Chug,
I am intimately aware of how the course of justice gets perverted by the Mandarins up the chain.
With no effort at all I can list several very notable incidents that has happened.
Some of the examples would be the Pat Tillman Friendly Fire death, the USS Iowa Main Turret explosion, The Moscow Embassy Marine Guard investigation, and the Rickover investigation.
On the other hand I know of investigations that took on a life of its own despite repeated confirmations nothing worth investigation occurred.
Government bureaucracy everywhere do not like sunshine being shined on their mistakes thus it should come as no surprise to any of us that these events occur.