Oscar Pistorius trial: Defence witness 'unqualified' to testify

Roger Dixon came 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)

Oscar Pistorius's defence was dealt a new blow after its forensic expert was hammered about his qualifications by state prosecutor Gerrie Nel on Wednesday.

Roger Dixon, a geologist at the University of Pretoria and a former policeman, was accused of being unqualified to testify as an expert witness as he challenged the state's murder case against the athlete.

In cross-examination, Mr Dixon admitted he did not have sufficient expertise in some areas in which he was testifying, including ballistics, blood spatter, sound and visibility tests.

Mr Dixon, who began testifying on Tuesday, challenged the state's ballistic expert, Captain Chris Mangena, who claimed Ms Steenkamp was first shot in the hip facing the toilet door, fell backwards and was struck in the arm and head as she tried to protect herself from the bullets.

At the time, he noted there could have been short break between the first and the second shot, giving her time to scream, which appears to back the state's case that Pistorius fired at the door, heard Ms Steenkamp fall down and deliberately changed position.

But today, Mr Dixon told the court the 29-year old law graduate was standing at an angle to the door with her "arm forward towards the handle", suggesting she was about the open the toilet door, when four shots struck her in quick succession, first in the hip and arm, as she was "falling and turning".

However, pushed by Mr Nel, known as the 'pit bull' for his aggressive tactics, about his expertise on the matter, Mr Dixon conceded he did not have qualifications in ballistics or pathology and is not affiliated to a forensic 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 told 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 forensic 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?"

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

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 on 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.