a mark on the door that he said had been created by Pistorius' prosthesis, and that fabric from his sock could be found embedded inside it.

The lawyer continued to suggest that Vermeulen had missed crucial evidence including this particular mark.

Vermeulen was only able to say it wasn't caused by the cricket bat.

He said there was no evidence that Pistorius had kicked down the door except for Pistorius' version of events. But Roux questioned why the door had not tested to determine if it had been kicked, and Vermeulen explained that this had not been requested as part of the analysis.

The defence then pointed out that Pistorius had said he'd tried to kick down the door, and that it was odd the state chose not to test this claim.

Roux then handed over a picture of a shoe print on the panels of the door that were on the floor.

Vermeulen said it was likely the footprint came from police issue shoes, and detectives may have stepped on the evidence - thereby contaminating the scene.

He said the door was brought to him weeks after the incident in a body bag, the panels separate from the frame. Roux implied that the footprints had been wiped off the door before it had been given to Vermeulen.

Vermeulen admitted the door and bat were not in the same condition when they arrived as they were on the day of the shooting.

He said he didn't know how many people had handled the door before he did, or where and how it was kept.

However, he did say the door was reassembled and held in place with Prestik and screws.

The court was shown the panel that had fallen from the door during the incident, surrounded by a pool of blood.

When the photo was shown, Pistorius covered his face with his left hand.

Vermeulen admitted there was one mark that was not on the door on March last year that is visible now.

Vermuelen said the exhibits were meant to be kept under lock and key with controlled access.

He conceded that “something” must have happened to the door after he first received it on 8 March 2013.

Roux insisted that Vermeulen bring proof of previous analyses he had performed specifically on doors.

Vermeulen also admitted to the court he is not a certified tool mark examiner, even though there are others in his department.

The trial continues on Thursday.

The Star