A ballistics expert conceded on Monday that it would have been impossible to fire a shot from the front seat of the hijacked shuttle taxi that British businessman Shrien Dewani and his wife were travelling in.

Pieter Botha, for Dewani, put it to State witness Warrant Officer Pieter Engelbrecht that his testimony on ballistics was incorrect and that their own expert had concluded it was impossible.

"I do accept that it would have been difficult to fire the shot from the front if he [the shooter] was in a seated position," Engelbrecht said in the Western Cape High Court.

"It would have been impossible my lady."

Dewani is accused of the murder of his wife Anni during their honeymoon in Cape Town in November 2010. He has pleaded not guilty to the five counts against him, maintaining that the couple were the victims of a hijacking on November 13, 2010.

The State alleges that he conspired with others to stage the hijacking in return for R15,000.

Her slumped body was found in the abandoned shuttle taxi in Khayelitsha the following day.

Xolile Mngeni was convicted in 2012 of firing the fatal shot from the front passenger seat of the hijacked vehicle.

He died of a brain tumour on October 18.

Botha said their expert had used a similar vehicle and a model of a similar height and build as Anni.

He then adjusted the car seats to resemble those in the crime scene photographs and positioned the model in the rear seat by aligning the exit wound with the bullet defect in the original seat.

The defence expert then found that it would have been impossible for the shooter to reach the grip of the pistol had it been placed at Anni's chest in the rear seat.

"He even turned himself right around and placed himself on both knees and was still unable to reach the grip of the pistol. It was only when he wedged himself completely between the two front seats that he was able to reach the grip of the pistol," Botha said.

Engelbrecht accepted what Botha was telling him.

He also conceded that it would have been possible for the gun to go off accidentally if enough pressure was placed on the trigger.

The witness left the stand looking relieved.