A Moscow court on Thursday convicted dead Russian lawyer Sergei Magnitsky of tax evasion, provoking outrage over the posthumous prosecution of a man whose death in pre-trial detention led to a major diplomatic row with Washington.

Magnitsky was convicted along with his former boss, the US-born British citizen William Browder, the head of the Hermitage Capital investment fund who was sentenced in absentia to nine years in a prison colony.

However the case against Magnitsky ended with his verdict and a refusal to exonerate him, as the authorities cannot take a case against a dead man any further.

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

Journalists packed the tiny courtroom of the Tverskoy district court in central Moscow where the judge read the verdict so quietly that it could only be heard through headphones of television crews with microphones.

The metal cage, where defendants normally hear the verdict, stood symbolically empty of either the late Magnitsky or Browder, who is based in London.

Browder, who has overseen for several years a campaign to bring to justice officials who were implicated in Magnitsky’s death, vowed to continue his efforts despite the conviction.

“Today’s verdict will go down in history as one of the most shameful moments for Russia since the days of Joseph Stalin,” Browder said in an emailed statement.

“The desperation behind this move shows the lengths that Putin is ready to go and to retaliate against anyone who expose the stealing and corruption he presides over,” Browder added.

President Dalia Grybauskaite of Lithuania, which had assumed the presidency of European Union this month, said the ruling was “symbolic and should be assessed negatively.”

“The very fact that there is a conviction worries us as it is a symbolic act showing the level of human rights violations and the deteriorating situation of ensuring human rights in Russia,” Grybauskaite told reporters in Vilnius.

Magnitsky had accused interior ministry officials of organising a $235-million tax scam against Browder’s investment company Hermitage Capital, but was then charged with the very crimes he claimed to have uncovered.

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

Browder and many Russian rights campaigners have said that Magnitsky was tortured to death with beatings and the refusal of proper medical care.

However after Putin said late last year that Magnitsky died of a heart attack, Russia dropped the probe into his death citing “lack of evidence” and acquitted an official of Moscow’s Butyrka prison where the man was held.

The mother and widow of the lawyer have boycotted the trial hearings and asked Moscow’s legal community to do the same, but the judge appointed two lawyers to the case at risk of disbarment. But the lawyers distanced themselves from the process and shied away from the press.

“I have not been authorised (by the family) to do anything, so I will say nothing,” Nikolai Gerasimov, who was appointed to represent Magnitsky, told reporters after the trial. Browder’s defence lawyer Kirill Goncharov said he will appeal the verdict.

Magnitsky’s 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 move 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.