Carter Vincent Boehm, a Northern Virginia real estate broker facing federal drug charges and linked to the cocaine possession case against developer Mark R. Vogel, worked as a volunteer advance man for the White House on at least four occasions over the past year.

A White House spokeswoman confirmed that Boehm, 41, last worked as an unpaid assistant on the presidential advance team in July, a month after he was indicted in connection with a scheme to trade machine guns for cocaine. The spokeswoman declined to specify Boehm's duties or the level of his access to the president.

"Mr. Boehm participated on a voluntary basis in a trainee capacity as an assistant to the advance office in four separate events over a one-year period," said Alixe Glen, deputy press secretary for the White House.

Glen declined to specify the events. Glen said that an assistant trainee's duties generally are menial and can range from setting up chairs to serving coffee.

Robert Snow, a spokesman for the Secret Service, declined to say whether Boehm had security clearance, citing confidentiality requirements. However, Snow said that all volunteer assistants undergo cursory background and criminal history checks and are subject to more rigorous examination if they come in close contact with the president.

The background check is generally done only when the person joins the staff or changes jobs and may not uncover pending criminal charges, Snow said.

Sources said that Boehm worked for Mel Lukens, a presidential advance representative.

Lukens, located in Omaha, where he is preparing for a presidential visit, confirmed that he knew Boehm but declined to discuss his job. "I know Carter and I know of his little troubles . . . but at this particular moment I couldn't tell you what trips he did," Lukens said. "To be very honest with you, I don't know if I'd really want to. This comes as a bit of a shock to me."

Nicholas Balland, Boehm's attorney, said, "I have been aware that Mr. Boehm was working for the White House . . . but there is absolutely no connection between the federal indictment in Charlottesville and any of the activities he performed for the White House." Boehm resigned his position with the advance team two weeks ago, Balland said.

Boehm was indicted by a federal grand jury in Virginia on June 22 and is awaiting trial on charges of conspiracy to possess cocaine for distribution, subornation of perjury (inducing another person to commit perjury) and tampering with a witness.

Balland declined to comment on the indictment or other drug allegations involving Boehm.

The indictment alleges that Boehm offered an associate $50,000 to obtain a kilogram of cocaine. That associate and another person were arrested when they attempted to trade two automatic weapons to an undercover agent of the Bureau of Alcohol, Tobacco and Firearms for a kilogram of cocaine, according to the indictment.

Boehm owns the Carter Boehm Co. of Alexandria and Townside Partners Realty and has been active in Northern Virginia real estate for several years.

Boehm also is a close friend and business partner of Vogel, who was arrested on a cocaine possession charge on Sept. 13 in Fairfax County. Vogel, the owner of Maryland's two harness racing tracks, told investigators that he was en route to Boehm's Great Falls home to use cocaine when he was arrested, according to a federal affidavit filed last month.

Vogel plans to plead not guilty, according to his lawyer, Plato Cacheris.

Federal law enforcement sources have said that both men are among a circle of developers and lawyers who are under investigation for alleged drug activity.

A separate federal investigation also has focused on allegations of political influence-peddling and corruption involving some of the same people, law enforcement sources said.

Associates of Boehm said that he wore a White House advance team earpiece, which operates on a different channel than the Secret Service detail, and was involved in tracking the movements of the president at events.

They said that he traveled to Wyoming in July for a Bush event and that on several occasions used his Secret Service clearance to admit friends to events.

Three of the events where Boehm worked were in the District, sources said. One of those events, sources said, was a $1,000-a-plate black-tie gala at the Omni Shoreham Hotel on May 1 to raise money for the National Memorial to Veterans of the Korean War.

White House personnel said that they could not confirm whether Boehm had traveled to Wyoming.

Staff writer Ann Devroy contributed to this report.