Here, at Constitution.org I found this:
FN8. Joe Sexton, Jurors Question Honesty of Police, N.Y. Times, Sept. 25, 1995, at B3 (quoting Michael F. Vecchione, Brooklyn District Attorney Charles J. Hynes’s deputy in charge of trials). Consider also these words:
[I]t has to be recognized that, while there is no reason to suppose that policemen as individuals are any less fallible than other members of society, people are often shocked and outraged when policemen are exposed violating the law. The reason is simple. Their deviance elicits a special feeling of betrayal. In a sense, they are doubly condemned; that is, not just for the infringement itself but even more for the breach of trust involved. Something extra is involved when public officials in general and policemen in particular deviate from accepted norms: “That something more is the violation of a fiduciary relationship, the corruption of a public trust, of public virtue.“
If it is a violation of a “fiduciary relationship” for a police officer to lie, it one as well for an IRS agent to lie.