The wealthy ex-diplomat, who was facing murder charges, was found hanged in his Vienna prison cell in February 2015 just before he was due to testify in a separate extortion trial.
Experts at the time ruled his death to be suicide, but his widow and lawyers insisted foul play was involved.
A renowned German specialist, Bernd Brinkmann, has now sided with the family and found that “suicide was not possible”, Aliyev's lawyers said at a press conference in Vienna.
“His medical findings are very clear: anything other than murder can be ruled out,” one of the lawyers, Klaus Ainedter, later told AFP.
Authorities last year determined that Aliyev, 52, used strips of gauze bandages to hang himself from a coat hook in the bathroom of his cell.
But according to Brinkmann — also in attendance at the press conference — bruising on the neck indicated that someone had sat on Aliyev's chest and suffocated him by covering his mouth and nose.
The lawyers said they hoped the case would be reopened on the basis of the new evidence.
The prosecutor's office confirmed it had received a copy of Brinkmann's report and was waiting for a second expert opinion.
“We should have it by the end of the year,” spokeswoman Nina Bussek told AFP.
Aliyev, who used to be ambassador to Vienna, had turned himself in to Austrian police in 2014 over the killing of two bankers, kidnapped in Kazakhstan in 2007 and found dead four years later.
Denying the murder charges, the controversial businessman was due to go on trial in April 2015.
He died just before his scheduled testimony in a separate trial of two fellow inmates who he alleged had threatened to kill him and make it look like suicide unless he paid them money.
Aliyev often talked about his fear of being murdered, even after he stopped sharing a cell with other inmates, a police officer testified at the extortion trial last year.
The businessman had made a name for himself after marrying the eldest daughter of Kazakhstan's autocratic leader Nursultan Nazarbayev in the 1980s.
Aliyev held top government roles until he fell out with Nazarbayev, was stripped of his posts and ended up divorced.