SEATTLE (AP) -

The lawyer for the American soldier who killed 16 Afghan civilians says Staff Sergeant Robert Bales used a controversial malarial drug linked to paranoia, hallucinations and psychosis while on a previous deployment in Iraq.

The Seattle Times reports that it's unclear whether Bales took the same drug in the days leading up to the slayings last year near a remote Army outpost in Afghanistan.

Bales' attorney, John Henry Browne, tells the Times that he has documents indicating his client took the drug while in Iraq but says medical records for his client's time in Afghanistan are incomplete.

Bales pleaded guilty to the killings last month. A jury will decide in August whether the soldier is sentenced to life with or without the possibility of parole.