Thursday's public ethics committee hearing that laid bare the 13 charges against Rep. Charles Rangel was a highly unusual event -- but not because congressional lawmakers rarely break the rules.

The House and Senate have for years steered clear of filing charges against their own, and are even more reluctant to mete out punishment when someone is found guilty of a violation.

In the past 13 years, just one House lawmaker has filed an ethics complaint against another member, which is one of the few ways an investigation can be initiated. Members have instead abided by a bipartisan ethics "truce" that some believe has silently stifled the ethics process since the waning days of former House Speaker Newt Gingrich.

"The House ethics committee simply serves as a cover for members to engage in improper conduct," said Melanie Sloan, executive director of the ethics watchdog group Citizens for Responsibility and Ethics in Washington. "It's like high school. members like to cover for each other."

In many cases, the ethics committee has started investigations only after the media has exposed a potential violation, as was the case with former Majority Leader Tom DeLay, R-Texas, who became the subject of an ethics investigation after reports showed he had offered to endorse the candidacy of a lawmaker's son in exchange for a critical House vote on Medicare reform.

Once opened, ethics probes often drag on for months and even years, as was the case with Rangel, who the panel began investigating in 2008. At the conclusion of most investigations, members have typically received a slap on the wrist and a softly worded admonishment.

DeLay, for instance, wasn't really punished at all by the ethics committee, even though the panel said he violated the rules. Instead, the committee decided the report itself would serve as punishment.

The last time the House actually held a public hearing and expelled a member was in 2002, after then-Rep. Jim Traficant was convicted on federal corruption charges and was headed to prison anyway. Before that, the only people expelled from the House were ousted for donning Confederate uniforms -- in 1861.

The ethics panel publicly charged Rangel on Thursday only after failing to cut a deal privately with the embattled lawmaker.

"One of the most difficult tasks assigned to a member of Congress is to sit in judgment of a colleague," Rep. Gene Green, D-Texas, who helped conduct the Rangel investigation, said at the ethics hearing Thursday. "The task is even more difficult when the subject of the investigation has befriended and mentored so many new members of Congress, myself being one of them."