(CNN) -- In amended charges presented Friday, U.S. military authorities accused Army Staff Sgt. Robert Bales of illicit steroid and alcohol use in addition to 16 counts of premeditated murder for allegedly gunning down villagers in Afghanistan earlier this year.
Bales' lawyer, John Henry Browne, responded to the changes by saying he is "so relieved" that military prosecutors "came out publicly with the steroid use."
"Steroid use is going to be an issue in this case, especially where Sgt. Bales got steroids and how he got steroids," Browne told CNN.
The U.S. military said that, in March, Bales left his outpost in Afghanistan in the middle of the night and single-handedly attacked two villages. The incident further riled relations between Washington and Kabul, intensifying the debate about whether to pull American troops ahead of their planned 2014 withdrawal.
Bales was taken into military custody soon thereafter, and subsequently charged with 17 counts of murder and six counts of assault and attempted murder. He is being held in a military prison in Fort Leavenworth, Kansas.
The new slate of charges detailed Friday by the U.S. Army -- which are defined as violations of the Uniform Military Code of Justice -- include 16 counts of premeditated murder, one of several changes that the military said were done "to conform to developments in the ongoing investigation."
Bales still faces six counts of attempted murder, as well as seven counts of assault -- one more than previously.
In addition, the Army sergeant is charged with two counts "of wrongfully possessing and using a Schedule III controlled substance" -- which the military, in its release from Joint Base Lewis-McChord in Washington state where Bales is based, defines as steroids.
He is also charged with a single count of "wrongfully consuming alcohol while deployed."
Browne, Bales' lawyer, called that charge "just a red herring. You don't got out and commit the type of crimes (murders) he is accused of because you took two sips of alcohol off of someone else's Gatorade bottle."
CNN's Paul Vercammen contributed to this report.