(CNN) -- The Pentagon is fighting a push to award the Purple Heart to victims of the 2009 massacre at Fort Hood, Texas, fearing it could hurt the case against the Army officer charged with turning on his comrades.
"If you deal with the perpetrator of these crimes, he was a terrorist, essentially," one of the bill's co-sponsors, Texas Republican Rep. Bill Flores, told CNN affiliate KXXV. "We ought to treat these military men and women that were hurt like they were in a battlefield theater."
Maj. Nidal Hasan is awaiting a court-martial on charges that he gunned down 13 people and wounded 32 at Fort Hood, the country's largest Army post. Testimony is set to begin on July 1.
But in a position paper obtained by CNN, the Defense Department argues that awarding the Purple Heart to the Fort Hood victims would make it harder to convict Hasan in the death-penalty case and "deprive the victims of these crimes the right to see justice done."
"Defense counsel will argue that Major Hasan cannot receive a fair trial because a branch of government has indirectly declared that Major Hasan is a terrorist -- that he is criminally culpable," the document states. That could lead to a delay of the case or the reversal of a guilty verdict on appeal, it continued.
"This laudable sentiment mistakenly and unwillingly supplants the criminal trial process by infusing official, formal statutory conclusions about the motive, intent and culpability of the man charged with the crime," the memo reads.
Prosecutors aim to show that the Hasan, an American citizen of Palestinian descent, was a radical Islamist. Witnesses reported that Hasan opened fire with two pistols, yelling "Allahu akbar" -- Arabic for "God is great" -- as he shot troops preparing to deploy to Afghanistan.
Investigations have found that he had been communicating via e-mail with radical Yemeni-American cleric Anwar al-Awlaki, who was killed by a U.S. drone attack in 2011. Hasan had been scheduled to deploy to Afghanistan before the killings but had been telling his family since 2001 that he wanted to get out of the military.
The bill has the support of former House Speaker and GOP presidential hopeful Newt Gingrich, who dismissed the Defense Department's concerns about a fair trial in an interview on CNN's The Situation Room.
"Does anybody doubt he was in the room? Does anyone doubt he yelled 'Allahu akbar?' Does anyone doubt he shot all those people?" Gingrich asked. "We have a lawyer-driven system that is sick."
Gingrich said the military has "bent over backwards" to avoid declaring the killings an act of terrorism. By comparison, he said, German spies caught during World War II were tried and executed "in a matter of weeks."
"There is no question this man is guilty. None. Zero," he said.
Pentagon spokesman George Little declined to comment Monday, citing the pending case. But a congressional source, speaking on condition of anonymity because of the legal concerns, called the military's position "dead wrong."
"If they stand by this, they should ask for all the Pentagon's 9/11 award recipients to give their medals back," the source said. "They're not gonna do that, though."
The Pentagon document notes that victims of an international terrorist attack are eligible for the Purple Heart. But expanding that to include domestic crimes or terrorism, it asserts, "would be a dramatic departure from the traditional Purple Heart award criteria."
"Ultimately, such an unprecedented action would thwart the real and lasting measure that will bring closure to the grieving and harmed victims and families -- the trial itself," the position paper states.
However, the bill Flores co-sponsored states that the Senate Homeland Security and Governmental Affairs Committee branded the Fort Hood killings a "terrorist attack" in a 2011 report.
"It basically just says if you were shot at Fort Hood that day or you were shot in Afghanistan, you're treated exactly the same," Flores said.