Rakhat Aliyev, the Kazakh president's former son-in-law turned opponent, has been found dead in an Austrian jail from an apparent suicide, a court spokeswoman said on Tuesday.
"He committed suicide," the spokeswoman said.
Austrian prosecutors in December had charged him with the murder of two bankers in 2007, a case in which Kazakhstan has repeatedly requested his extradition.
Aliyev, once Kazakh ambassador to Austria who became a vocal critic of President Nursultan Nazarbayev, had denounced the case against him as politically motivated. He had been in custody since June when he turned himself in to Austrian authorities.