What are the chances that Hosni Mubarak will stand trial for crimes committed as president of Egypt?
We do not need to look very far — at least in geographical terms — for a precedent: at the end of last year, a court in Tel Aviv found Moshe Katsav guilty of rape when he was a minister in the Israeli government and further sexual offences while he was president.
But just as Katsav was not much of a president, that is not much of a precedent: Egypt is unlikely to become a pluralist democracy like Israel, where two judges on the court that convicted Katsav were women and the third, who presided, was a Christian Arab. And if Mubarak is to face trial, it would presumably be for using state power to crush his enemies.
While in office, heads of state normally have immunity from prosecution for acts done as part of their official duties. Under international law, this immunity extends to serving diplomats, foreign ministers and perhaps defence ministers. Without it, the conduct of international relations would be impossible. But individuals lose these "personal" immunities when they leave office.
International law also recognises so-called "functional" immunities for various state officials acting in the exercise of their functions. Since their actions are attributed to the state itself, the immunities continue after the individual retires.
But Micaela Frulli, writing in the Oxford Companion to International Criminal Justice, says: "It is almost universally shared that functional immunity from foreign jurisdiction cannot be invoked by those who allegedly committed one of the so-called core crimes: war crimes, crimes against humanity, acts of torture and genocide."
This principle was recognised by a majority of the law lords who dealt in 1998 and 1999 with the case of Augusto Pinochet. The former Chilean dictator failed to persuade the UK's highest court that he had immunity from extradition to Spain to face charges of torture and hostage-taking.
And the same principle is to be found in the treaties governing international criminal tribunals. Take, for example, the Special Court for Sierra Leone, a hybrid court set up by agreement between Sierra Leone and the United Nations and currently sitting at a borrowed courtroom in The Hague.
The court's statute says that "the official position of any accused persons, whether as head of state or government or as a responsible government official, shall not relieve such person of criminal responsibility nor mitigate punishment".