The US Army said it will seek the death penalty against the soldier accused of massacring 16 Afghan villagers during pre-dawn raids in March.
The announcement followed a pretrial hearing last month for Staff Sgt Robert Bales, 39, who faces premeditated murder and other charges in the attack on two villages in southern Afghanistan.
Prosecutors said Bales left his remote base in southern Afghanistan early on March 11, attacked one village, returned to the base, and then slipped away again to attack another nearby compound. Sixteen people were killed, nine of them children.
No date has been set for his court martial, which will be held at Joint Base Lewis-McChord south of Seattle.
Bales' civilian lawyer, John Henry Browne, did not immediately return an email seeking comment. But on Tuesday, he said he met with Army officials last week to argue that Bales should not face the possibility of the death penalty, given that Bales was serving his fourth deployment in a war zone.
Bales' defence team has said the government's case is incomplete and outside experts have said a key issue going forward will be to determine whether Bales, who served tours of duty in Iraq and Afghanistan, suffered from post-traumatic stress disorder.
An Army criminal investigations command special agent testified earlier that Bales tested positive for steroids three days after the killings, and other soldiers testified that Bales had been drinking the evening of the massacre.
But prosecutors, in asking for a court-martial trial, have pointed to statements Bales made after he was apprehended, saying that they demonstrated "a clear memory of what he had done, and consciousness of wrong-doing."
Several soldiers testified at a hearing that Bales returned to the base alone just before dawn, covered in blood, and that he made incriminating statements such as, "I thought I was doing the right thing."
The killings drew such angry protests that the US temporarily halted combat operations in Afghanistan, and it was three weeks before American investigators could reach the crime scenes.