California ? A former Marine sergeant facing the first federal civilian prosecution of a military member accused of a war crime says there is much more at stake than his claim of innocence on charges that he killed unarmed detainees in Fallujah, Iraq.

In the view of Jose Luis Nazario Jr., U.S. troops may begin to question whether they will be prosecuted by civilians for doing what their military superiors taught them to do in battle.

Nazario is the first military service member who has completed his duty to be brought to trial under a law that allows the government to prosecute defense contractors, military dependents and those no longer in the military who commit crimes outside the United States.

If Nazario, 28, is convicted of voluntary manslaughter, some predict damaging consequences on the battlefield.

“This boils down to one thing in my mind: Are we going to allow civilian juries to Monday-morning-quarterback military decisions?” said Nazario’s attorney, Kevin McDermott.