A Russian court has opened the fraud trial against Sergei Magnitsky, a lawyer who died in prison in 2009 after accusing state officials of a multimillion-dollar tax scam.

The posthumous trial on Monday was initially scheduled for last December, but the judge adjourned the hearing after his family's defence lawyers refused to participate, saying trying a dead man was illegal.

Because no lawyer for the Magnitsky family showed up, the judge ordered the lawyers association to appoint a defense attorney for the next preliminary hearing on February 18.

"Participation in this process is illegal and immoral," Nikolay Gorokhov said in an interview with Al Jazeera's Emma Hayward.

"Sergei Magnitsky's mother and I characterise it as dancing on the bones of a dead man because you can not prosecute someone who is dead."

The whistleblowing lawyer's family has also refused to participate saying it is politically motivated.

"I think it is inhuman to try a dead man," Magnitsky's mother Natalya told Reuters news agency by telephone. "This is not a court case but some kind of farce, and I will not take part in it."

Magnitsky was 37 when he died after 358 days in jail, during which he said he was denied treatment as his health declined. The Kremlin's own human rights council aired suspicions he was beaten to death.

Russian authorities said he died of a heart attack, but his former employer, investment fund Hermitage Capital, says he was killed because he was investigating a $230m theft by law enforcement and tax officials through fraudulent tax refunds.

Relatives and former colleagues including Hermitage owner William Browder, who also faces trial in absentia, say Magnitsky was investigated and jailed by some of the same mid-level officials he told authorities had defrauded the state.

US legislation

Nobody has been convicted of any crime in connection with Magnitsky's death. One prison official was tried last year but prosecutors asked the court to clear him after President Vladimir Putin said Magnitsky had not been tortured, and the judge complied.

Prosecutors filed charges against Magnitsky and Browder last year, shortly before the US adopted the Magnitsky Act, a legislation imposing sanctions on Russians believed to be involved in his death or other grave human-rights abuses.

Russia responded with a law banning Americans from adopting Russian children, adding to tension that has increased since Putin's return to the presidency last May.

Browder, who lives in Britain, has also said he would not participate. He was one of the biggest Western investors in Russia but was barred from the country in 2005 as Hermitage found itself coming under increasing official pressure.

Judges use preliminary hearings to address procedural motions and set a trial date. If Magnitsky's relatives do not hire a lawyer to defend him, the court will appoint one, state-run news agency RIA reported.

Amnesty International, the UK-based rights group, said the planned trial of Magnitsky was an "attempt to deflect attention from those who committed the crimes he exposed".

It would set "a dangerous precedent that would open a whole new chapter in Russia's worsening human rights record", the group's regional director, John Dalhuisen, said in a statement.