Protesters hold protest signs denouncing Russian President Vladimir Putin near the Russian permanent mission to the United Nations in New York. (Reuters)
The fatal shooting in Moscow last week of a Russian opposition leader, Boris Y. Nemtsov, has prompted comparisons with the 2006 poisoning of Alexander V. Litvinenko, another foe of President Vladimir V. Putin, who fled to Britain in 2000 and secured British citizenship weeks before he died of what was almost the perfect poisoning.
On Monday, the 18th day of testimony in a public inquiry into Litvinenko's death in November 2006, physicians gave a detailed chronology of Litvinenko's inexorable decline, reinforcing previous assessments that the cause of his death may never have been discovered if it had not been for tests carried out at a top-secret British facility hours before he died.
As Litvinenko lay dying, physicians struggled to come up with a diagnosis. His blood counts spiraled down, his hair came out in clumps and his bone marrow ceased to function.
The symptoms, one specialist said, resembled those of a cancer patient battling the side-effects of chemotherapy and radiation. Some doctors thought the cause of Litvinenko's illness was thallium poisoning, and treated him with an antidote called Prussian blue. But the patient's heart weakened and his liver and kidneys stopped functioning.
Only a day before Litvinenko died on Nov. 23, 2006, did scientists conclude that he was the victim of radiation poisoning caused by a large dose of polonium 210, an isotope manufactured mostly in Russia.
"It's a different way to kill a person," Litvinenko's widow, Marina, told the BBC last weekend, referring to Nemtsov's death, perhaps at the hands of political opponents, "but a way to present that anybody who will try to say something against us will be killed."
Until shortly before his death, the diagnosis was that Litvinenko, 43, had been poisoned with thallium. But Litvinenko showed no sign of muscle weakness - a key indicator of thallium poisoning.
"I was becoming convinced that it was not thallium poisoning, but didn't know what it was," said Dr. Amit Nathwani, a consultant at the University College Hospital in London where Litvinenko was transferred after initial treatment at Barnet in north London.
As Litvinenko worsened, scientists at Porton Down, a British government research facility, were working on pinpointing the toxin from a sample of his urine. But it was only on the night before Litvinenko died, Nathwani said, that an expert from the facility called him and, for the first time, said polonium was a possibility.
The identification of the isotope was critical since it enabled the police to follow what became known as the "polonium trail," linking Litvinenko to two Russians accused of killing him, Andrei K. Lugovoi and Dmitri V. Kovtun, who both deny the charge. The British police say that Litvinenko was poisoned after drinking green tea laced with polonium at a bar in central London where he met Lugovoi, a former KGB bodyguard, and Kovtun, a former Red Army soldier, on Nov. 1, 2006.
The delay in discovering polonium resulted from a feature of the isotope itself. Polonium emits mainly alpha radiation while the Geiger counter used to check Litvinenko for radiation poisoning detected gamma radiation.
Indeed, a report at the Barnet hospital on Nov. 15, 2006, said there were "no radioactive emissions" from him. Dr. Andres Virchis, a consultant who treated Litvinenko at Barnet, told the inquiry Monday that there was no equipment there to detect alpha radiation.
As physicians investigated the collapse of Litvinenko's bone marrow, Nathwani said, "we were fishing for diagnoses." But, he said, organ systems failed one after the other, because "polonium from the gut was being transferred to various parts of the body."
Asked by a lawyer for the inquiry, Robin Tam, if it was true "that there wasn't in fact any treatment possible that could have saved" Litvinenko, Nathwani replied: "Correct."