Jumping the chain of command is never a good idea. At least send your boss an email (and BCC your gmail) to prove that you tried to go through official channels.
“I consulted an attorney, which is my right,” he said. “I had concerns about what I had seen at work, and this was just how it ended up playing out.”
Now because of due process (there's no actual evidence that his boss wouldn't have actually done the right thing, the employee just assumed) the boss will still have her job and be in position to act contrary to the interests of justice in the future.
And at this point his management has a reason to remove him from the job. Maybe he can fight it as a wrongful termination, but for now he's out of a job. I hope he gets his job back, but saying that your boss is corrupt is reason enough to give your boss enough rope to hang themselves IMHO.
A specious argument. If someone raised concerns that were then ignored, or had had past experience of that kind, it would be entirely appropriate to consult an attorney. On the other hand, the notion that it would have been held against him as an employee of the state is (I think, IANAL) BS. Raising the issue with his supervisors would have made it their problem; it's attorneys who bear the responsibility for discovery compliance, not the lab staff who do the actual forensic work.
Exposing your dangerous intentions to report potentially illegal behavior too early could mean inadequate time to prepare for repercussions.