U.S. Rep. Louis Stokes, a veteran Ohio Democrat, was stopped by Montgomery County police early Friday morning and failed a series of roadside sobriety tests, but he was not arrested because he claimed congressional immunity under a seldom-used section of the U.S. Constitution, according to county police.

Stokes, 58, chairman of the House ethics committee and a former chairman of the Congressional Black Caucus, was spotted by a patrol car about 2:15 a.m. Friday driving down the wrong side of six-lane Randolph Road in Wheaton, police said. Police allege that the congressman then made an illegal U-turn, ran a red light and began to make another illegal turn onto Georgia Avenue.

"At that point the officer stopped him and detected the odor of alcohol," said Montgomery Police Sgt. Harry Geehreng. "He was swaying and gave the impression of being under the influence."

Geehreng said Stokes failed three roadside tests after being stopped by the patrol officer, including reciting the alphabet, walking a straight line and touching his finger to his nose. "He missed a couple of letters," said Geehreng, "and was unable to do" the other tests.

Stokes identified himself as a congressman and claimed congressional immunity under Article 1, Section 6 of the Constitution which says members of the House of Representatives and Senate are exempt from arrest while in session, and traveling to and from work, except in cases of treason, felony or breach of the peace, police said.

Greehreng said a Montgomery County police official called the U.S. Capitol police to verify whether Stokes could claim congressional immunity and was told that he could because he was on his way home from a late-night session. Stokes' wife went to the Wheaton-Glenmont police station, a block from where he was stopped, Geehreng said, and picked him up. Stokes, who lives in Silver Spring, was stopped about two hours after Congress recessed late Thursday.

According to Stanley Brand, general counsel to the House of Representatives, the immunity section in the Constitution was originally intended to prevent harassment of colonial legislators by civil litigants or those acting under orders of the executive branch.

An attorney for the Montgomery County police later agreed with the Capital police's judgment that Stokes could claim immunity because he was en route home from a congressional session, and, that his alleged conduct did not necessarily constitute a breach of the peace, Geehreng said. Montgomery County police will not seek to press charges against Stokes, Geehreng said.

Police said Stokes left for the Middle East later that day. His office on Capitol Hill had no comment.