An army corporal accused with others of "systematic abuse" of Iraqi civilians yesterday became the first British serviceman to admit a war crime.

Cpl Donald Payne, of 2 Bn, the Duke of Lancaster's Regiment, admitted the inhuman treatment of unnamed Iraqi civilians in Basra in September 2003, an offence under the International Criminal Court Act 2001.

He will be sentenced later and could face 30 years.

Payne, serving with the regimental police, denied a separate charge of unlawfully killing Baha Musa, 26, who died from multiple injuries while detained by troops from 1 Bn, the Queen's Lancashire Regiment. He also denies attempting to pervert the course of justice by telling those who saw him beating Mr Musa not to speak about it to investigators.

Julian Bevan, QC, for the Crown, said the case centred on the treatment of civilians held in temporary detention, pending a decision on whether they should be interned as a threat to coalition forces.

He alleged that the civilians were "repeatedly beaten by being kicked and punched". They were handcuffed and hooded, made to maintain a stress position for unacceptable lengths of time, deprived of sleep, continually shouted at and generally abused, in temperatures well over 100F.

Mr Bevan said that, despite his admission of inhuman treatment, Payne's "behaviour went some way beyond what he admits". The prosecutor said: "Before he [Mr Musa] died, he had removed his handcuffs, and it was believed by Cpl Payne that he was trying to escape.

"Certain measures were taken by Cpl Payne."

Mr Bevan was opening the case against Payne and six other servicemen. Apart from Payne's guilty plea to one charge, all the defendants denied all the charges put to them at the court martial at Bulford, Wilts.

L/Cpl Wayne Crowcroft, 22, and Kingsman Darren Fallon, 23, are also charged with the war crime of inhuman treatment. Sgt Kelvin Stacey, 29, is accused of assaulting an Iraqi civilian, causing him actual bodily harm. As an alternative, he faces a charge of common assault.

Mr Bevan stressed that the charges did not involve "robust or simply rough handling", which was bound to happen in a war zone.

"We are dealing with systematic abuse against prisoners involving, the Crown say, unacceptable violence against persons who were hooded, cuffed and wholly unable to protect themselves over a very long period."

It was the Crown's case, he continued, that what happened to these Iraqi civilians should never have been allowed to happen and was made possibly only by the negligence of three people.

They were the remaining defendants. Major Michael Peebles, 35, of the Intelligence Corps, who was Battle Group Internment Review Officer, and WO2 Mark Davies, 37, of the Intelligence Corps, the tactical questioner, are accused of negligently performing their duties by failing to take such steps as were reasonable to ensure that military personnel under their effective control did not ill-treat civilians detained for tactical questioning.

Col Jorge Mendonca, 42, the former Commanding Officer of 1 Bn, The Queen's Lancashire Regiment, is accused of negligently performing his duty by failing to take such steps as were reasonable to ensure that civilians held at the temporary holding centre under his command were not ill-treated.

In his opening address, Mr Bevan said: "Inhuman treatment of Iraqi civilians, albeit suspected of insurgency, sends utterly the wrong message to the very people whose trust and respect the coalition force needed."

The trial continues.