For instance, any time anything such as conversations or e-mail or documents contain a mixture of privileged and unprivileged information, lawmakers will have an easier time arguing that all of the information should be protected.

Jefferson’s case was delayed while a judge determines which material is admissible in the case. He is accused of masterminding an elaborate scheme to promote business interests in Africa and faces 16 counts, including bribery, racketeering and money-laundering.

William Heaton, a top aide to former Rep. Bob Ney (R-Ohio), wore a wire for a 2 1/2 hour conversation that bolstered the case against the House GOP member. Ney subsequently pleaded guilty and was sent to prison.

Jefferson’s phones were tapped during the raid of his New Orleans home, according to evidence admitted during pre-trial hearings. More than two years ago — when legislators were focused on the question of who else might be brought down by ex-lobbyist Jack Abramoff’s cooperation with prosecutors — members discovered that former Rep. Randy “Duke” Cunningham (R-Calif.) wore a wire to help investigators gather evidence against others before negotiating his own plea.

In 1988 several members of Congress, were caught in wiretaps as part of a nationwide investigation on allegations of widespread fraud and bribery within the Department of Defense and the defense industry.

More than a dozen government officials were convicted of crimes, including an Assistant Secretary of the Navy, a Deputy Assistant Secretary of the Navy, and a Deputy Assistant Secretary of the Air Force. Another 60 private citizens, including lobbyists for major defense contractors, were convicted.

The scandal spurred Congress to pass the Procurement Integrity Act, which regulates the pay that procurement officials can get from contractors during the first year after they leave government.

Mike Soraghan contributed to this report.