Stefan Buck, former head of private banking of Bank Frey took his case to trial in New York. And he won. He was was acquitted of all allegations.
This has dealt US prosecutors a dramatic loss. The Department of Justice has had a spotty record prosecuting more than three dozen offshore bankers, lawyers and advisers charged with enabling tax evasion by U.S. clients. While several have pleaded guilty, at least three, including Buck, have been acquitted by jurors.
Here are the links to a number of articles on the topic for your convenience:
National Law Review