Does the “Speech and Debate Clause” Shield Congress?

Today’s Washington Post has an interesting article detailing Justice Department concerns that the Constitution’s Speech and Debate Clause has frustrated investigations into Congressional wrongdoing.  The clause provides, in relevant part, that members of Congress:

shall in all Cases, except Treason, Felony and Breach of the Peace, be privileged from Arrest during their Attendance at the Session of their respective Houses, and in going to and returning from the same; and for any Speech or Debate in either House, they shall not be questioned in any other Place.

As interepreted by federal courts, this clause limits the Executive Branch’s ability to investigate legislators conduct on Capitol Hill. In one infamous case (discussed here), the U.S. Court of Appeals for the D.C. Circuit held the FBI violated the clause when it seized allegedly privileged documents from the office of Rep. William “Cold Cash” Jefferson.  Reports the Post:

The Justice Department warned at the time that the court decision would “seriously and perhaps even fatally” undermine congressional corruption probes by limiting the FBI’s ability to search for evidence and use wiretaps.

Since then, speech or debate challenges have killed an investigation of former representative Tom Feeney (R-Fla.), hampered probes of Rep. Peter J. Visclosky (D-Ind.) and former representative John T. Doolittle (R-Calif.), and slowed a pending corruption case against former representative Rick Renzi (R-Ariz.), sources familiar with those inquiries said. . . .

lawyers familiar with the issue said speech or debate concerns come up in virtually every congressional probe because many involve legislative acts, such as whether the lawmaker obtained earmarks in exchange for campaign contributions.

“The essence of speech or debate is you can’t introduce into evidence what the member did if it’s part of an official duty,” said a lawyer who spoke on the condition of anonymity because the challenges are often under court seal. “If you can’t introduce legislation, a bill, a speech on the floor, how do you make the case?”