(Illustration from the Sherlock Holmes Museum, London)
Someone I know, who has a family history of law enforcement (a descendant of county sheriffs and police chiefs) explained to me that it is possible to figure out whether Vladimir Putin is responsible for the radiation poisoning of Alexander Litvinenko. It is a matter of deduction of the Sherlock Holmes kind in the story "Silver Blaze."
It is a matter of the dog-that-didn't-bark-in-the-night.
Since in principle official KGB (now FSB) killings are never solved, whether or not this particular case is solved will provide the answer.
If someone is arrested, tried, and convicted in Britain for poisoning Litvinenko, then Putin probably is innocent of the crime.
But if this crime remains forever unsolved, then, as Sherlock Holmes might have said: "Elementary, my dear Watson..."
You can read more about the case in today's Sunday Times (of London).