The eight men are being held at Camp Pendleton Marine Corps base north of San Diego, Jeremiah Sullivan III, who represents one of the men, said on Thursday.
The men served in Iraq with the 3rd Battalion, 5th Marine Regiment, and are members of the battalion's Kilo Company. The highest-ranking serviceman is a staff sergeant.
Sullivan said he learned from Marine Corps attorneys that the charges have been drafted and official charging documents could be given to the defendants as early as Friday.
The Iraqi man was killed west of Baghdad on April 26. His death is unrelated to the shootings of as many as two dozen civilians in the western Iraqi city of Haditha. The Pentagon is investigating troops from the 3rd Battalion, 1st Marine Regiment in that case.