THE PRECISE circumstances of the death of Alexander Litvinenko, the Russian ex-spy-turned-dissident who died of radiation poisoning Nov. 23, are likely to remain a mystery for some time. But the tragedy and the reaction to it actually reveal a great deal about Vladimir Putin's Russia -- and the West.

Litvinenko fell ill after a meeting with a source in his investigation of the recent fatal shooting of Russian journalist Anna Politkovskaya, another strong critic of the Putin regime. He issued a deathbed statement naming Putin as his murderer. This does not, of course, constitute proof of Putin's involvement. But the fact that Litvinenko was poisoned with polonium, a highly radioactive substance that is virtually impossible to manufacture or obtain outside a sophisticated nuclear laboratory, points to a high-level plot.

Kremlin spokesmen have derided charges of their involvement as "nonsense," and Putin has personally denied any role in Litvinenko's death. Then again, one wouldn't expect him to issue a statement along the lines of "If I did it, here's how I would have had Litvinenko murdered."

After Politkovskaya's death, Putin commented that "this murder does much more harm to Russia and Chechnya than any of her publications." Besides branding Politkovskaya's work exposing human rights abuses as harmful to her country, this cynical comment was remarkable for another reason. Putin didn't say the Russian government doesn't kill its critics, only that it had no reason to kill Politovskaya. Now, Soviet foreign intelligence spokesman Sergei Ivanov has given a similar response to Litvinenko's death, saying, "Litvinenko is not the kind of person for whose sake we would spoil bilateral relations," and "it is absolutely not in our interests to be engaged in such activity."

Yet the murder could be a very effective way to send a message to other critics of Putin and the Russian security apparatus, particularly those who seek to expose the details of the regime's misdeeds: Lie low, or else. On the other hand, those responsible for the murder may well have decided that the risk to Russia's relations with the Western powers was very low. After all, it's unlikely that the Kremlin connection (if it exists) can ever be established definitively. And, particularly given the West's current dependence on Russia for energy , it's also unlikely that any Western governments would risk a new Cold War over this murder, at least in the absence of definitive evidence.

The most likely scenario is that Russia will remain a suspect in Litvinenko's death without ever being proved guilty. And that may also be the best-case scenario for the Putin regime , with the suspicion strong enough to intimidate opponents but not strong enough to hurt Russia's interests abroad.

Does that mean Putin did it? Not necessarily. But he certainly had the motive, and it's not clear how many people with no connection to the Kremlin had the opportunity.

It is also possible that Litvinenko's death was a hit by his former employer, the FSB (Russia's Federal Security Service, the revamped KGB), acting without Putin's direct knowledge. But that hardly exonerates the people at the top.

Not everyone blames the Russian government. On his Russian-politics blog, Sean Guillory complains of the Western media's excessive willingness to believe allegations of nefarious deeds by the Russian government, noting that such assumptions treat Russia as "some sort of abnormal society" while holding up the West as a standard of modern democracy. But while every Western government has serious faults, they do not include poisoning critics.

In 1990 on a trip to what was then the Soviet Union, I interviewed Russian economist and activist Tatiana Koryagina, who warned me that contact with her might place me in danger from the KGB because of her work exposing government abuses. I wasn't sure at the time whether to dismiss the warning as paranoia. Those were the final months of the old Soviet regime. Now, after a decade of movement toward modern democracy, Russia is once again a country where the line between paranoia and reality is often blurred, a country where the independent media and political parties are being slowly strangled. In such a situation, the suspicion that the Russian regime may be reverting to its old ways -- not only muzzling but murdering its critics -- is not that far-fetched.