The toxin was found in the body of the Russian dissident Aleksei A. Navalny, who died in prison two years ago, five governments said, challenging Russia’s official account.

Brian Walton of Los Angeles faces multiple charges in the murder of 23-year-old Claudia Guevara, whose body was found in a drainage ditch next to Encanto Parkway in Azusa on Feb. 21, 1996.

Russian opposition figure and outspoken Kremlin critic Alexey Navalny, who died two years ago, was killed while in prison by a lethal toxin found in poison dart frogs in South America, five European ...