The Wall Street Journal says a U.S. Army soldier could face capital punishment for killing 16 Afghan civilian men, women and children.

The U.S. daily quoted U.S. Defense Secretary Leon Panetta as saying on Monday that Staff Sergeant Robert Bales could face the death penalty.

The report said prosecutors haven't spoken publicly about the case but noted President Barack Obama has instructed the military to prosecute the case aggressively.”

Bales' lawyers are expected to focus their defense on mental-health problems that may have been out of the soldier's control.

The lawyers noted that Bales served three tours in Iraq, a tour in Afghanistan, and suffered a traumatic brain injury as well as a severe foot injury.