Alexander Zemlianichenko/AP Photo

MOSCOW - A Russian court today convicted a whistle-blowing auditor of tax fraud nearly four years after his death.

Sergei Magnitsky was posthumously convicted of embezzlement, charges his supporters say are politically motivated. Also convicted in absentia was William Browder, the head of Hermitage Capital, once one of largest foreign investors in Russia and Magnitsky's client. Browder was sentenced to nine years in prison for tax evasion, but remains in London.

Browder has become been one of Magnitsky's loudest defenders.

"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 a statement after the verdict was announced.

"The desperation behind this move shows the lengths that [Russian President Vladimir] Putin is ready to go any to retaliate against anyone who expose the stealing and corruption he presides over," Browder said. He vowed to continue to "fight for justice for Sergei Magnitsky and his family until the job is done."

Magnitsky died in a detention center in 2009 at the age of 37. The cause of his death remains in dispute. His death has been attributed to a pancreatic condition that was not treated in prison. Human rights advocates also say there is evidence he was beaten to death. So far, nobody has been charged with any wrongdoing in his death.

Magnitsky was auditing Hermitage Capital's accounts when he uncovered evidence he said showed Russian officials and police were stealing around $230 million in tax refunds. After exposing the evidence, Magnitsky was arrested and charged with fraud himself.

Magnitsky's case became a cause célèbre among human rights activists and some on Capitol Hill as a sign of Russia's poor human rights record and corrupt courts. Last December, Congress passed a set of human rights sanctions on Russian officials named after Magnitsky. That led Russian lawmakers to pass a retaliatory bill that included a controversial ban on adoptions to the United States.