Ed Bentley and Anna Arutunyan

The sudden death of imprisoned lawyer Sergei Magnitsky last week has cast a dark cloud over Russia's already-controversial human rights image, as well as dragging a messy business dispute back into the limelight.

Following Russia's 2005 refusal of re-entry to Hermitage Capital's CEO, William Browder, whom Magnitsky represented, the spat between the hedge fund and a group of Interior Ministry officials has escalated in a series of accusations and counter-accusations.

Browder and relatives of the 37-year-old lawyer claimed he had paid the ultimate price, and accused Interior Ministry officers of complicity in his death.

"He went into prison a healthy 37-year-old man and came out dead," Browder said in a telephone interview from London. "Thirty-seven-year-old men don't just die, particularly when he was regularly complaining about a lack of medical attention to a very serious condition."

Prison officials say Magnitsky died as a result of heart failure, although RIA Novosti cited his lawyers saying a rupture of the pancreas was to blame.

"We found out that he died from ... toxic shock, which is what happens when your digestive system ruptures," said Jamison Firestone, a partner at Firestone Duncan, the law firm where Magnitsky worked.

In notarised documents that Hermitage Capital has now posted on the Internet, the lawyer lists every complaint he made, as well as a copy of a letter to Prosecutor General YuryChaika. Since being in pre-trial detention Magnitsky claimed he had been diagnosed with gallbladder stones, calculouscholecystitis and pancreatitis.

Without treatment these conditions could lead to death from a ruptured digestive system, Britain's Telegraph newspaper reported.

"I was not provided with the prescribed medical examination, I was not given any medical advice with regard to my illness, I didn't get an appointment with a surgeon and no dietary plan was prescribed or even considered," Magnitsky wrote in the letter to Chaika.

A spokeswoman for the Interior Ministry's investigative committee denied that they had received any complaints about Magnitsky's health.

"There were no health complaints made to the investigator or the judge," Irina Dudukina said by telephone on Monday. "It is possible that he complained to the head of the detention centre with health concerns, but not to the investigator."

An investigation has been launched into Magnitsky's death by the investigation committee of the Prosecutor General's Office, while Dudukina said she expected the results of an autopsy to be made public in the next few days. Friends and supporters of Magnitsky's, however, have already cast doubt over the legitimacy of any investigation following his burial on Friday without an independent autopsy being carried out.

"If ... they really didn't want to do anything about Magnitsky's illegal incarceration, do I really have a lot of faith in a government investigation which is going to look into his death?" said Firestone.

The prosecutors' investigative committee declined to comment on Magnitsky's death.

The dispute between Hermitage, once Russia's largest hedge fund, and a group of Interior Ministry officials widened when the firm and its lawyers implicated officers in a $230 million tax fraud scheme, according to Firestone Duncan, the law firm.

"Some people have stolen hundreds of millions of dollars from the Russian treasury," said Firestone. "They didn't steal it from me, they didn't steal it from my client, they stole it from the treasury."

In 2007, Hermitage's offices were raided. Magnitsky was arrested on Nov. 14, 2008, on charges of helping Hermitage Capital to evade $3.25 million in taxes, while an extradition request is still out for Browder.

Magnitsky's year-long imprisonment in the Butyrskaya and Matrosskaya Tishina pre-detention centres also angered international legal bodies, who claim it violated the European Convention for Human Rights, which Russia is a party to.

"The treatment of lawyers related to Hermitage raises doubts as to Russia's efforts to foster the rule of law and establish a credible justice system," Marie Pierre Olivier from the International Bar Association's Human Rights Institute said in an e-mailed response to questions.

Russia's human rights activists have also criticised the situation in Russia's prisons, saying that violence, neglect and refusal of medical care to prisoners, particularly outside of the capital, is commonplace.

"The death of a man in Moscow who has not been convicted - this is rare," said Lev Ponomaryov, leader of the For Human Rights group. "It shows just how critical the general penal situation has become."

This latest twist in the Hermitage saga has dragged it back into investors' attention at a time when President Dmitry Medvedev has made tackling corruption and legal nihilism one of his priorities.

A Kremlin press officer, speaking on condition of anonymity, denied that Magnitsky's death or the Hermitage case would affect Medvedev's drive for strengthening the rule of law and said a host of legal measures were already being implemented to strengthen the justice system.

"It is not up to the Kremlin to rule on every case, it is not to fair to blame every single negative fact that happens in the country and blame it on the government," the press officer said.

It would, however, take time for Medvedev's legal reforms to take full effect, the spokesman added.

Gleb Pavlovsky, head of the pro-Kremlin Effective Politics Foundation, said that conditions were  an "outrageous degradation of the prison system".

"I was in a similar cell in the early 80s and based on Magnitsky's description I can say that under Brezhnev conditions were better - there were toilets," he said.

"Society should note that this is unacceptable.

"The case should speed up Medvedev's plans for modernisation."

Before Browder was refused entry into the country, and even for a short time afterwards, the Hermitage CEO was an ardent supporter of Putin's and an outspoken advocate of investing in Russia - even when other some other investors criticised the Kremlin over the Yukos affair.

"Vladimir Putin has shown himself to be a nationalist in the good sense of this word," Browder said in a 2005 interview with Expert published on the Hermitage website. "During his period in office, economic policy has been consistent with national interests."

Since then his position has turned 180 degrees, claiming that the tax evasion charges against Hermitage were a response to his firm implicating Interior Ministry officers in the $230 million tax fraud scheme.

Although a former saw mill worker, Viktor Markelov, was arrested over this crime, Browder described it as "fig leaf to cover up the involvement of higher-ups," adding that corruption ran throughout the system.

Despite Medvedev's tough stance on corruption, Magnitsky's colleagues believe the situation is worsening, following the recent high-profile deaths of human rights campaigners Natalya Estemirova, Stanislav Markelov and Anastasia Baburina.

"Russia does not have rule of law and Russia is moving in the wrong direction," said Firestone. "The law enforcement agencies are the new mafia and everybody knows it."