An appeals court has upheld the conviction and life sentence of former Army Staff Sgt. Robert Bales for the slayings of 16 Afghan civilians and the wounding of six others in solitary pre-dawn raids on two villages in 2012.

The U.S. Army Court of Criminal Appeals, at Fort Belvoir, Virginia, rejected Bales' appeal Wednesday.

Bales, an Ohio native recently stationed in Washington state, pleaded guilty in 2013 to avoid the death penalty. In his appeal, he argued the Army withheld information about a witness in the case as well as evidence he may have been prescribed a psychosis-inducing malaria drug. The three-judge panel rejected those arguments as unfounded.

The massacre was one of the worst atrocities of the Afghanistan war. Angry demonstrations prompted the U.S. to temporarily cease combat operations.