Hunting Nazis has always needed special skills: a command of international law, a precise sense of the logistics of the Holocaust, a nose for archival discovery and the readiness to wear down shoes in pursuit of a suspect.

This rare breed seems to be close to extinction.

Public interest is waning and funding is very limited. Simon Wiesenthal, the original Nazi-hunter, operated out of a cramped office in Vienna and conditions have, if anything, become more difficult as his successors struggle to convince a sceptical public that it is morally justified to pursue old criminals to the end of the world.

Two Second World War trials in a month, therefore, are important. The case of Heinrich Boere, now on trial in Aachen, will expose not only the activities of hit squads in occupied countries but also flush out some of the remarkable bureaucratic obstacles that were thrown up by the German judiciary over half a century to prevent him being put in the dock.

The post-war West German justice machine was often very protective of Nazis; indeed, many of the detectives signed up by the West German state had learned their craft in the Third Reich. It takes determination to break through decades of institutional indifference or outright hostility and bring a wartime murderer to justice. That is the measure of the achievement of Ulrich Maass, the prosecutor in the Boere case who is based at one of the few remaining investigative centres into Nazi-era crimes.

Outside Germany the most high profile Nazi hunter is Efraim Zuroff of the Simon Wiesenthal Centre, who has spent the past few years on Operation Last Chance, presenting dossiers on suspects to the governments of the Baltic States, the Balkans and elsewhere, urging action before the defendants are too infirm to be tried. His list of suspects is topped by Albert Heim, the “Doctor Death” of Mauthausen concentration camp, aged 95 if is still alive. Both Mr Boere and John Demjanjuk figure high on his list, too.

The Demjanjuk trial, to start in Munich on November 30, is critical. It will try to establish the guilt of a concentration camp guard who prodded Jews into gas chambers. Surviving witnesses are old and frail; some were children when the crimes were committed. How does that work within the modern judicial system? What rhetorical tools will the Demjanjuk defence use to demolish witness testimony? What if the evidence is insufficient for a conviction? What kind of signal would the freeing of Mr Demjanjuk send to those on the far Right who already argue that the Holocaust is a fiction? And, if there are convictions, sceptics ask, what will be achieved by putting two old men behind bars?

The last question is the easiest to answer. It is the pursuit of truth that counts, not the nature of the punishment.

It has never been more essential to explain to a wider public the mechanics of mass murder: how orders are given and interpreted, how a sense of duty can mutate into killing someone. There is also a powerful moral obligation to demonstrate that killers, in or out of uniform, should be held responsible for their actions. These are fundamental lessons.

Nazi hunters are not redundant. They are essential in stirring memory and in setting civilisation’s boundaries. That is why the trials are important — and why reporters must sit through them.

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