SA sprinter and paralympian Oscar Pistorius sits in the dock during his murder trial at the high court in Pretoria on Thursday, 8 May 2014. The state claims Pistorius deliberately shot his girlfriend Reeva Steenkamp on 14 February last year but the athlete insists he mistook her for a dangerous intruder. Picture: Werner Beukes/SAPA/Pool

Johannesburg - The prosecution in the murder trial of Oscar Pistorius has continued its assault on the athlete's version that he and Reeva Steenkamp were asleep for hours prior to her death.

A defence medical expert speaking on Steenkamp's stomach contents - possibly indicating she had eaten shortly before her death - was grilled by the State for only being able to provide speculative evidence.

Professor Aina Christina Lundgren, a medical expert and anaesthetist, was brought to testify on gastric emptying.

Earlier in the trial, the State's own forensic experts deduced that the trace amounts of food in Reeva Steenkamp's stomach indicated she may have eaten about two hours prior to the shooting. This contradicts Pistorius's statement that he and Steenkamp were soundly asleep for hours before the incident.

Lundgren told the court that, as an anaesthetist, she had to be able to analyse the amount of food her patients had eaten prior to their surgeries. Food in the stomach can complicate surgical procedures.

She said that medical studies on how long a stomach takes to empty often vary, however, in normal individuals, up to 10 percent of a low-fat meal will remain in the stomach after four hours. Lundgren said this was generally accepted as fact.

Insoluble fibres like corn, broccoli and celery are indigestible and could remain in the stomach for longer, she added.

Lundgren said that in certain individuals, a stomach may not even empty after an eight-hour fast.

“It's not an exact science, unfortunately,” she said.

Pain, anxiety and sleeping could also delay gastric emptying, and pre-menopausal women may also have delays, according to the professor.

Psychological disorders such as anorexia or bulimia could also create delaying effects, as well as prescription “slimming” drugs and herbal medicines.

She had also analysed the report of the gastric contents of Steenkamp's stomach. She said certain fibres found in the stomach could have delayed the emptying, and Steenkamp's yoga exercises prior to sleeping could have done the same.

Lundgren did say, however, that one could only speculate on exactly when the model had eaten, and that it would be impossible to know with so many potential delaying factors.

Prosecutor Gerrie Nel said that Lundgren's evidence required some testing.

The professor said she had read the State pathologist's report. He said that Lundgren had just provided a list of possible delaying factors, but this was not based on anything found in the record. Nel said Lundgren did not know what medication Steenkamp was taking, and her testimony was almost entirely speculation.

Nel said that anaesthetists across the world generally agreed that six hours is generally enough to empty the stomach. But Lundgren said that in the interest of safety, sometimes longer periods were generally required.

Nel said that if Steenkamp had eaten about eight hours prior to the shooting, as Pistorius had claimed, by this point any normal person's stomach would have had to have been empty.

Lundgren said that if the couple had eaten a chicken stir-fry, the fibrous vegetables she'd eaten meant that no one could predict if her stomach would be empty.

“I don't think anyone could be that categorical, my lady,” she said.

Nel said that Lundgren never warned her patients against eating a stir-fry, but the professor replied she always recommended they only have a light meal.

He went on to say that according to the State pathologist even after death, enzymes would continue to digest food.

Nel said it was important to note that food was still detected in her stomach hours after the shooting, meaning Steenkamp's last meal was later than 7pm.

Lundgren admitted she did not feel she had the ability to criticise the forensic pathologist's conclusions.

Nel said that the fact that the accused was a professional athlete and his girlfriend was a model meant it was unlikely they would have consumed a high fat meal, which could have also delayed digestion.

Lundgren also added she had not consulted personally with Pistorius in writing her own report.

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The Star