WASHINGTON -- The poisoning of Alexander Litvinenko, renegade Russian spy and fierce critic of Vladimir Putin's government, is everywhere being called a mystery. There is dark speculation about unnamed ``rogue elements'' either in the Russian secret services or among ultra-nationalists acting independently of the government. There are whispers about the indeterminacy of things in the shadowy netherworld of Russian exile politics, crime and espionage.

Well, you can believe in indeterminacy. Or you can believe the testimony delivered on the only reliable lie detector ever invented -- the deathbed -- by the victim himself. Litvinenko directly accused Putin of killing him.

Litvinenko knew more about his circumstances than anyone else. And on their deathbed, people don't lie. As Machiavelli said on his (some attribute this to Voltaire), after thrice refusing the entreaties of a priest to repent his sins and renounce Satan, ``At a time like this, Father, one tries not to make new enemies.''

In science, there is a principle called Occam's razor. When presented with competing theories for explaining a natural phenomenon, one adopts the least elaborate. Nature prefers simplicity. Scientists do not indulge in grassy-knoll theories. You don't need a convoluted device to explain Litvinenko's demise.

Do you think Anna Politkovskaya, the journalist who was investigating the war in Chechnya, was shot dead in her elevator by rogue elements? What about Viktor Yushchenko, the presidential candidate in Ukraine and eventual winner, poisoned with dioxin during the campaign, leaving him alive but disfigured? Ultra-nationalist Russians?

Opponents of Putin have been falling like flies. Some jailed, some exiled, some killed. True, Litvinenko's murder will never be traced directly to Putin, no matter how dogged the British police investigation. State-sponsored assassinations are almost never traceable to the source. Too many cutouts. Too many layers of protection between the don and the hitman.

Moreover, Russia has a long and distinguished history of state-sponsored assassination of which the ice-pick murder of Trotsky was but the most notorious. Does anyone believe that Pope John Paul II, then shaking the foundations of the Soviet empire, was shot by a crazed Turk acting on behalf of only Bulgaria?

If we were not mourning a brave man who has just died a horrible death, one would almost have to admire the Russians, not just for audacity, but for technique in Litvinenko's polonium-210 murder. Assassination by poisoning evokes the great classical era of raison d'etat rubouts by the Borgias and the Medicis. But the futurist twist of (to quote Peter D. Zimmerman in The Wall Street Journal) the first reported radiological assassination in history adds an element of the baroque of which a world-class thug outfit such as the KGB (now given new initials) should be proud.

Some say that the Litvinenko murder was so obvious, so bold, so messy -- five airplanes contaminated, 30,000 people alerted, dozens of places in London radioactive -- that it could not have possibly been the KGB.

But that's the beauty of it. Do it obvious, do it brazen, and count on those too-clever-by-half Westerners to find that exonerating. As the president of the Central Anarchist Council (in G.K. Chesterton's ``The Man Who Was Thursday'') advised: ``You want a safe disguise, do you? ... A dress in which no one would ever look for a bomb? Why, then, dress up as an anarchist, you fool!''

The other reason for making it obvious and brazen is to send a message. This is a warning to all the future Litvinenkos of what awaits them if they continue to go after the Russian government. They'll get you even in London where there is the rule of law. And they'll get you even if it makes negative headlines for a month.

Some people say that the KGB would not have gone to such great lengths to get so small a fry as Litvinenko. Well, he might have been a small fry but his investigations were not. He was looking into the Kremlin roots of Politkovskaya's shooting. And Litvinenko claimed that the Russian government itself blew up apartment buildings in Moscow in 1999, killing hundreds of innocent civilians, in order to blame it on the Chechens and provoke the second Chechen war. Pretty damning stuff.

But even Litvinenko's personal smallness serves the KGB's purposes precisely. If they go to such lengths and such messiness and such risk to kill someone as small as Litvinenko, then no critic of the Putin dictatorship is safe. It is the ultimate in deterrence.

The prosecution rests. We await definitive confirmation in Putin's memoirs. Working title: ``If I Did It.''