Geoffrey Robertson: Mistakes the Mladic trial needs to avoid

The capture of Ratko Mladic is a signal moment in the delivery of the Nuremberg legacy that political and military leaders must eventually pay for their crimes against humanity.

He could – and should – have been taken into custody between 1996 and his disappearance in 2002, but diplomats then did not trust international justice: "The capture of Karadzic and Mladic," said a Nato spokesman, "is not worth the blood of one Nato soldier". Today, with Karadzic on trial, General Gotovina (Croatia's fugitive general) convicted, the verdict on Charles Taylor imminent and Colonel Gaddafi under indictment, there is more confidence that Nemesis will strike those who mass murder their own – and other – people.

While the Mladic trial will be an opportunity to see justice done, it must be seen to be done rather better than it was in the case of Slobodan Milosevic, who died before he could present any defence to a prosecution case that had lasted an intolerable three years. The expense and delay in The Hague contrasts starkly with justice at Nuremberg, where a convincing verdict on 23 Nazi leaders was rendered within 12 months. There are greater obligations now to disclose evidence and afford time, facilities and appeal-rights for defendants, but there is a problem with prosecutors and judges who think they have a duty to write history rather than to adjudicate specific allegations. They seriously overload their indictments – Milosevic, for example, was charged with responsibility for three separate wars spanning 10 years, when he could have been convicted simply and expeditiously for the ethnic cleansing of Kosovo.

The Mladic indictment charges genocide (difficult to prove and open to endless technical legal arguments) and numerous war crimes throughout the Balkan conflict. It should be replaced by just one charge, the crime against humanity constituted by his command responsibility for ordering the worst war crime since the Japanese death marches of POWs at the end of the Second World War, namely the slaughter of more than 7,000 prisoners of war – the Muslim men and boys killed at Srebrenica.

Limiting the trial in this way will enable some justice to be done before the inevitable claims of illness, old age and unfitness to stand trial. These are already being voiced by his lawyers in Belgrade, but the EU must insist that they be decided only in The Hague, after independent and carefully scrutinised medical examination. We have had too many international criminals escape justice for bogus medical reasons – remember Pinochet waving his stick happily after he landed in Chile, courtesy of Jack Straw's mistaken assessment that he was unfit to stand trial? Remember the convenient escape several years ago of Megrahi, the Lockerbie bomber, when a credulous Scottish justice minister was led to believe by doctors that he would die within three months?

Focus on this war crime will discomfort those who might have prevented it – especially the UN which refused to authorise the air strikes that would have stopped Mladic's advance, and the Dutch government which insisted on vetoing them to protect its cowardly battalion which was meant to be protecting the town but which immediately surrendered to Mladic and handed over to him the thousands of Muslims who had sought refuge in the UN compound. The moral nadir of UN/Nato "peacekeeping" where there is no peace to keep is the photograph of Mladic blowing his cigar smoke in the face of the spineless Dutch colonel while in the background those his battalion should have protected were taken off to the killing fields.

Nothing should detract from Mladic's command responsibility and he must not be indulged by a court which bent over backwards to help Milosevic at a time when international justice was under attack – especially from the Bush regime, which in a fit of puerility approved the "Bomb The Hague" Bill allowing the US president to use force to free any American under indictment there. If Mladic insists on defending himself, and then seeks to disrupt proceedings, he should have a capable team of lawyers imposed upon him, whether he likes it or not.

As to Serbia, it has some more atoning to do before EU membership can be assured. Karl Jaspers pointed out that the German people did not bear collective criminal guilt for Hitler, but they did bear collective political responsibility. So it remains the Serbian government's duty not only to send Mladic quickly to The Hague but to investigate and prosecute those who have harboured him. It has a particular duty, wrongly dodged by Hague prosecutors, to clean out the Serb orthodox church, whose priests blessed the death squads at Srebrenica. Without their blessing, I believe that some soldiers would have disobeyed their orders to shoot defenceless, hog-tied, men and boys. It is widely known that the church has harboured Hague fugitives in its monasteries and has been deeply implicit with the murderous aspects of Serb nationalism.

Some of Mladic's victims are upset that he has been free for 16 years, but his life on the run has been increasingly miserable. They should be grateful that the Serb police captured him alive instead of executing him summarily as the US did with Bin Laden. He will now appear as a reduced and demystified figure in The Hague dock – an inhumane serial killer rather than a hero. They should remember and take heart from the fact that the wheels of international justice grind slowly but they grind exceedingly small.

Geoffrey Robertson QC is author of 'Crimes against Humanity: The Struggle for Global Justice' (Penguin) and a former UN war crimes judge