...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 from the same; and for any Speech or Debate in either House, they shall not be questioned in any other Place.
The intended purpose is to prevent a President or other officials of the executive branch from having members arrested on a pretext to prevent them from voting a certain way or otherwise taking actions with which the President might disagree.
A similar clause in many state constitutions protects members of state legislatures in the United States. Legislators in non-U.S. jurisdictions may be protected by a similar doctrine of parliamentary immunity.
On June 15, 1971, SenatorMike Gravel (D-Alaska) received a copy of the Pentagon Papers from Ben Bagdikian, an editor at The Washington Post. Over the next several days, Gravel (who was dyslexic) was assisted by his congressional office staff in reading and analyzing the report. Worried his home might be raided by the Federal Bureau of Investigation, Gravel smuggled the report, which filled two large suitcases, into his Senate office, which was then guarded by disabled Vietnam veterans.
On the evening of June 29, 1971, Gravel attempted to read the Pentagon Papers into the Congressional Record. A lack of a quorum, however, prevented the Senate from convening. As chair of the Senate Subcommittee on Public Buildings and Grounds, Gravel convened a meeting of the subcommittee and spent an hour reading part of the Pentagon Papers into the record. Prevented by his dyslexia from continuing, Gravel had the remainder of the Pentagon Papers entered into the record.
A federal grand jury was empaneled to investigate possible violations of federal law in the release of the report. Leonard Rodberg, a Gravel aide, was subpoenaed to testify about his role in obtaining and arranging for publication of the Pentagon Papers. Senator Gravel intervened and asked a court to quash the subpoena, contending that forcing Rodberg to testify would violate the Speech or Debate Clause. A federal district court refused to grant the motion to quash but did agree to proscribe certain questions. The trial court also held that publication of the Pentagon Papers by a private press was not protected by the Speech or Debate Clause. The Court of Appeals affirmed the district court's ruling, although it modified the categories of barred questions. The United States appealed the barring of questions, and Senator Gravel appealed the ruling regarding publication. The United States Supreme Court granted certiorari.
In Gravel v. United States,408 U.S. 606 (1972), the Supreme Court held (5-4) that the privileges of the Speech or Debate Clause extend to Congressional aides. Rejecting the reasoning of the Court of Appeals, the Supreme Court held, "...the privilege available to the aide is confined to those services that would be immune legislative conduct if performed by the Senator himself," the Court declared.
The Court refused to protect congressional aides either from prosecution for criminal conduct or from testifying at trials or grand jury proceedings involving third-party crimes. The Supreme Court also vacated the lower court's order permitting some questions and barring others, concluding that if the testimony is privileged then the privilege is absolute.
The Supreme Court upheld the district court ruling regarding private publication. "[Private] publication by Senator Gravel through the cooperation of Beacon Press was in no way essential to the deliberations of the Senate; nor does questioning as to private publication threaten the integrity or independence of the Senate by impermissibly exposing its deliberations to executive influence."
The Gravel case narrowed the protections offered by the Speech or Debate Clause.
In May 2006, following an FBI raid on the Capitol Hill office of Rep. William J. Jefferson (D-LA), some members of Congress have criticized the FBI's search as an unconstitutional breach of this clause. Those who support the FBI's position contend that the clause did not apply to the search of Jefferson because he was alleged to have committed felonies of accepting bribes, obstructing a previous search, and storing in a freezer the money he accepted in bribery. Also, Jefferson was not arrested at the House, and the FBI investigation does not concern anything Jefferson said at Congress.
The U.S. Court of Appeals for the District of Columbia Circuit ruled that the search was unconstitutional. The Supreme Court declined to review the D.C. Circuit Court's decision. The search of the accused Jefferson’s House office was found to be unconstitutional because of a “filter team’s” review of all legislative files in that office.
On September 24, 2008, Jefferson argued before the Fourth Circuit Court of Appeals that as his legislative acts were part of the evidence used to indict, they fell under the Clause and the indictment should be vacated. The Court of Appeals rejected this contention.
On August 6, 2006, Marine Corps Staff Sergeant Frank D. Wuterich, who led a squad of Marines into Haditha, Iraq that killed 24 civilians, filed suit for libel and invasion of privacy. Wuterich claims that Congressman John Murtha's comments at a news conference on May 17, 2006 and, in subsequent television interviews, tarnished the Marines' reputation and constituted an invasion of privacy.
A federal judge ruled on September 28, 2007 that Murtha must testify at the Haditha defamation case. Commentators have expressed concern that Murtha was acting as lawmaker and was therefore protected by the Speech or Debate Clause. Murtha, the Justice Department, and the House's General Counsel never filed an appeal. In 2009, an appellate court dismissed the case citing Mr Murtha's role as a lawmaker. The appellate court dismissed Mr Murtha from the case pursuant to the Westfall act which immunizes Federal employees for official acts