A Belgrade court found the former head of Serbia's secret police, Radomir Markovic, guilty of trying to cover up a car crash in 1999 which aimed to kill Vuk Draskovic, leader of the Serbian Renewal Movement.
He is the most senior member of Mr Milosevic's inner circle to serve a jail sentence in Serbia since reformers took power in 2000.
Mr Draskovic survived the collision, in which a truck was said to have driven into his convoy, but his brother-in-law and three others travelling with him died.
Former secret police officials Nenad Bujosevic and Nenad Ilic, who drove the truck, were jailed for 15 years.
Relatives of the car crash victims are said to be infuriated, as they expected Mr Markovic to be held directly responsible for the assassination attempt on Mr Draskovic.
Previous sentence
The lawyer representing them, Vladimir Bozovic, described the verdict as "shameful".
Mr Markovic has been in prison since 2001 for revealing state secrets.
He had served his sentence but was kept in jail for the duration of the trial.
Mr Milosevic is currently being tried for war crimes at The Hague, Netherlands.
Appearing as a witness at the trial, Mr Markovic defended the former Yugoslav leader, saying he ordered the protection of ethnic Albanians in Kosovo.
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