It is true that, in the past, ex-leaders have usually been handed over for trial by the same politicians who overthrew them, not by the courts. Milosevic was sent to The Hague in 2001 by his enemies in the government of Serbia, in contravention of a court order issued against his extradition by the Yugoslavian constitutional court. However, the illegality of that transfer did not trouble Human Rights Watch at the time, which welcomed the appearance in the dock of a man whom, like Fujimori, it had already proclaimed to be guilty.

But there is nothing new about trials of former heads of state as such. Fujimori is the 24^th head of state to face criminal trial for acts of state since Charles I was executed in 1649, and there have also been numerous additional trials of heads of government. Yet in three centuries of trials of former political leaders, there has not been a single acquittal. In the grim words of Danton to a French exile who returned from England to help Louis XVI’s defence in 1792, “Can one save a king who is on trial? He is dead as soon as he appears in front of his judges.”

Erich Honecker and Slobodan Milosevic are the only ex-leaders to have escaped conviction —the former by being about to die, the latter by actually dying during his trial. This acquittal rate is due to the fact that the trials are organised by victorious regimes against defeated ones. The conviction of the old leader is an essential source of legitimacy for the new one. Just as the new international tribunals are run by the great powers to justify their doctrine of military and judicial interventionism against weak and third world states, so the original prosecutions against Fujimori in 2000 were not brought by the Peruvian police but by the then president himself, Alejandro Toledo.

Toledo forced his governments to file more than 60 charges against Fujimori, indicting him for everything from his resignation in 2000 to the purchase of tractors from China while in office. Yet Toledo is hardly a neutral figure. He led the opposition against Fujimori and he was still clinging on to power when Fujimori announced he would return to Peru to stand for election last year. Fujimori’s detention in Chile on the Peruvian warrant torpedoed that challenge.

Trials of ex-leaders are often used by a victorious regime to cover up its own crimes. The Americans phrased the prosecution of Saddam Hussein in such a way that the invasion of Kuwait in 1990 could be regarded as a crime but not the invasion of Iran in 1979. Although the latter cost a million lives, the Americans presumably did not want their support for Iraq then to be discussed in court. Fuj’s trial will now take place under the aegis of President Alan Garcia, whom Fujimori defeated in 1990. When Garcia was first president (1985-90), far more Maoist guerrillas were killed than under Fujimori, who in fact brought Peru’s dirty civil war to an end. But it is “El Chino” who will be prosecuted for human rights abuses, not Garcia. Fujimori is being accused of corruption as well, which was also more rampant under Garcia.

The guilt of the defendant is often pre-announced in such trials. In 1941 in France, Marshal Petain said publicly that the Third Republic prime ministers, Daladier and Blum, were guilty before their trial had started, and insisted that the court’s job was simply to dole out the appropriate sentences. Both Fujimori’s successor and predecessor as president have declared him guilty, as have the world’s main human rights organisations —Amnesty, Human Rights Watch and the Inter-American Commission on Human Rights —who are in fact his main accusers. They seem uninterested in the presumption of innocence, and the media generally do not question the accusations.

However inevitable their conviction, former leaders often seem to relish their day in court. Vidkun Quisling of Norway in 1945 and Monsignor Tiso of Slovakia in 1947 both spoke for two whole days at their trials. They were shot shortly thereafter. Ex-leaders often make pompous appeals to the world outside and say that history will be their judge —although when the Greek military leader, George Papadopoulos, tried this in 1975, the judge snapped back: “Do you think history is absent from this courtroom?” Alberto Fujimori has many supporters in Peru, and maybe he will adopt this strategy. If it succeeds, that really will be unprecedented.

John Laughland is a Guardian columnist