I would call an employment law attorney. The hardest part about proving a slander case is proving actual damages. However, there are many states where slander related to a person's professional aptitude have built-in or presumed damages. The last time I checked, Colorado is one of those states.
These claims are difficult and costly to pursue, but not impossible. Also, I would have the attorney rule out any hostile workplace claims.
What do you think a jury would give you if you could prove that this person called you a "troublemaker"? They are not exactly calling you a child molester. It is unlikely that characterization would go very far in court, if anywhere at all for just that. If HR is making these comments, then you can usually file a grievance if you have a union, or move up the ladder of HR, and get that HR representative in trouble. There is always a superior to somebody in HR, so move up the chain.
licensed attorney in Montana. Your specific state laws may be different.
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