Police investigating the death of a Russian whistle-blower lost evidence of threats, multi-million pound bank transfers and links to a major money laundering scheme, an inquest heard.
A civilian police translator said she flagged up the material while going through logs taken from the computer of Alexander Perepilichnyy, who died while jogging near his home in Weybridge in November 2012.
But two disks which were thought to contain the evidence were later found to be blank with no copies made, Coroner Nicholas Hilliard QC was told at London’s Old Bailey.
The inquest is trying to establish whether the 44-year-old died of natural causes or was murdered.
Lucas Fear-Segal, for Perepilichnyy’s life insurers Legal and General, told translator Ekaterina Clarke-O’Connell: “Essentially, the original documents you looked at have gone missing.
“It’s either the fault of Surrey Police or South East Counter Terrorism Unit (Sectu) and back-up cannot be accessed by Surrey Police so all we have got is you.”
Asked to recall documents she saw, Ms Clarke-O’Connell said: “They were work-related to the deceased. We were given trigger words that could show threats, anything unusual, money laundering activities, some names.”
She added: “I have seen large sums of money going in and out of different accounts… If you think to see something suspicious, these large sums of money, as a human, you think something is not right. My job was to flag up something mentioning large sums of money, which I did.”
Asked to recalled figures, she said sums of £310 were being moved through accounts.
She also revealed she found threatening text messages.
One demanded Perepilichnyy pay the equivalent of £6,000 in roubles or face prison, she said. Another threatened him not to “do anything silly because we have everything under control”.
Ms Clarke-O’Connell also confirmed she found nothing to indicate the father-of-two’s health was of concern.
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At the time he died, Perepilichnyy was helping UK-based Bill Browder’s Hermitage Capital Investment to expose a $230 million (£142 million) money laundering operation.
He was also fighting a legal challenge by a debt recovery firm allegedly led by Dmitry Kovtun, the prime suspect in the killing of Alexander Litvinenko – a high-profile Russian defector who was poisoned in London in 2006.
But in December 2012, investigating officer Detective Superintendent Ian Pollard told the Home Office that he found no connection between Mr Perepilichnyy and Mr Kovtun.
He said he did not know at the time Mr Kovtun was linked to the debt recovery firm Jsa, which brought the lawsuits, adding that he did not make inquiries abroad as “there is no evidence of murder or poison”.
The inquest had previously heard that Mr Perepilichnyy violently vomited after a restaurant meal with secret girlfriend Elmira Medynska in Paris the night before he died.
The inquest continues.