The details of the killing given by Felix Yusupov have never stood up to scrutiny. He changed his account several times; the statement given to the St. Petersburg police on December 16, 1916, the accounts given whilst in exile in the Crimea in 1917, his 1927 book, and finally the accounts given under oath to libel juries in 1934 and 1965 all differ to some extent, and until recently no other credible, evidence-based theories have been available.
According to the unpublished 1916 autopsy report by Professor Kossorotov, as well as subsequent reviews by Dr. Vladimir Zharov in 1993 and Professor Derrick Pounder in 2004/05, no active poison was found in Rasputin's stomach. A possible explanation would be that the cyanide in the cakes had vaporized due to the high temperatures during the baking in the oven.
It could not be determined with certainty that he drowned, as the water found in his lungs is a common non-specific autopsy finding. All three sources agree that Rasputin had been systematically beaten and attacked with a bladed weapon, but, most importantly, there were discrepancies regarding the number and caliber of handguns used.