Secretary of  Defense Robert Gates' decision to award Sgt. Rafael Peralta a Navy Cross instead of a Medal of Honor makes no sense.

Either Peralta grabbed a grenade to protect his fellow Marines or he did not.  If Peralta grabbed the grenade then he deserves  a Medal of Honor.  If he did not grab the grenade than there is no reason to award him a Navy Cross.

Peralta was born in Mexico and joined the Marines as soon as he received a green card.  He subsequently became a U.S. citizen while serving in the Marines.

On  November 15, 2004, while serving as part of Alpha Company, 1st Battalion, 3rd Marine Regiment during Operation Al Fajr in the insurgent stronghold of Fallujah, Peralta entered a building with 11 other Marines including Lance Corporal T.J. Kaemmerer, a Marine combat correspondent attached to Peralta’s Company.  

According to Kaemmerer's account, they had cleared most of the concrete house when they came to the last room with the door closed.  Peralta opened the door and then jumped out of the way after being hit by AK-47 fire to allow the other Marines to fire into the room. 

Peralta was lying on the floor wounded when a yellow colored grenade landed near him.  As the other Marines scrambled to get away from it, they saw his hand grab the grenade and pull it toward his body.

Col. Eric Berg III, an Army pathologist who autopsied Peralta's remains, said in the 2005 report that the head wound from what is believed to be a ricochet from an American rifle would have been "nearly instantly fatal. He could not have executed any meaningful motions."

I don't know upon what empirical research he based his opinion.   In order to make such a definitive statement there would need to be scientific research comparing observations of people after  having been shot in the same manner.  Without such research Berg's statement is only an opinion, not a fact.

Four other experts - Peralta's battalion surgeon, and two neurosurgeons and a neurologist who examined the autopsy reports - said Peralta could have knowingly reached for the grenade because the ricochet that hit him was traveling at "low velocity" and would not have immediately killed him.

I don't know upon what evidence they are basing the claim that the wound occurred before the grenade exploded.  The Marines withdrew after the grenade exploded because the back of the building was on fire.  Safe withdrawal would have meant that they would have continued to fire as they left and the bullet could have hit Peralta's head at that time.
 
The experts may not be giving sufficient consideration to the role of reflex actions in such situations. Many heroic acts in war are reflexive actions. 

If a grenade lands near you and you take time to think about what to do it will explode before you make a decision.  Peralta wouldn't have had to be fully conscious.  His eyes saw the grenade and he reflexively grabbed it. 
 
 By the time I left Vietnam, I had developed reflexes to noises that could be exploding shells.  If I heard something that might be an incoming round, my feet would start moving to the bunker while my brain determined if it was incoming or outgoing.   

If Peralta could not have grabbed the grenade, what action did he take that would justify a Navy Cross?  Opening the door to the room where the insurgents were might quality for a bronze star or maybe a silver star, but not a Navy Cross. Otherwise the Navy would have to award such a medal everytime someone entered a room where an enemy might be.

Marine Reserve Lt. Col. Scott Marconda, who investigated the incident in 2004 as a major and judge advocate, makes a good point. "there's no way that grenade got under the center of mass of his body without him putting it there. I'm not a cheerleader. It is what it is. And my point is: I believe that he did that."

Does the Department of Defense believe that the grenade just miraculously landed where Peralta's body could protect the other Marines from the blast?
 

Something is very wrong here.   Congress needs to investigate why the Department of Defense has made such a strange decision