© Photograph: PAA still from video of a British soldier screaming abuse at hooded Iraqi detainees played to the public inquiry into the death of of Baha Mousa.
Britain will face fresh charges of breaching international law over the alleged torture and killing of prisoners during the war in Iraq, which began almost exactly 10 years ago. The allegations will be unveiled in the high court, when Britain will stand accused of a "systemic" policy of abuse committed over five years, from 2003 to 2008.

At a hearing scheduled over three days from 29 January, lawyers for 180 Iraqis who claim they are victims of abuse, or that their family members were unlawfully killed, will place a file of statements before two judges presiding over the court in London accusing British soldiers and intelligence officers of unlawful interrogation practices. These include hooding and the use of "stress positions", sexual abuse, beating and religious abuse of illegally detained prisoners. In some cases, the testimonies allege, the torture led to the death of the prisoner.

The statements were compiled during meetings with victims and relatives, mostly in Lebanon, by human rights lawyer Phil Shiner of the Public Interest Lawyers group, based in Birmingham.

The court will rule on whether the abuses were isolated incidents of which commanders, senior ministry officials and politicians were unaware, as the government insists, or "systemic" and authorised as policy. The MoD contends that any general problems of detention and interrogation were dealt with by an inquiry into the death of Baha Mousa, an innocent hotel worker killed while in British custody in Basra in 2003, and continuing internal investigations by its own Iraq Historic Allegations Team.

But the author of a book on the killing of Baha Mousa, Andrew Williams - a law professor at the University of Warwick - says what happened to Baha Mousa "may have shone a torch into a dark corner", but what is before the court next week is more like "a stadium in which we will switch on the floodlights".

His counsel team, led by Michael Fordham QC, will present five so-called "state practices" they claim were "unlawful, right to the top", including illegal interrogation techniques taught at the army intelligence facility at Chicksands, north of London, unlawful detention and unlawful use of lethal force.

Shiner's files are deeply shocking. Insults to Islam and sexual depravity feature frequently in the statements: a soldier is alleged to have masturbated over a prisoner, another to have committed sodomy with his finger; female interrogators are claimed to have stripped and feigned seduction in exchange for "information".

Most of the alleged incidents took place while prisoners were in custody, though some occurred during "strike operations" on people's homes, with suspects and their families allegedly subjected to abuse and crude violence. Prisoners who died in custody were invariably said to have done so due to "natural causes", despite beatings and kickings.

The hearing comes just weeks away from the 10th anniversary of the Iraq invasion, and will be counted as a measure of how far Britain can reckon with its own legacy in Iraq. South African archbishop emeritus Desmond Tutu last year urged in this newspaper that the then prime minister Tony Blair and others should be prosecuted by the international criminal court over the legality and conduct of the invasion.

"This is the crucial moment of decision", says Williams. "This is our last chance to get to the truth of what happened. This is what we demand of others, but we do not demand it of ourselves. What kind of message does that give the world about who we are?"