Closing arguments began Tuesday before a military panel investigating the role a Marine special operations unit played in the fatal shooting of Afghan civilians in March.
The Court of Inquiry must also review about 5,000 pages of evidence related to the shootings. The court will recommend whether criminal charges be filed against two officers in charge of the unit.
It is not clear how long it may take the panel to reach a decision.
Several Marines have said a suicide car bomb began a well-planned ambush on their convoy March 4 along Highway 1 in Afghanistan's Nangahar Province. But an Afghan human rights organization said Marines fired indiscriminately at pedestrians and motorists.
The shootings killed as many as 19 Afghan civilians, according to an Army report, but no evidence has shown exactly how many were killed or wounded.
Major Phillip Sanchez, a government lawyer, said the unit was out to prove itself and ignored initial orders to only gather intelligence. Sanchez also accused Marines of lying during testimony about another incident.
Civilian lawyer Knox Nunnally said the Marines were treated unfairly. He also said Afghans who said they were wounded were told by village elders to lie to collect government payments.