No plant toxins were found in a Russian businessman who it was claimed may have been poisoned, a coroner has heard.
Alexander Perepilichnyy's inquest also heard conflicting reports about whether he "feared for his life" before his sudden death in November 2012.
The businessman, who was a whistleblower in a $230m (£150m) money-laundering case, was found near his home in Weybridge, Surrey.
The inquest resumed at the Old Bailey after being paused in June 2017.
Coroner Nicholas Hilliard QC previously heard two post-mortem examinations failed to find a cause of death but it was possible a poison derived from a plant may have been in his system.
But Professor Monique Symmonds, a botanist at the Royal Botanic Gardens in Kew, told the inquest she had not been able to identify any plant toxins in the specimens she tested.
Suspicion had been raised by a high level of iron in a sample from his stomach but no traces of a toxin which might have caused it were found, the inquest was told.
Mr Hilliard also heard from a corporate lawyer who represented Mr Perepilichnyy in several "very complicated" debt cases in Russia.
Dimitry Lipkin said his client missed a court case in Russia in March 2011 because he was "fearful for his life" if he returned to his homeland.
The Russian court did not ask for any further evidence about the threats and Mr Lipkin said he had no further information on who Mr Perepilichnyy was fearful of or why.
Mr Perepilichnny won the case against loans recovery company Dzhirsa, Mr Lipkin said, and died a month after the firm lost its appeal.
'Nonsense and absurdity'
Dzhirsa has previously been linked with Dmitry Kovtun, one of the alleged killers of the former Russian spy Alexander Litvinenko, the inquest heard.
Extracts from an article in the Daily Telegraph in 2012, in which Mr Kovtun said he was the firm's founder, were read out in court.
The inquest also heard from two of Mr Perepilichnyy's brothers-in-law and a Swiss lawyer all of whom said they did not believe he was fearful.
Ruslan Gursky, a brother-in-law who lives in Ukraine, said speculation about the deceased was "highly dubious" while Rishat Ismagilov, whose sister was married to Mr Perepilichnyy, said claims the family had fled to the UK were "false".
In a statement read to the inquest, Mr Ismagilov said the coroner should confine himself to finding a cause of death with any further investigation into claims about Mr Perepilichnyy's life being a "logical nonsense and legal absurdity".
Both men said Mr Perepilichnyy was jogging more to lose weight.
The Swiss lawyer Francois Roger Micheli, who had met with the Russian as part of the money-laundering investigation, also told the inquest "at no moment did [Mr Perepilichnyy] indicate he felt threatened or unsafe".
The inquest continues.