MOSCOW: A Russian court on Monday held a new preliminary hearing in the posthumous fraud trial of dead investment fund lawyer Sergei Magnitsky in defiance of his family who claimed it had no right to appoint defence lawyers.

The Tverskoi District court in central Moscow, in a third preliminary hearing in the trial, adjourned the case to March 4 at the request of defence lawyers who Magnitsky's mother said had no right to defend her son.

"The preliminary hearing has been postponed to March 4 at the defence's request," a court spokeswoman told AFP, declining to name the lawyers appointed by the court to defend Magnitsky and his former employer, Hermitage Capital chief William Browder, who is being tried in absentia.

Hermitage Capital investment fund attorney Magnitsky died in pre-trial detention in 2009 after being arrested and charged by the very same senior officials he had accused of organising a $230-million fraud scheme.

The case has come to symbolise the Kremlin's failure to crack down on corruption and has further added to tensions with Washington following the US decisions to blacklist Russian authorities implicated in the case.

Magnitsky's mother Natalya, who along with her own lawyers is boycotting the trial, said the court-appointed defence lawyers should be fully aware they were legitimising an unfair process with their presence.

"Any lawyer asked to appear at the hearing.... may not realise the unlawfulness of the posthumous prosecution of my son," she said in a statement released by Hermitage Capital.

"Any lawyer's presence will allow the court to indicate the absence of violations of the right to defence, and thus through his presence the lawyer will serve as an unwitting accomplice to this crime."

Hermitage Capital says Russia's decision to prosecute Magnitsky after his death -- a rare move which the prosecution argues is allowed by the law -- has pushed the case into the realm of the absurd.

"The fact that this posthumous trial is going ahead indicates that justice in Russia is turning into raw and outright blasphemy," it said in a statement.

The Russian authorities reopened the case against Magnitsky nearly two years after his death in what Hermitage Capital claims is a bid to deflect attention from the real culprits in the tax fraud. The

The law has prompted a crisis in US-Russia ties, with Moscow retaliating by banning US adoptions of Russian orphans.