An initial toxicological test on Aliyev showed traces of barbiturates, although a final autopsy report has not yet been released.
The barbiturates discovered are a kind of sedative that are not prescribed by doctors in Austria, according to one of Aliyev's lawyers, Manfred Ainedter. He has said that the case has too many inconsistencies, and is filing a criminal complaint against two officials from the Federal Criminal Police Office, after an alleged correspondence with the law firm Lansky.
Lansky represents a Kazakh victims' association called Tagdyr, which in turn represents the widows of the two Kazakh bankers Aliyev was accused of murdering in 2007.
Aliyev always maintained that the murder charges were politically motivated and trumped up by rivals in his homeland. Lansky has said the allegation is a “red herring”.
On the day of his death, Aliyev, 52, a former ambassador, had been due to testify against other inmates who he said had blackmailed and threatened to kill him while making it look like suicide.
Authorities say video footage and electronic door control systems showed no unauthorized people had entered Aliyev's solitary confinement cell before his death.
Meanwhile a second autopsy has been ordered, with Austria's Justice Minister Wolfgang Brandstetter saying that Swiss forensic experts would be consulted.