A Moscow court on Thursday convicted Russian lawyer Sergei Magnitsky of tax evasion, provoking fresh outrage more than three years after his prison death, AFP reports.
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 the 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 was almost unprecedented in post-Soviet Russia, raising concerns the judicial authorities under Putin had continued to persecute Magnitsky because of the political furore over his death.
Washington criticised the court's ruling in a case that has strained relations between the two countries.
"We are disappointed by the unprecedented posthumous criminal conviction against Sergei Magnitsky," State Department spokeswoman Jen Psaki.
"The trial was a discredit to the efforts of those who continue to seek justice in his case."
Russia's authorities should instead have prosecuted those responsible for his death, she added.
Rights group Amnesty International denounced the posthumous verdict as the "pinnacle of absurd". Convicting a dead man instead of investigating how he died set a "dangerous precedent", it said.
Journalists packed the tiny courtroom of the Tverskoy District Court in central Moscow where the judge read the verdict so quietly it could only be heard through headphones of television crews with microphones.
The metal cage, where defendants normally hear the verdict, stood empty. Browder is based in London.
The financier, who for several years has overseen a campaign to bring to justice officials 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," he 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 exposes the stealing and corruption he presides over."
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 said he had 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 and many Russian rights campaigners have said 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 dead man's mother and his widow 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.
"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 would appeal the verdict.
President Dalia Grybauskaite of Lithuania, which assumed the presidency of the European Union this month, said the ruling was "symbolic and should be assessed negatively."
Magnitsky's death led to one of the biggest Washington-Moscow rows in years.
Late last year the US passed 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.
The first posthumous conviction was handed down just last week when a Moscow court convicted a woman of causing a head-on car collision in 2010 in which she was killed.
Olga Alexandrina was behind the wheel when she collided with the car of an oil executive. Her family had tried to have her exonerated by arguing that she had stayed in her lane while the executive's car swerved into oncoming traffic.