WASHINGTON — The nation’s spy court is moving from its longtime home at the Justice Department to a nearby federal courthouse, a move that some hope will assert the court’s independence even as Congress shifts some of its authority to the Bush administration.

Since its inception in 1978, the Foreign Intelligence Surveillance Court has been located in a secure area at Justice Department headquarters, where government attorneys armed with secret evidence seek permission to conduct surveillance.

“It’s always been an anomaly, and it suggested to critics that the court was subordinate to its Justice Department hosts,” said Steven Aftergood, director of the Project on Government Secrecy at the Federation of American Scientists.

U.S. District Judge Royce Lamberth, who presided over the court from 1995 to 2002, agreed the arrangement was never ideal because of that perception. But space at the Washington federal courthouse was scarce until the completion of an annex in 2005.

Workers recently began demolition of the old grand jury rooms, which will be replaced by a new, secure facility for the spy court. Judge Lamberth, the acting chief judge of the federal court this week, said the construction contract had not been signed but expected it to be completed soon. He expects it to cost a few million dollars. Construction is expected to take several months and the court likely won’t be moved until sometime next year.

The planned move comes after Congress voted earlier this month to strip the spy court of considerable authority. Congress, handing the Bush administration a victory on its terrorism policies, said authorities no longer need the court’s approval to eavesdrop on foreigners, even when they are talking to American citizens.