A key witness in the poisoning death of former Russian security agent Alexander Litvinenko again failed to speak to investigators Friday, but his lawyer said his health wasn't preventing the interrogation, a Russian news agency reported. Andrei Lugovoi, who met with Litvinenko in a London hotel on the day the former KGB agent believed he was poisoned, has been due to testify since Tuesday after a team of Scotland Yard officers arrived in Moscow, but the interrogation has been postponed several times. Doctors at a Moscow clinic have been examining Lugovoi for any signs of illness due to possible exposure to radiation. The Interfax news agency on Friday quoted unidentified medical sources as saying that checks of Lugovoi had shown that some of his organs malfunctioned, apparently as a result of a radioactive substance. Lugovoi himself later told the ITAR-Tass news agency that he was feeling "normal."