In a case that has transfixed the nation and become an endless source of gossip, prosecutors claim Jessica Kumala Wongso spiked the Vietnamese iced coffee of her friend Wayan Mirna Salihin at an upmarket Jakarta shopping mall in January.

However, Victorian forensic pathologist Dr Richard Byron Collins said a report by an Indonesian toxicologist found no cyanide in Ms Salihin's gastric fluid 70 minutes after her death.

Tests for cyanide in her bile, liver and urine also came back negative.

A small amount of cyanide was found in Ms Salihin's stomach several days later after her body had been embalmed.

But Dr Collins, who told the Central Jakarta District Court he had performed 11,000 post mortems, said there were a number of factors that could explain this "very low" level of cyanide in her stomach.

"If you take the toxicology results as they are and the explanation that the very low level of the gastric content was due to postmortem changes then it is impossible in my view to conclude that the death was due to cyanide poisoning," he said.

Dr Collins was critical that only an incomplete autopsy had been carried out, which he said failed to negate the possibility that natural disease resulted in Ms Salihin's death.

"The less than optimal quality autopsy has failed in its primary duty to the deceased and her family, the accused and the justice system, which is to provide, as definitively as possible, a cause of death," he said in a statement to the court.

Queensland forensic pathologist Professor Beng Beng Ong and forensic toxicologist Michael Robertson had earlier also cast doubt on the prosecution's central claim that Ms Salihin had been fatally poisoned.

All three are expert witnesses for the defence.

"These [toxicology] results show there is no evidence of cyanide ingestion," said Dr Robertson, who was also an expert witness in the murder trial of former Brisbane real estate agent Gerard Baden-Clay.

Professor Ong, who was questioned about his visa status in court, was deported after giving evidence and banned from returning to Indonesia for six months because he had entered the country on a tourist visa.

The prosecutors also sought to discredit Dr Robertson by asking him about a salacious 2014 Daily Mail story that described him as the former lover of Kristin Rossum, who was convicted of murdering her husband in San Diego in 2000.

Dr Robertson told the court he understood the story was about him, but when asked if it was correct said: "I am not aware if the information is correct because it is from an internet website."

The alleged murder has fuelled endless speculation and turned into a media circus, especially given the beauty and youth of the two women, who studied together at the Billy Blue College of Design in Sydney, and the lack of an obvious motive.

At least two television stations broadcast live from the courtroom, with the trial reportedly bringing a boost in ratings.

Armchair observers weigh in on everything from Ms Wongso's "always cool face", as one 60-year-old housewife described it to The Jakarta Post, to the surge in popularity of Vietnamese iced coffee in cafes throughout Jakarta.

With Karuni Rompies

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