Prosecutors in the Oscar Pistorius trial have sought to show that his girlfriend was awake and ate approximately two hours before her death, which would contradict the Paralympian’s version of events.

State prosecutor Gerrie Nel has argued that the Paralympic gold medallist shot Reeva Steenkamp in a fit of rage, in the early hours of Valentine’s Day last year.

Nel alleges that Pistorius and his girlfriend argued during the night and that Steenkamp took refuge in the toilet, where she was shot dead by Pistorius. He claims she ate after waking roughly around 1am.

But on Thursday, defence witness Aina Lundgren tried to cast doubt on the state’s claim, testifying under cross-examination that gastric emptying — the speed at which the stomach digests food — is an “inexact science”.

Prosecution witness Gert Saayman, a forensic pathologist, told the court earlier in the trial that the athlete’s girlfriend ate at about 1am, roughly two hours before her death.

But according to Lundgren, an anaesthesiologist, various factors – including the stage in the menstrual cycle and diet pills – can affect the speed of digestion.

Any attempt to determine when Steenkamp ate is “purely speculative,” she says, adding that the chicken stir fry dinner that Steenkamp ate contained “insoluble fibre” — vegetables — that may not have been digestible.

Nel questioned Lundgren’s claim, saying there was nothing about a chicken stir fry meal that would cause Steenkamp’s stomach to empty at a slower rate.

Pistorius says he was in bed asleep in his upmarket Pretoria home for five hours before he mistakenly shot 29-year-old Steenkamp through a locked toilet door, believing she was an intruder.

The 27-year-old Paralympic gold medallist shot the model and law graduate four times with a nine millimetre pistol in what prosecutors charge is premeditated murder following an argument.

Another defence witness, private ballistics expert Thomas Wolmarans, said it was hard to find the Winchester Ranger bullets Pistorius used to shoot Steenkamp, in order to carry out bullet trajectory tests, describing them as a “collector’s” item.

“This bullet, this one with the black tip is absolutely a collectors piece these days,” said Wolmarans.

“You can’t put your hands on it, I’ve tried all over.”

The defence is expected to conclude their case early next week, after the state has completed its cross-examination of their witnesses.