MOSCOW — The case of Sergei L. Magnitsky, the Russian tax lawyer who was imprisoned in 2008 on false charges and died in jail, began as a tragedy. But now, after years of sanctions, countersanctions, bitter feuds and one noteworthy meeting in Trump Tower, the case seems to be entering the realm of farce.

Mr. Magnitsky, who worked for William F. Browder, a hedge fund manager who was once the largest foreign portfolio investor in Russia, was jailed on tax evasion charges while unraveling a $230 million government tax “refund” that Russian officials had fraudulently granted themselves. He died in prison after being beaten and denied medical care, earning the Kremlin widespread condemnation.

Mr. Browder, who was living in London at the time, began lobbying Western governments to punish those responsible for Mr. Magnitsky’s death, an effort that bore fruit when the United States, Estonia and most recently, Canada, imposed sanctions on Russians involved in Mr. Magnitsky’s death.

That campaign touched off a nasty confrontation with the Kremlin, and the two sides have been trying ever since to undermine the credibility of the other. Recently, however, Russian prosecutors have taken that effort to a remarkable new level, claiming that Mr. Magnitsky was actually murdered by Mr. Browder.