Yet another opponent of Russian president Vladimir Putin lies in a Moscow hospital this week, recovering from strange symptoms that his wife believes to be an assassination attempt by poison.
It's the latest in a long line of suspected poisonings that Russian secret services are suspected of carrying out over the past few decades, a legacy that stretches back to the 19th century, experts say.
Vladimir Kara-Murza, 35, fell ill last week during a tour of Russia to promote a film about the life and death of opposition leader Boris Nemtsov in 2015. Kara-Murza had been poisoned once before in 2015, falling ill with a kidney ailment that required months of recovery.
Kara-Murza is in critical but stable condition after being put into an induced coma, according to news reports. His wife, who lives in Centreville, Va., said Tuesday that she believes his illness is the result of poisoning for his outspoken views against Russia's leader.
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Kara-Murza has been working for the Open Russia Foundation of Mikhail Khodorkovsky, a former oil tycoon who served a decade in jail after openly opposing President Vladimir Putin.
Why do Russian agents use poison against critics?
"It's a fear weapon in that it can strike silently," said Matthew Rojansky, an adjunct professor at the Johns Hopkins University School of Advanced International Studies, and the director of the Kennan Institute at the Woodrow Wilson International Center for Scholars. "If you shoot someone on a bridge in front of the Kremlin, it makes them a martyr. If you poison someone, and they don't even die and the illness recurs and who knows what the cause is, it's a little more plausibly deniable."
Kara-Murza is the latest Russian opposition figure to fall ill with strange symptoms.
In 2012, Russian businessman Alexander Perepilichny collapsed and died outside his London mansion, even though he was in good health . He had been given asylum in the UK after exposing Russian officials in a tax scam. A forensic investigation found traces of a Chinese poison flower in his stomach.
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In 2006, Andrei Litvinenko was killed with radioactive Polonium-210 put in his tea during a meeting with two Moscow agents, one of whom is now a member of the State Duma. A British judge's investigation found that Putin was likely responsible for the killing.
Ukrainian opposition leader Viktor Yushenko fell ill in 2004 during the so-called "Orange Revolution," breaking out in strange lumps on his face. It was later found to be dioxin, a highly toxic byproduct of industrial activity.
Figuring out what poison is responsible can be tricky, according to Bruce Goldberger, a forensic toxicologist at the University of Florida College of Medicine. "Most well-suited laboratories can conduct test for a wide range of drugs and other poisons," said Goldberger, who often consults in high-profile poisoning deaths. "But they have a difficult time assessing exposure to heavy metals as well as radioactive substances."
Kara-Murza's toxicology tests were sent to labs in Israel and France and results are pending. For most of these lethal poisons, there's not much that doctors and nurses can do except to support the patient in the hospital, and hope that the patient's internal organs, heart and cardiovascular system can handle the toxic onslaught.
As for the motive behind the Kremlin's latest poisoning, that will be take some time to figure out, Rojansky said.
"If they wanted him dead, he would be dead," he said. "So it is a bit of a mystery at this point."
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