Nidal Hasan, who was shot in the chest by a police officer during the November 5 rampage at the sprawling Fort Hood military base in Texas, will likely never walk again and has no control over basic bodily functions.
It will likely be some time before he is ready to face trial, said John Galligan, Hasan's civilian attorney.
"He's permanently paralysed from the upper chest area down,'' Galligan told AFP.
"He still has significant collateral issues... he's an invalid.''
Galligan has asked the army to move Hasan to a hospital closer to his office near Fort Hood so that he can more easily meet with his client.
Hasan remains under guard at Brooke Army Medical Center in San Antonio, about 190 kilometres away from where the massacre took place.
The Pentagon has launched an elaborate investigation into the shootings to determine whether warning signs were missed and to prevent such an assault from happening again.
Hasan is being investigated for links to Islamic extremism, including his contacts with a radical cleric who blessed the killing spree.
He faces 13 counts of premeditated murder and 32 counts of attempted premeditated murder.
Twelve soldiers and one civilian were killed in the attack. Another 42 people were wounded.
Galligan said he was worried that his client would not be given a fair trial at Fort Hood given the publicity surrounding the case and the way prosecutors are "rushing things.''
"My job is to make sure that Major Hasan gets a fair, free day in court. That's what our service members fight for,'' Galligan said.
"When I defend Major Hasan, I feel like I'm defending every soldier in uniform. Too many Americans, from high level politicians on down to some people in my local community have forgotten the significance of that.''
Galligan said he was not given the opportunity to be present when investigators interviewed Hasan at the hospital or when he was formally charged and cannot get the company commander to return his phone calls.
Hasan is also facing unusually heavy restrictions in hospital, Galligan said. He is being monitored by a video camera, he has been told that all communication must be in English, his correspondence is being monitored and copied, his visitors are strictly limited and Galligan cannot be present at the same time as Hasan's family.
"I love the military justice system,'' Galligan said.
"If it's done right you can get a better trial, sometimes a fairer trial than you can in state court or federal court. If it gets derailed there is nothing worse than having the army coming against you.''