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Why did Russia kill Navalny with a lethal frog toxin? Chemical weapons expert Marc-Michael Blum believes the Kremlin never intended to get caught.

Source: Meduza

Two years after Alexey Navalny died in a Russian prison, five European countries confirmed through independent testing that he was poisoned. Analyses of Navalny’s biological samples, conducted by multiple independent laboratories, revealed traces of epibatidine — a deadly neurotoxin derived from a South American frog species and now produced synthetically. Why would Russia use an exotic poison to assassinate an imprisoned opposition leader? Where did the Kremlin get the toxin? And will Moscow face any consequences for potentially violating international weapons conventions? For answers to these and other questions, Meduza spoke with biochemist and chemical weapons expert Marc-Michael Blum, former head of the OPCW laboratory. 

The manner of Navalny’s death in prison was consistent with epibatidine poisoning, but few experts would have guessed that this exotic toxin was used to kill him, says Dr. Marc-Michael Blum. 

A biochemist by training, Blum worked at the Organization for the Prohibition of Chemical Weapons (OPCW) laboratory from 2012 to 2019. In 2018, he led the organization’s mission to Salisbury following the assassination attempt on former Russian spy Sergey Skripal and his daughter, Yulia. 

The way Blum sees it, the poison that killed Navalny leaves no doubt that he was assassinated. “If you are in a prison camp in northern Russia, there are no frogs from South American jungles. So clearly, there’s not even a chance that this could have been, say, accidental exposure,” Blum told Meduza. “In my opinion, that makes it very clear that somebody murdered him,” he added.

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Found in a South American frog species, epibatidine is now synthesized in laboratories — including Russia’s State Research Institute for Organic Chemistry and Technology (GosNIIOKhT). Although scientists once hoped to develop it into a painkiller, the substance proved too toxic for medical use. 

Like Novichok, the nerve agent used to poison Navalny in 2020, epibatidine disrupts the body’s nervous system, leading to paralysis, spasms, and respiratory failure. “Even though the toxic mechanisms are different, they work on the same thing: nerve conduction. So the symptoms would be the same or very similar,” Blum explains. “In the end, because of paralysis, you die of respiratory failure. You cannot breathe anymore.” 

Blum notes that epibatidine is difficult and costly to synthesize, which makes it an unsuitable chemical warfare agent for military operations. But targeted assassinations are a different story. “If you only need 10 milligrams, who cares about the cost?” he asks. 

What motivated the Russian authorities to use epibatidine remains unclear. Because epibatidine doesn’t break down in the body, it is easier to detect than other toxins, Blum points out. However, he doubts the choice of poison was meant to send a message — in part because Russian authorities initially refused to hand over Navalny’s body to his family. “I think the plan was that no samples would ever be analyzed,” Blum says. 

A similar theory surfaced after Navalny survived the Novichok poisoning in 2020, but Blum was skeptical then as well. “I always said he was supposed to die on that airplane,” he recalls. “It’s different from some other cases, like Litvinenko with the polonium,” Blum adds. “That was probably a message to the Russian diaspora in the United Kingdom: ‘We will get you. You cannot run away from us here.’”

The five European countries that confirmed the poison used to kill Navalny — the U.K., Sweden, France, Germany, and the Netherlands — accused Moscow of violating both the Chemical Weapons Convention and the Biological and Toxin Weapons Convention. Russia formally denied the allegations in a note to the OPCW Technical Secretariat. At the same time, Moscow’s permanent representative to the organization, Vladimir Tarabrin, argued that epibatidine falls outside the chemical weapons watchdog’s mandate. 

Unlike Novichok, which the Soviet Union developed as a chemical weapon, epibatidine is not on the OPCW’s Control List. However, as Blum explains, the Chemical Weapons Convention has a general-purpose criterion for such cases. “Any kind of toxic chemical can fall under the Chemical Weapons Convention,” Blum says. 

Epibatidine ultimately falls under both conventions, qualifying as both a toxin and a chemical. However, Blum considers the Biological and Toxin Weapons Convention “weaker” because it lacks an implementing body

While experts disagree over whether the Chemical Weapons Convention is the right “tool” for prosecuting a state-sponsored assassination, Blum argues that this isn’t the only allegation Russia faces. “The accusation is that they still have an ongoing chemical weapons program,” he explains. “Under the Chemical Weapons Convention, developing these weapons — not only producing and using them but developing them — is illegal.”

Shedding light on the poisons used against Navalny sends an important message, Blum says. Yet he doubts that Russia will face any real political consequences. In his view, Kremlin officials “just don’t care” about the legal and reputational risks that come with poisoning political opponents and violating international treaties. Russia’s State Research Institute for Organic Chemistry and Technology, which synthesizes epibatidine, is already subject to international sanctions with apparently little deterrent effect. 

“In the end, there will be some diplomatic ping-pong — accusation, counter-accusation — and most likely, that will be it,” Blum predicts. 

Nevertheless, he finds meaning in the confirmation of Navalny’s assassination. “He didn’t just die in a prison camp because of bad health or something. He was murdered,” Blum says. “The message is out there, and even though that’s very little, at least it’s something.”