Just to give an idea of what these defendants are facing, 3 Blackwater guards testified against them to a grand jury in 2010. Murphy was one of them.
http://www.nytimes.com/2010/01/17/world/middleeast/17blackwater.html
As I understand it, radio logs as well as photos of the Blackwater vehicles show that the convoy took hostile fire including from Iraqi police. There’s going to be a strong defense in this case.