To Mr. Borshchev, there was only one way to interpret this: the prisoner was refusing to cooperate. Indeed, Mr. Magnitsky’s job at a Russian-American law firm drew him into a battle between William F. Browder — once the largest foreign investor in the Russian stock market — and the Interior Ministry, which oversees law enforcement. In 2007, Mr. Browder’s company, Hermitage Capital, based on Mr. Magnitsky’s research, accused police investigators of an immense act of corruption, charging that they had seized three of Mr. Browder’s subsidiary companies and used them to receive a $230 million tax refund.

The next year, the Interior Ministry charged Mr. Browder’s companies with evading $17.5 million in taxes. As soon as Mr. Magnitsky was arrested, investigators were pushing him to testify against someone, presumably Mr. Browder, said his defense lawyer, Dmitri V. Kharitonov. But he refused.

The commission’s narrative flowed with some logic until it reached Nov. 16, 2009, the day he died. The nervous doctor sent Mr. Magnitsky to another prison, which had a hospital. There, the oversight panel met a surgeon named Dr. Aleksandra V. Gaus, who said she noted upon his arrival that he had symptoms of acute pancreatitis and prepared to send him for treatment.

At 7 p.m., Dr. Gaus said, he started to act erratically, and she changed her mind, determining that he was suffering from “acute psychosis and persecutory delusions.” She called a team of eight guards to forcibly subdue him, and they handcuffed him to the bed in an isolation cell to wait for a psychiatric emergency team. An hour and a half later, officials said, he collapsed when the psychiatrist was examining him, and was rushed to intensive care for resuscitation. He was declared dead at 9:50 p.m.

Mr. Borshchev was mulling over this account when he got a startling phone call. A few days earlier, he had left his card for the psychiatrist who was present at Mr. Magnitsky’s death. On the phone was the psychiatrist, Dr. Vitaly V. Kornilov, who told a different story: He and his team had been forced to wait at the clinic’s outer gates for a full hour — roughly from 8 until 9 p.m. — before they were allowed inside.

By the time he entered the cell, as Dr. Kornilov would later tell the official investigators, “we were presented with the fact that we could not carry out a psychiatric examination because of the lack of a patient.”