The mysterious death of Alexander Litvinenko throws a harsh spotlight on the Russian secret services. The controversy has engulfed Russian President Vladimir Putin, forcing him to publicly deny any involvement in the killing. That’s probably true: Mr. Putin loses far more than he gains from this incident. But he is responsible — either by design or by omission — for empowering the security services and creating an environment that blurred the lines between state and personal interests.

Mr. Litvinenko once worked for the FSB, a successor agency to the KGB, handling domestic security concerns in Russia. He first received public attention in 1999 when he claimed at a press conference that the FSB had ordered him to kill Mr. Boris Berezovsky, a high-profile Russian oligarch who had the temerity to challenge Mr. Putin by backing an opposition political party. (Mr. Berezovsky’s readiness to cross the president forced him into exile in London.)

Mr. Litvinenko later published a book in which he claimed the FSB had carried out apartment bombings in Moscow in 1999 so that Chechen terrorists would be blamed. The case has never been solved. (Shortly after those attacks, security officials were arrested with bomb-making materials in another apartment building; they claimed they were conducting a security test.)

Mr. Litvinenko was forced to flee Russia after being charged with treason and he received political asylum in Britain. Most recently, Mr. Litvinenko was looking into the death of Russian journalist Anna Politkovskaya, a fearless investigator of Russian government abuses in Chechnya who was murdered contract style in the doorway of her apartment building Oct. 7.

On Nov. 1, he spent an evening in London with two former Russian associates and later met an Italian journalist. Shortly afterward, he fell ill and checked into a hospital. British health officials determined that he had been poisoned with polonium 210, a radioactive isotope. On Nov. 23, he died, leaving a vitriolic last statement in which he blamed Mr. Putin for his death.

Since then, traces of the isotope have been detected at around a dozen sites in the London area — including Mr. Litvinenko’s home, the sushi bar where he met his former associates and Mr. Berezovsky’s office — and on at least two British Airways jetliners. Mr. Litvinenko’s wife and the Italian journalist have tested positive for small amounts of the radiation; neither was showing symptoms of poisoning over the weekend.

Mr. Litvinenko’s suffering — lurid photographs from his hospital bed, his hair gone, his face gaunt, were splashed across the front pages of British newspapers — apparently compelled Mr. Putin to make a statement at a meeting with European Union leaders in Helsinki. Mr. Putin expressed regret over the tragedy, but insisted that talk of Russian government involvement had “nothing to do with reality.”

The presence of polonium makes it hard to dismiss Mr. Litvinenko’s death as a mere accident. Mr. Litvinenko had been a nuisance with his allegations against the president. But he was only a nuisance and it would not take much to realize that an assassination attempt of this type would cause even more controversy.

But that does not mean that rogue elements of the security services, either in or out of the government, were not involved. One hallmark of Mr. Putin’s term in office has been the willingness to put former colleagues in positions of power throughout his administration. Mr. Litvinenko’s allegations were potentially dangerous if they exposed the readiness of political and business entities to blur the boundaries between state and private interests. The individuals who benefit from this situation could have taken action on their own.

There is another hypothesis. Some speculate that the real beneficiaries of Mr. Litvinenko’s death are those who want to see Mr. Putin put on the defensive. Chief among them is Mr. Berezovsky. According to this logic, the same forces killed Mr. Litvinenko and Ms. Politkovskaya — not because they were a threat to the Russian government but because their deaths would focus attention on the Russian authorities. This reasoning seems too clever: There are other ways to embarrass Mr. Putin that do not involve killing two individuals who were working for the same purpose as the instigators — and do not require hard-to-acquire radioactive substances.

The most important thing now is that the investigation into Mr. Litvinenko’s death be vigorous and uninhibited (the same applies to that of Ms. Politkovskaya). State interests cannot be used to block attempts to uncover the truth. Since the investigation is by the British authorities, there are reasons for hope.

The world should know whether there is state involvement in these murders. If none is apparent, then surely Mr. Putin will want to know who is going to such lengths to humiliate him.

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