I agree with the NC Times' conclusion, but not all their premises. Mendoza is a defense witness. I'm puzzled about the way the case was charged, but there's no evidence of immunity just for prosecution witnesses.
“I can’t understand how investigators could possibly separate the results of a fireteam’s actions into individual charges. We know Cpl. Mendoza shot the insurgent in the doorway. But how can LCpl. Tatum be charged, but not Cpl. Mendoza, for the other deaths in the first two houses?”....
There were two Iraqi men that no murder charges were preferred. One was associated with house #1, the other with house #2. I alwsys assumed the one from house #1 was the guy that was shot “running on the ridgeline”.
You ask how they can charge one and not another when they belong to the same fire team - Maybe the charges were distributed among various Marines in hopes of getting them to turn on each other. Also, we don’t know what kind of pressure is/was put on those who weren’t charged, but did kill Iraqis that day. Maybe the prosecution thought they could get at least one plea to build their case against everyone else. It worked in the Hamdania cases. One plea, and the dominoes started falling.