U.S. President Donald Trump is scheduled to announce his nominee for the Supreme Court Tuesday night.

Neil Gorsuch, Thomas Hardiman and William Pryor are the three federal appeals court judges who are seen as the leading candidates.

Each was appointed to the appellate bench by President George W. Bush. Each appeared on Trump's list of 21 possible choices that he made public during the campaign, and each has met with Trump to discuss the vacancy that arose when Justice Antonin Scalia died nearly a year ago.

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GORSUCH

Gorsuch, 49, serves on the 10th U.S. Circuit Court of Appeals in Denver, where he has made a name for himself as a facile writer. Gorsuch is a graduate of Columbia University and Harvard Law School, and served as a law clerk to Justices Anthony Kennedy and fellow Coloradan Byron White. If chosen, he would be the first justice to serve with a colleague for whom he once worked.

With a clear, colloquial writing style, Gorsuch has written in favour of courts' second-guessing government regulations, in defence of religious freedom and skeptically about law enforcement. He has contended that courts give too much deference to government agencies' interpretations of statutes. He sided with two groups that mounted religious objections to the Obama administration's requirements that employers provide health insurance that includes contraception for women.

He is the son of The son of President Ronald Reagan's Environmental Protection Agency chief, Anne Gorsuch. He worked for two years in Bush's Justice Department before Bush appointed him to his appeals court seat. He was confirmed by a voice vote in 2006.

Gorsuch has written 175 majority opinions and 65 concurrences or dissents in his decade on the 10th Circuit, according to Rebecca Love Kourlis, a former Colorado Supreme Court justice.

Gorsuch also is a notable advocate for simplifying the justice system to make it more accessible, Kourlis said.

Gorsuch is also an avid skier, fly fisherman and horseback rider, Kourlis said. He teaches at the University of Colorado's law school in Boulder.

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HARDIMAN

Hardiman, 51, works in Pittsburgh as a judge on the Philadelphia-based 3rd U.S. Circuit Court of Appeals. He drove a taxi to support himself during his undergraduate years at the University of Notre Dame. He received his law degree from Georgetown University. Hardiman became a partner in a major law firm at age 30 and a federal district judge at 38.

The Senate confirmed him 95-0 to his current job in April 2007. His prominent opinions on the appeals court include siding with jails seeking to strip search inmates arrested for even minor offences and backing the collection of genetic evidence from people at the time of their arrest. Hardiman has supported gun rights, dissenting in a 2013 case that upheld a New Jersey law to strengthen requirements to carry a handgun in public.

Hardiman last year joined two 3rd Circuit colleagues in affirming the $1 billion settlement of NFL concussion claims, rejecting complaints that men with depression and mood disorders that some link to football concussions were left out of the deal. In earlier oral arguments. The Supreme Court later refused to hear the challengers' appeal.

Hardiman was raised in Waltham, Massachusetts, and eventually settled in Pittsburgh, where his wife comes from a family of prominent Democrats. The Hardimans have three children.

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PRYOR

Pryor, 54, has his office in Birmingham, Alabama, where his sits as a judge on the Atlanta-based 11th U.S. Circuit Court of Appeals. He's been on the court since 2004, when Bush gave him a temporary recess appointment to get around Democratic opposition in the Senate. He was confirmed by a 53-45 vote in 2005, part of a bipartisan deal to limit Senate delays of appellate nominations.

Pryor has a reputation as staunch conservative. He once called the 1973 landmark Roe v. Wade decision legalizing abortion the "worst abomination in the history of constitutional law."

On the bench, Pryor has often ruled against criminal defendants. He authored a majority opinion upholding a border patrol agent's decision to stop a SUV filled with Hispanic passengers because the vehicle was driving erratically and the occupants appeared nervous. He also ruled that a Supreme Court decision banning automatic life sentences for juvenile defendants should not be applied to older cases. The high court later disagreed, ruling that the decision did apply retroactively.

On religious freedom, in 2014, he wrote a separate opinion in favour of a Catholic television station that objected to the contraception coverage mandate of the Affordable Care Act.

The son of two teachers, Pryor traced the roots of his conservatism to his staunch Catholic upbringing. He said the abortion ruling, handed down when he was a boy, influenced his decision to become a Republican and a lawyer. Pryor grew up in Mobile, Alabama, and graduated from Tulane Law School in New Orleans. He was a law clerk to Judge John Minor Wisdom, whose rulings helped end segregation.

Pryor was appointed Alabama's attorney general at age 34. He succeeded Jeff Sessions, the Alabama senator nominated to be Trump's attorney general.