Russian state culpable in Litvinenko death: UK lawyer LONDON (Reuters) - A lawyer at a preliminary hearing on the death of Kremlin critic Alexander Litvinenko said on Thursday that evidence existed to show the Russian state was culpable for poisoning him. Litvinenko, who had been granted British citizenship, died after he was poisoned with polonium-210, a toxic radioactive isotope, which was slipped to him in a cup of tea at a plush London hotel in 2006. An examination of government material establishes "a prima facie case in the culpability of the Russian state in the death of Alexander Litvinenko," said Hugh Davies, an attorney acting on behalf of the inquest. The full inquest, led by Judge Robert Owen, is expected to start on May 1, he said. The lawyer for Litvinenko's widow, Marina, told the pre-inquest hearing the victim had been working for Britain's Secret Intelligence Service, known as MI6, for a number of years. Moscow has in the past denied any involvement in the killing. Reporting by Dasha Afanasieva; editing by Mohammed Abbas; Editing by Angus MacSwan