Britain says the circumstantial evidence points to Russian President Vladimir Putin's involvement in the poisoning death of an ex-Russian security agent who died after drinking polonium-laced tea at a London hotel.
So what's Britain going to do about it?
Not very much. And that's largely in keeping with the West's response to Putin's many controversial actions throughout his 16 years in power.
"We have a pretty difficult relationship with the Russians in any event," British Prime Minister David Cameron said. "But do we at some level have to go on having some sort of relationship with them because we need a solution to the Syria crisis? Yes, we do, but we do it with clear eyes and a very cold heart."
Alexander Litvinenko, the security agent who died back in 2006, is one of several high-profile critics of Putin who have been murdered or perished in mysterious circumstances during his tenure.
The reality is that most Western leaders tend to echo Cameron's statements, saying they feel the need to engage with Russia on a host of matters rather than opt for a head-on confrontation.
Putin, meanwhile, seems to thrive on criticism from the West. He uses it to boost his popularity at home and bolster his claim that the West is working to weaken Russia on multiple fronts that range from expanding NATO to sanctioning Russia's economy to shrinking Moscow's role on the international stage.
The Kremlin dismissed the British report, with spokesman Dmitry Peskov saying it could "only further poison the atmosphere of our bilateral relations."
Britain and Russia have strong financial ties, and many European states have extensive trade with Russia. The U.S. and Europe did impose sanctions after Russia's annexation of Ukraine's Crimea region in 2014, and those punitive measures have had some bite, especially when combined with the crashing oil prices that have plunged Russia's economy into recession.
Yet the Obama administration also cites the need for Russian cooperation. Moscow was seen as crucial to the nuclear deal that six world powers reached with Iran last July. As part of that deal, Iran recently shipped 98 percent of its enriched uranium to Russia.
Russia is also an important player in Syria, where it staunchly supports President Bashar Assad and has been waging airstrikes on his behalf. The West has been sharply critical of Russia's military role but acknowledges that Moscow has leverage with Assad. And while Russia and the West disagree on whether Assad should stay or go, they share an opposition to the Islamic State.
But critics challenge the notion that the West needs Russia as much as it seems to think it does. They argue that Putin has proved an unreliable partner time and again and the West has little to show for the times it has tried to work with him.
"Confrontation with Putin is inevitable as long as he stays in office," Garry Kasparov, the former world chess champion from Russia, and a fierce critic of Putin's, said in an interview Wednesday with Reuters.
Kasparov, who has a home in New York and now lives outside Russia, also said:
"We don't know what Putin will do when he gets desperate. He is in a very difficult situation. Oil, you know, is sliding down. If oil gets to 20 [dollars a barrel], Putin's Russia is bankrupt. Who knows what he will do? In the last few years, we could see his response to economic challenges was always the same — to create more tensions outside of Russia."
Putin and Litvinenko had a personal dispute dating to the 1990s, when Putin was the head of Russia's Federal Security Service, or FSB, where Litvinenko worked, according to the British report. The feud escalated when Litvinenko fled his homeland for asylum in Britain in 2000 with his wife and child. He worked with British intelligence and criticized Putin.
Litvinenko's widow, Marina, praised Thursday's report by a British judge and called for Britain to expel "all Russian intelligence operatives," though there was no indication Britain would take such a step.
Britain has issued arrest warrants for two Russian suspects, Andrei Lugovoi and Dmitry Kovtun, but they remain free in Russia. Britain said it would freeze the assets of the two men, though it was not clear what assets, if any, the two have in Britain.
Greg Myre is the international editor of NPR.org. Follow him @gregmyre1