The U.S. Army psychiatrist on trial for killing 13 soldiers and wounding 31 others in 2009 at Foot Hood, Texas, has rested his defense without calling any witnesses.
Acting as his own defense attorney, Major Nidal Hasan chose not to challenge the government's case against him.
Military prosecutors on Tuesday had rested their case against Hasan, an American-born Muslim who has admitted in court to being the shooter.
The 42-year-old Hasan faces 13 counts of premeditated murder and 32 counts of premeditated attempted murder. He could face the death penalty if all 13 officers on the jury find him guilty.
Hasan has sat mostly silent during the trial. His court-appointed lawyers say he is trying to get a conviction and death sentence in an attempt at martyrdom.
In his opening statement, Hasan had told the court he had "switched sides" in the war on terror to wage a battle against U.S. soldiers he believed would attack Muslims in Iraq and Afghanistan.
The military judge set closing arguments for Thursday.