SEATTLE: A key suspect in the US Army prosecution of soldiers accused of terrorizing unarmed Afghan civilians has agreed to plead guilty to murder charges next week and testify against his co-defendants, his lawyer said on Thursday.

Army Specialist Jeremy Morlock has signed documents stating his intention to plead guilty to three counts of premeditated murder and several other offenses when summoned on March 3 for court-martial at Joint Base Lewis-McChord near Tacoma, Washington.

The deal with prosecutors, subject to the approval of a military judge, calls for Morlock, 22, from Wasilla, Alaska, to serve no more than 24 years in prison, as opposed to the life term he faced if convicted of all charges in a trial.

He agreed in return to testify if called as a witness against other Stryker Brigade soldiers charged in connection with what has become the most serious prosecution of alleged atrocities by the US military in Afghanistan since the war there began in late 2001.

One of Morlock’s civilian defense attorneys, Geoffrey Nathan, said the plea agreement took five months to negotiate.

It could prove a linchpin in the military’s case against his remaining co-defendants.

Morlock is one of five soldiers charged with murder for the deaths of three Afghan villagers whose slayings were allegedly staged to look like legitimate combat casualties.

Prosecutors have described him as the right-hand man to the accused ringleader of the rogue platoon, Staff Sergeant Calvin Gibbs. They alone are charged with all three killings.

Several men, Gibbs and Morlock among them, are accused of collecting fingers from Afghan corpses as war trophies. But dozens of war-related photos seized as evidence, some said to show soldiers posed with Afghan corpses, remain the most potentially explosive element of the case.

The existence of such photos has drawn comparisons with pictures of Iraqi prisoners taken by US military personnel at the Abu Ghraib prison in Iraq in 2004. The Army has kept the Stryker Brigade photos sealed.

Four men charged with lesser offenses in the investigation already have pleaded guilty and been sentenced.

In addition to three counts of murder, Morlock has agreed to plead guilty to conspiring to commit murder, conspiring to assault a fellow soldier, trying to impede an investigation and using hashish.