Following a two-day inquest Berkshire coroner Peter Bedford said he was not certain what caused Mr Berezovsky, 67, to die at his home in Mill Lane, Ascot, last year.
Detective Inspector Mark Bissell said tests confirmed Berezovsky had been hanged from a shower rail, and concluded he hanged himself with no third party involvement.
However Professor Bernd Brinkmann - a friend of the family who specialises in hanging and asphyxiation cases - told the inquest today that the marks on Mr Berezovsky’s neck could not have come from hanging.
He argued an unknown assailant strangled Mr Berezovsky with his scarf before hanging him from a shower rail.
Pathologist Simon Poole said he believed there was no third party involvement, and toxicology reports showed no poisons were involved in Mr Berezovsky’s death.
Mr Berezovsky’s bodyguard Avi Navama told the inquest Mr Berezovsky was “very depressed” in the months leading up to his death.
He had previously lost a £3 billion claim against Chelsea Football Club owner Roman Abramovich, and Mr Navama said Berezovsky - born Elenin Platon - told him he was £200m in debt.
Berezovky’s personal assistant, Michael Cotlick, said he had seen a change in Berezovsky’s personality following the trial.
Earlier Mr Berezovsky’s daughter, Elizaveta, said her father believed he had been poisoned.
In a statement, Berezovsky’s former wife Galina Besharova said her ex-husband did not plan to kill himself, adding she could not believe he would have committed suicide.
Recording an open verdict at Windsor Guildhall, Mr Bedford said he could not be sure whether Mr Berezovsky had committed suicide or had been killed in another way.