A Moscow court on Thursday sentenced in absentia the US-born British investor who was the former boss of dead lawyer Sergei Magnitsky to nine years in a prison colony after being convicted of tax evasion.

William Browder, the head of the Hermitage Capital investment fund, was sentenced by a Moscow court which had earlier already convicted Magnitsky in the same case.

However no sentence was issued for Magnitsky after the court decided to halt the case against him owing to his death.

The trial of a dead person is almost unprecedented in post-Soviet Russia, and has raised concerns that that judicial authorities continued to persecute Magnitsky because of the furore over his death.

An empty cage in the courthouse -- where normally the defendant hears the verdict -- symbolised the absence of the late Magnitsky and Browder.

"I did not doubt that the decision would look like this," the lawyer for Magnitsky's family Dmitry Kharitonov told the RAPSI legal news agency. "I know that he committed no crimes."

Magnitsky had accused interior ministry officials of organising a $235-million tax scam, but was then charged with the very crimes he claimed to have uncovered.

He was placed under pre-trial detention in 2008 and died of untreated illnesses less than a year later at the age of 37.

Browder, who is now based in London, insists Magnitsky was tortured to death with beatings and the refusal of proper medical care.

His death led to one of the biggest Washington-Moscow rows in years with the US late last year passing the "Sergei Magnitsky Act" which imposed a visa ban and froze the assets of Russian officials implicated in the lawyer's death.

The legislation infuriated Moscow, which in retaliation passed legislation prohibiting Americans from adopting Russian children.

Russia's Constitutional Court made it possible to try deceased people under a July 2011 ruling that allowed families of late defendants to push for their exoneration by the courts.