Oscar Pistorius trial: Reeva Steenkamp standing with 'hand on the door handle' when she was shot dead

Defence witness under intense scrutiny over his methodology and lack of qualifications

Forensic Expert Roger Dixon (L) answers to questions from State Prosecutor during the Oscar Pistorius trial at the North Gauteng High Court on April 16, 2014 (GETTY IMAGES)

Reeva Steenkamp was standing with her hand "on the door handle" before Oscar Pistorius shot her dead through a locked toilet door, his murder trial heard.

Continuing his evidence, forensic expert Roger Dixon told the court Ms Steenkamp was standing at an angle to the door with her "arm forward towards the handle" when he opened fire, suggesting she may have been in the process of opening the toilet door.

The athlete's defence team, led by Barry Roux, sought to cast doubt over the prosecution's claim that Ms Steenkamp "ran screaming" to the bathroom and locked herself inside the toilet hiding from Pistorius following a domestic dispute.

Returning to the witness box, Mr Dixon, a former policeman, challenged the state's version that Ms Steenkamp was facing the door when the first of three bullets struck her in the hip.

Today, Mr Dixon told Pretoria's High Court she was standing at an angle to the door when Pistorius fired four shots that struck her "like an instant amputation" in quick succession as she was "falling and turning".

His testimony appears to back the athlete's claim that he fired in rapid succession, and contradicts the state's claim that there was a short break between the first and second shot, where Pistorius deliberately changed aim.

The athlete, back in the dock after five days of cross-examination, kept his hands in his head as Mr Dixon described the impact of the Black Talon bullets that pierced his girlfriend's body.

On Tuesday, the forensic geologist told the court he carried out night-time visibility tests in Pistorius's house. He claimed his findings proved that his bedroom would have been almost pitch black on a "moonless" night like the night he shot and killed Ms Steenkamp.

However, when asked about his methods, Mr Dixon came under intense scrutiny from Mr Nel, telling the court "the only instrument" he used to carry out the test were his eyes.

The court also heard sound recordings of a cricket bat striking a door and gunshots fired through a door as the defence sought to prove the sounds are similar and could be confused.

"Your expertise [in the test] was wielding the cricket bat?" Nel asked Mr Dixon, to which the geologist replied: "My part of that test was to wield the cricket bat to produce the sound."

The sequence is crucial because several neighbours claimed they heard a woman screaming followed by loud noises at the start of the trial, which appears to back the prosecution's case that there was an argument before Pistorius fired at the door knowing Ms Steenkamp was inside.

His defence claims neighbours confused the sound of the cricket bat striking the door for gunshots and mistook the athlete's high-pitched voice calling for help for a woman screaming.

"Are you a sound expert, sir?" asked Mr Nel. "Have you received training in decibels and sound?"

Mr Dixon conceded he had not received specific training in sound analysis.

He also admitted the gunshot test had to be repeated because the firearm kept jamming, and noted they did not use the same ammunition as Pistorius because Black Talon bullets weren't available at the shooting range where the test was performed.

Asked about the qualifications of the music producer who recorded the test, Mr Dixon told the court he "had no idea" if he had experience in recording explosions. He also admitted he wasn't present when the second test was carried out.

In a series of tense exchanges, Mr Nel questioned his integrity and accused him of being "irresponsible" for giving evidence about the model's wounds without reading Ms Steenkamp's post-mortem in detail.

"You see how irresponsible it is to make inferences in areas where you’re not an expert. It’s irresponsible, am I right?," Nel told the court, addressing the witness.

Pistorius is accused of murdering girlfriend Reeva Steenkamp following a domestic dispute in the early hours of Valentine's Day last year. He claims he shot and killed his girlfriend in a case of mistaken identity, thinking she was an intruder.

The case continues.