Islamic State terrorists should be brought to justice via a system of public trials modelled on those used to convict Nazi leaders at Nuremberg in the immedate aftermath of World War II, according to a lead UN investigator.

That way the Islamic jihadists’ victims could be heard and the terrorist ideology “debunked” in an open, public forum.

British lawyer Karim Khan has made the call after journeying around Iraq with a team of almost 80 people to gather evidence and witness testimony for the UN body known as UNITAD.

“It’s a mountain to climb”, the human rights specialist told French newsagency AFP, as the investigative team works to analyse up to 12,000 bodies from more than 200 mass graves, 600,000 videos of IS crimes and 15,000 pages from the group’s bureaucracy.

Islamic State “wasn’t some kind of guerilla warfare or a mobile rebel group… that’s one aspect that is unusual” for international justice, Khan told AFP from the ultra-secure UNITAD headquarters in Baghdad.

“There was no taboo” for IS, Khan said.

“Who could have thought in the 21st century we would see crucifixion or burning a human alive in a cage, slavery, sexual slavery, throwing people off buildings, beheadings”.

Now Islamic State terrorists have been driven from most of their boltholes, Khan says justice must be done – and seen to be done – because, “Iraq and humanity requires its Nuremberg moment”, he said.

As a of Nuremberg, “nobody could be taken seriously if they would espouse the principles of Mein Kampf (written by Adolf Hitler). In fact alarms bells in the public conscience would be aroused if anybody thought the principles of fascism were an alternative political philosophy”, he added.

Nuremberg also “separated the poison of fascism from the German people”, according to Khan.

“It was one of the principles of Nuremberg that there is no collective guilt”, but individuals held responsible, and condemned.

A fair trial for Islamic State terrorist, “can also contribute to separating the poison of IS from the Sunni community”, a minority group in Iraq where two thirds of the population is Shiite, Khan said.

UNITAD is working to establish if IS actions constitute crimes against humanity, war crimes or genocide, the most serious crimes in international law.

“You will see in the next two months that we are feeding into some prosecutions that are already taking place in some states,” he added.

UNITAD “will build our own cases also” that will permit states which like Germany have universal jurisdiction to deal with crimes regardless of where they were committed and the nationality of the perpetrators and victims.

One example for UNITAD can be found in Iraq where Islamic State terrorists have been regularly prosecuted in public trials.

Last month three French citizens there were found guilty of joining Islamic State, as Breitbart News reported, and a fourth Mustapha Merzoughi, 37, was sentenced to death by hanging, according to an AFP journalist at the court.

Captured in Syria by a U.S.-backed force fighting the jihadists, they are the first French terrorists to receive death sentences in Iraq, where they were transferred for trial.

The four sentenced to death are part of a group of 12 French terror suspects whose cases faced the Iraq justice system.

Iraq has taken custody of thousands of jihadists repatriated in recent months from neighbouring Syria, where they were caught by the U.S.-backed Syrian Democratic Forces during the battle to destroy the IS “caliphate”.

In 2015 one report by the French senate revealed 47 percent of all known jihadists in what was then Islamic State territory were French citizens, with national intelligence networks having to keep tabs on up to 3,000 individuals at any one time.

AFP contributed to this story