Hansen compared the military's conundrum to small states that have a death-penalty law on the books, but never use it.
"You don't have a lot of experience or institutional knowledge," said Hansen, who compared it to "the reinventing of the wheel every time one is done."
If Hasan is convicted and sentenced to death, his case will automatically go before appeals courts for the Army and the armed forces. If those courts affirm the sentence, he could ask the Supreme Court for a review or file motions in federal civilian courts.
The president, as the military commander in chief, must sign off on a death sentence.
"If history is any guide, it's going to be a long, long, long time," Hansen said.