The Federal Prison Service on Thursday admitted that it was partly guilty for the death in custody of a lawyer whose supporters say was an innocent victim in a battle between the Interior Ministry and an investment fund.

Sergei Magnitsky, a 37-year-old lawyer for Hermitage Capital Management, once the biggest Russian equity fund, died Nov. 16 in the hospital of a Moscow prison from what prosecutors said was heart failure.

Magnitsky’s lawyers said he was kept in custody illegally and not given proper medical treatment despite repeated requests for help.

“There were clear violations from our side there. We will not deny them. But I do not want to make any conclusions yet,” said Alexander Smirnov, a deputy director of the prison service, Interfax reported.

“We are not in any sense playing down our guilt, which clearly exists,” he told members of the Public Chamber.

The comments, which amount to the first admission by a Russian official of any complicity in the death, came after President Dmitry Medvedev on Tuesday ordered the Prosecutor General’s Office and the Justice Ministry — which oversees the prisons service — to investigate.

The prosecutors’ Investigative Committee announced hours later that it had opened a criminal negligence investigation.

Magnitsky was a witness for Hermitage in its contention that corrupt officials embezzled $230 million in tax refunds. Police arrested him in 2008 and accused him of involvement in alleged tax frauds by Hermitage, though the case never went to trial.

After Magnitsky’s death, Hermitage chief William Browder made public one of his letters describing harrowing prison conditions and expressing frustration at being unable to see his mother and wife or to speak to his two children during nearly a year behind bars.

Browder said Magnitsky was arrested by the same Interior Ministry officers implicated in the alleged fraud.

The American Chamber of Commerce in Russia sent a letter to Medvedev on Wednesday expressing support for his order and calling for a “fair and transparent investigation” into Magnitsky’s death.

The main detective unit of the Interior Ministry on Wednesday denied Browder’s accusations that senior policemen were involved in the fraud and said the crime had been successfully solved.

“Where did you get the idea that certain employees of the Interior Ministry were involved in this,” said Irina Dudukina, spokeswoman for the Interior Ministry’s investigative committee, when asked about Browder’s allegations.

Dudukina said Magnitsky had been in good health when arrested in 2008 and that detectives had not noticed any health problems when questioning him.

The prison service’s Smirnov said the Magnitsky case had put a “serious stain” on Russia’s judicial system and that the results of an internal probe would be made public soon.

The press service for the prison service did not answer repeated telephone calls seeking comment.

(Reuters, AP)