Forensic investigator Roger Dixon is questioned by State prosecutor Gerrie Nel, not pictured, during the murder trial of Oscar Pistorius on Wednesday. Picture: Gianluigi Guercia

Pretoria - The State's onslaught on a defence expert witness in the Oscar Pistorius murder trial has been relentless, with the athlete having to wait two weeks before his defence can continue.

Roger Dixon returned to the stand in the High Court in Pretoria on Thursday morning for the remainder of his cross-examination, after Gerrie Nel on Wednesday questioned his credentials and integrity.

Dixon, a forensic geologist, was brought to the stand to testify on several forensic aspects of the case, including the bathroom door Pistorius shot through the night he killed Reeva Steenkamp.

Dixon and the defence's forensic team conducted a test on the toilet cubicle door by hitting it with a cricket bat and firing through it with a gun similar to the one Pistorius used.

Nel asked if Dixon was involved in the recording of these sounds of the bat and firearm, but the expert said he was not.

Throughout the State's case, neighbours of Pistorius claimed they heard gunshots coming from the athlete's home. The defence has argued that while some had heard the shots, others had confused the sound of the cricket bat breaking through the door with gunfire.

The prosecutor accused the defence of amplifying the sound sample of the cricket bat striking the door.

Dixon denied this.

The geologist was also questioned on how often he had visited the crime scene. Over the past year, Dixon said he'd gone to Pistorius's home at least seven times, most recently in April this year.

Dixon had visited the scene to determine the viewpoints of Pistorius's neighbours, the Stipps, as well as the lighting conditions in the athlete's bedroom. Pistorius has claimed his room was pitch-black on the night of the shooting, which is why he may not have seen Steenkamp going to the bathroom where he thought an intruder had broken in.

The expert said he had not used any equipment to measure light in the room, but that he had used his eyes.

Nel argued that what an individual can see in the dark was subjective.

“A measurement doesn't translate to me what I'm actually seeing,” said Dixon.

His analysis of the four bullets fired into the door was then questioned.

Dixon believed that all four bullets hit Steenkamp in some capacity, while the State argued that one had missed her entirely and ricocheted on the toilet wall.

But Dixon was unable to say where the magazine rack was in the cubicle on the night of the shooting. But he did deny the State's theory that she was propped up by the rack after being hit by the first bullet in the hip.

He said if she had been seated on the rack, her head would have been too high to receive the wound.

Nel argued that if Steenkamp was sitting on the floor, the second bullet, the highest bullet hole on the door, wouldn't have hit her in the head, as was suspected.

Dixon said it was most likely that the three bullets hit her as she was dropping to the floor after being shot in the hip.

Pistorius has claimed he fired four bullets in quick succession, but the State has argued there was a short pause between some of the shots.

Dixon could not say what angle Steenkamp's head would have been at as she fell to sustain the wound.

He said she may have hit the magazine rack, which was most likely against the wall directly opposite the toilet.

This would have caused the contusions on Steenkamp's back.

Nel asked how Dixon could believe this when the State's pathologist, Gert Saayman, had dissected the wound himself and determined this was not the case.

The court was shown a picture of the toilet bowl with bits of hair and tissue fragments.

Dixon said that her head must have eventually come to rest on the toilet bowl and the fragments could have also have been sprayed onto it if her head was shot in its vicinity.

Nel said this did not make sense, because if Steenkamp was sitting on the floor, as Dixon believed she was, her head would not have been high enough to spray the tissue on the bowl and lid.

Nel said it was odd that if Steenkamp had fallen and hit the magazine rack opposite the toilet with her back that she would suddenly fall forward to come rest on the toilet bowl.

But Dixon was willing to admit that because of blood marks from the rack's legs, it seemed as though it had been in one position and later moved.

Dixon had previously brought an image of a person standing on their knees to show the court what the Stipps could have seen on the night of the shooting.

Johan Stipp claimed he saw a man moving across the bathroom window.

The image showed that he most likely would have only seen the head of the person.

But on Thursday morning, Dixon explained the model in his photo was 20 centimetres shorter than Pistorius.

Nel asked why Dixon had not been forthcoming with this information, but the expert said the questioning had not allowed him to bring this up until Thursday.

The prosecutor also asked about why a model of Pistorius's height wasn't used for the shot.

“It was an oversight,” said Dixon.

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