Former congressional staff member Fraser Verrusio doesn't deny taking an all-expenses-paid trip to New York arranged by lobbyists. But he disputes the government's contention that going on the trip was a crime.

Verrusio's challenge of his conviction is playing out before the U.S. Court of Appeals for the D.C. Circuit. The case is one of the last vestiges of the Jack Abramoff scandal, a wide-ranging U.S. Department of Justice corruption probe that ensnared nearly two dozen people, including lobbyists and public officials.

Verrusio's fight goes beyond clearing his name — it also implicates the freedom of members of Congress and their staff to keep information from prosecutors and defense lawyers. The case tests a constitutional protection afforded Congress known as the “speech-or-debate” clause. The protection can come into play when prosecutors — or defense lawyers — try to execute a search warrant or force a member of Congress or congressional staff into court to testify.