Dmitry Kovtun was one of two Russian men accused by Britain of poisoning Litvinenko. The ex-KGB officer died after drinking green tea laced with radioactive polonium-210 in 2006. Kovtun and Andrei Lugovoy denied carrying out the killing. Dmitry Kovtun, one of two Russian men accused by Britain of poisoning Kremlin critic Alexander Litvinenko in London in 2006, has died of