Michael Mukasey is far from being a Washington insider, having spent his entire career in New York.
Michael Mukasey is considered a law-and-order conservative
President George W Bush turned to someone outside his inner circle when he nominated Mr Mukasey as US attorney general in September 2007.
Mr Mukasey is known as a law-and-order conservative with an independent frame of mind as well as an acknowledged authority on national security issues.
Mr Mukasey's nomination as attorney general was nearly derailed by a controversy in his confirmation hearing, when he refused to say whether he believed an interrogation technique that simulates drowning was torture.
But he survived a Senate committee vote and his nomination was approved by the full Senate.
As a federal judge in Manhattan, serving in one of the country's busiest courts, Mr Mukasey presided over some high-profile terrorism trials.
These included the 1993 prosecution of Omar Abdel Rahman, known as the "Blind Sheikh", whom he sentenced to life in prison for his role in a plot to blow up New York landmarks and tunnels.
His connection with that case meant he lived under heavy federal security for years, the Washington Post reported.
In 2002, Mr Mukasey issued the first rulings in the prosecution of US citizen Jose Padilla. Mr Mukasey backed the White House's view that Padilla could be held as an enemy combatant, although his decision was later overturned on appeal.
But he went against the Bush administration by ruling that Padilla was entitled to legal counsel.
He has spoken in favour of the Patriot Act, passed after the 9/11 attacks, and rejected criticisms that the act gave the government too much power to spy on ordinary Americans.
In an opinion piece for the Wall Street Journal, Mr Mukasey said the Padilla case and others showed that the criminal justice system was inadequate for trying terrorism defendants. He proposed an alternative system for dealing with such cases.
Some Democrats, including some of the fiercest critics of Mr Mukasey's predecessor, Alberto Gonzales, looked favourably on the nomination of Mr Mukasey.
"While he is certainly conservative, Judge Mukasey seems to be the kind of nominee who would put rule of law first and show independence from the White House, our most important criteria," said Sen Chuck Schumer, a senior Democratic Party member of the Senate Judiciary Committee.
Sen Schumer voted in favour of Mr Mukasey's nomination, saying that although Mr Mukasey's refusal to state that water-boarding was illegal was "unsatisfactory", he was a "strong leader, committed to depoliticising the agency's operations".
Mr Mukasey, who was born in July 1941, was nominated for the post of federal judge in 1987 by then President Ronald Reagan.
Mr Mukasey spent 19 years on the US District Court for the Southern District of New York, which includes Manhattan, including six as the chief judge before he retired in 2006 to enter private law practice.
Earlier in his career, Mr Mukasey worked in the federal prosecutor's office in New York for four years.
Mr Mukasey graduated from Columbia College and Yale Law School.