Mr Magnitsky was arrested in 2008 after accusing officials of tax fraud but was later himself accused of those crimes.
His death in custody a year later led to a major diplomatic dispute between Russia and the United States.
William Browder, the CEO of London-based Hermitage Capital Management which Mr Magnitsky represented, is also accused of tax fraud.
Russian prosecutors are asking Moscow's Tverskoi district court to convict Mr Magnitsky and then immediately dismiss the case because of his death.
It is believed to be the first time in Soviet or Russian history that a defendant will have been tried posthumously.
Mr Magnitsky's relatives regard the case as illegal.
Employed as an auditor for Hermitage, Mr Magnitsky uncovered what he described as a web of corruption involving Russian tax officials, including the alleged theft of more than $200m (£125m).
After reporting the allegations to the authorities, he was himself detained on suspicion of aiding tax evasion.
He had pancreatitis and died in custody in 2009, but an investigation by Russia's presidential council on human rights concluded that he had been severely beaten and denied medical treatment.
Last December, a Russian court acquitted a prison doctor accused of negligence over Mr Magnitsky's death.
The Russian prosecutors are also pressing for Mr Browder to be sentenced in absentia to nine years in prison on the same tax fraud charges.
The US-born fund manager, who is now a British citizen, denies the charges.
He has spearheaded efforts in the US to put pressure on Russia over the Magnitsky case.
Last year, the US passed the Magnitsky Act, blacklisting Russian officials accused of human rights violations.
In response, Russian President Vladimir Putin signed a law barring Americans from adopting Russian orphans.