FORT HOOD, Texas (AP) — A military jury has sentenced Maj. Nidal Hasan to death for killing 13 people at Fort Hood in 2009.

Hasan has said the attack on unarmed soldiers was motivated by a desire to protect Muslim insurgents fighting in Iraq and Afghanistan.

Hasan could become the first American soldier executed in more than half a century. But because the military justice system requires a lengthy appeals process, years or even decades could pass before he is put to death.

The Army psychiatrist will “never be a martyr” and deserves to be executed despite his attempt to tie his attack on unarmed soldiers to religion, a prosecutor told jurors on Wednesday.

History was full of instances of death in the name of religion, but it would be “wrong and unsupportive” to tie Maj. Nidal Hasan’s actions to a wider cause, Col. Mike Mulligan told jurors in his final plea for a rare military death sentence.

“He will not now and he will never be a martyr. He is a criminal. He is a cold blooded murderer,” the lead prosecutor said. “This is not his gift to God. This is his debt to society. This is the cost of his murderous rampage.”

Hasan, an American-born Muslim, has tried through court documents and leaks to the media to justify the November 2009 shooting rampage as necessary to protect Islamic and Taliban leaders from U.S. troops in Afghanistan and Iraq.

Hasan was never allowed to make those arguments to jurors, who convicted him last week for the attack that also wounded 30 people at the Texas military base. Still, Mulligan decided to answer those claims during the trial’s penalty phase.

“It was a conscious decision to commit murder to serve his own needs, his own wants,” Mulligan said in his closing argument. “His attack by him was all about him. This is about his soul, for his soul he stole life from 13 others.”

A few minutes after Mulligan finished, Hasan said he would give no closing argument — passing on his final chance to address jurors before they began deliberating his fate.

Hasan’s choice marked a continuation of an absent defense strategy that he has used since his trial began three weeks ago.

The Army psychiatrist has been representing himself during his trial. But his behavior has only stoked suspicion that his ultimate goal was martyrdom, in the form of a death sentence that would allow him to fulfill what prosecutors have described as a “jihad duty” under his Islamic faith.

Hasan has done nothing to dissuade jurors from giving him a death sentence. Even when his standby lawyers pleaded in vain to argue on his behalf, he described them as “overzealous.”