Mukasey was sworn in at a private Justice Department ceremony about 16 hours after he narrowly won Senate confirmation. The third attorney general of the Bush administration, Mukasey, 66, inherits a Justice Department struggling to restore its independent image with more than a dozen vacant leadership jobs and little time to make many changes before another president takes office.

Justice Department spokesman Brian Roehrkasse said Mukasey was joined by family members at the closed-door ceremony lasting two to three minutes. After taking the oath, Mukasey headed immediately into meetings with senior Justice Department officials, including a briefing on the Foreign Intelligence Surveillance Act.

Mukasey "got right to work," Roehrkasse said.

Mukasey served nearly two decades as a federal district judge in Manhattan and oversaw many of the nation's highest profile terror cases in the aftermath of the Sept. 11, 2001 attacks. He now has 14 months to turn around the demoralized Justice Department and its 110,000 employees after almost a year of scandal that forced the resignation of his predecessor and cast doubt on the government's ability to prosecute cases fairly.

Andrew Kent, a constitutional law professor at Fordham Law School in the Bronx, said it's unclear how much Mukasey can get done.

"It just seems inconceivable that there'd be any major changes in legal policy, in the president's approach to the war on terror at the behest of an outsider to the administration - which is what Mukasey is," Kent said.

Mukasey's first full day on the job will be Tuesday. A public swearing-in ceremony is being planned for next week, and Mukasey is expected to address Justice Department employees for the first time afterward.

The Senate confirmed Mukasey minutes before midnight Thursday by a 53-40 vote - which critics noted marked the narrowest margin to confirm an attorney general in more than 50 years. His confirmation briefly stalled over his refusal to say whether he considers an interrogation tactic known as waterboarding a form of illegal torture.

But Mukasey made clear to senators he won't tolerate politics influencing decisions about prosecuting cases or hiring career attorneys - allegations being investigated now in an ongoing inquiry into last year's firings of nine U.S. attorneys.

The scandal, which led to Gonzales' ouster in September, tarnished the Justice Department's long-held independent image and prompted a flood of resignations from its senior officials.

Twelve of the highest-ranking department jobs - including the No. 2 and 3 spots and six assistant attorney generals - currently are held by officials who have not been confirmed by the Senate. Two other senior officials have announced their resignations and are expected to leave shortly.

Having temporary officials filling in at the top jobs creates some uncertainty in the department, said William Barr, who was attorney general during the administration of former President George H.W. Bush.

"It could affect their ability to be decisive on issues because everything they do could potentially become an issue in their confirmation," said Barr, now general counsel at Verizon Communications Inc.