The U.S. Army said Wednesday it will seek the death penalty against the soldier accused of killing 16 Afghan villagers in a predawn rampage in March.
The attack drew such angry protests that the U.S. temporarily halted combat operations in Afghanistan.
Staff Sgt. Robert Bales, 39, faces premeditated murder and other charges in the attack on two villages in southern Afghanistan.
Bales' civilian attorney, John Henry Browne, called the decision to seek the death penalty against his client "totally irresponsible."
Browne said the Army is simply trying to take the focus off its own failings in sending soldiers into war zones when they have already done multiple deployments and suffered from post-traumatic stress disorder.
Browne told The Associated Press that nothing would be served by executing Bales, who was serving his fourth deployment
Prosecutors said Bales left his remote base early on March 11, attacked one village, returned to his base and then slipped away again to attack another compound. Of the 16 people killed, nine were children.
No date has been set for his court martial, which will be held at Joint Base Lewis-McChord in Washington state.
Bales' wife, Kari Bales, said in a statement released Wednesday that she hopes her husband receives an impartial trial.
"I no longer know if a fair trial for Bob is possible, but it very much is my hope, and I will have faith," she said.
Bales' defence team has said the government's case is incomplete.
Outside experts have said a key issue will be to determine if Bales suffered from post-traumatic stress disorder. Bales served tours of duty in Iraq and Afghanistan.
During last month's preliminary hearing, prosecutors built a strong eyewitness case against the veteran soldier, with troops recounting how they saw Bales return to the base alone, covered in blood.
Afghan witnesses questioned via a video link described the horror of that night. A teenage boy recalled how the gunman kept firing as youth scrambled, yelling: "We are children! We are children!" A girl recalled hiding behind her father as he was shot to death.
An Army criminal investigations command special agent testified 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.
Several soldiers testified 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."