To rephrase what I think he was asking: at best they failed to do their incredibly important job. At worst, they committed first degree murder as part of a criminal conspiracy. Unfortunately, due to their actions, we don't know what happened.

So, why is it that they are not sitting in jail for the minimum sentence on manslaughter, or at least sitting in jail til they cooperate enough to tell what actually happened.

If they don't know anything(somehow), they still fucked up an incredibly important job. Manslaughter sentence.

If they do know, make them a deal for cooperation or sentence them to first degree murder. Potential death penalty.