What to know about the backgrounds of all 9 U.S. Supreme Court justices

Supreme Court justices are at the top tier of the U.S. court system.

The judicial branch is the third branch of U.S. government established by the U.S. Constitution. The two others are the executive (president) and legislative (Congress).

Nine justices serve on the Supreme Court. They take cases designed to clarify complex legal matters, many of which come to them after conflicting opinions from lower courts, such as the federal district and appeals courts.

The nine justices often make decisions based on interpretations of the Constitution, which was written in 1787.

From decisions involving enslaved people and segregated schools and the federal right to abortion, the justices' rulings have shaped U.S. history and policy since the court first assembled in 1790.

The court has a 6-3 conservative majority.

In its last decision of the term that ended July 1, it ruled 6-3 that former President Donald Trump could be tried for attempts he made as a candidate — but not as president — to overturn the 2020 election.

That judgment, which defined Trump's immunity from prosecution, was the court's most significant opinion and one of a half-dozen highly controversial decisions the justices made on its 59 cases in 2024.

The rulings included an order for a new review of obstruction charges against Trump and Jan. 6 defendants; a ruling that reversed a ban on bump stocks; and another that limited the regulatory authority of federal agencies.

Here's what to know about the nine justices on the court. This information comes from the U.S. Supreme Court and Ballotpedia.

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John Roberts, chief justice

John Roberts, born in January 1955, was nominated by Republican President George W. Bush as U.S. Supreme Court chief justice in 2005. He replaced William Rehnquist on the court.

Roberts serves as the 17th U.S. Supreme Court’s chief justice. A chief justice runs the logistics of the court, such as administering the oath of office to the president and vice president during the inauguration, setting the court's agendas, and assigning writings for majority opinions.

He received a bachelor of arts from Harvard College in 1976 and a law degree from Harvard Law School in 1979.

Among his decades of high-profile legal roles, Roberts was associate counsel to former President Ronald Reagan in the White House Counsel’s Office from 1982–86.

Roberts has a Martin-Quinn score of 0.43, according to the most recent 2022-23 data. Martin-Quinn scores gauge the ideology of a justice based on their voting record. Scores fall between less than zero, which indicates a liberal ideology, or a score greater than zero, which indicates conservatism.

Clarence Thomas, associate justice

Clarence Thomas, born in June 1948, was nominated by Republican President Goerge H.W. Bush in 1991 as a Supreme Court associate justice.

Thomas is the second Black justice to ever sit on the court, after he replaced Thurgood Marshall.

Before he was sworn in, Thomas attended Conception Seminary for one year in 1967 and received a bachelor of arts from the College of the Holy Cross in 1971 and a law degree in 1974 from Yale Law School.

He was a legislative assistant to Sen. John Danforth, R-Mo., and was appointed by former President Ronald Reagan as the U.S. Department of Education’s assistant secretary for civil rights. Thomas also served as chairman of the U.S. Equal Employment Opportunity Commission.

He was serving on the U.S. Court of Appeals for the District of Columbia in 1990 before his Supreme Court nomination.

Thomas was found to be one of the most conservative justices in 2022-23, with a Martin-Quinn score of 2.36.

Samuel Alito, associate justice

Samuel Alito, born in April 1950, was nominated by Republican President George W. Bush in 2006 as a U.S. Supreme Court associate justice. He replaced Sandra Day O'Connor of Arizona, who was the first woman on the court.

He served as an assistant U.S. attorney in his home state of New Jersey from 1977–81. Alito went on to work as an assistant to the solicitor general of the U.S. Department of Justice from 1981–85 and as a deputy assistant attorney general from 1985–87.

Alito returned to New Jersey as its U.S. attorney from 1987–90. Before his appointment to the Supreme Court, he served on the 3rd U.S. Circuit Court of Appeals for 15 years, starting in 1990.

He wrote the majority opinion in Dobbs vs. Jackson Women's Health Organization, the case that overturned Roe v. Wade, which federally guaranteed the right to an abortion. He was joined by justices Thomas, Gorsuch, Kavanaugh and Barrett.

He and his wife recently drew national attention for two controversial flags flown at his homes. According to the New York Times, the two flags were linked to the “Stop the Steal” movement, which made claims the 2020 election was stolen.

Alito has the highest conservative-leaning Martin-Quinn score on the court of 2.59, according to 2022-23 data.

Sonia Sotomayor, associate justice

Sonia Sotomayor, born in June 1954, was nominated by Democratic President Barack Obama in 2009 as a U.S. Supreme Court associate justice. She replaced David Souter.

Sotomayor received a bachelor of arts from Princeton University in 1976 and a law degree from Yale Law School in 1979.

She served as assistant district attorney for New York County District Attorney’s Office from 1979-84. She then practiced international commercial law in New York City until 1992.

After multiple roles in the U.S. District Court system during the 1990s, she served on the 2nd U.S. Circuit Court of Appeals until 2009.

Sotomayor has a Martin-Quinn score of -1.63, according to the most recent 2022-23 data.

Elena Kagan, associate justice

Elena Kagan, born in April 1969, was nominated by Democratic President Barack Obama in 2010 as a U.S. Supreme Court associate justice. She replaced John Paul Stevens.

She received degrees from Princeton and Oxford in the early 1980s. She earned a law degree from Harvard Law School in 1986.

Kagan clerked for U.S. Supreme Court justice Thurgood Marshall for a term in 1987 and then served as a professor at the University of Chicago Law School and later at Harvard Law, her alma mater.

She has the highest liberal-leaning Martin-Quinn score on the court of -2.06, according to the most recent 2022-23 data.

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Neil Gorsuch, associate justice

Neil Gorsuch, born in August 1957, was nominated by Republican President Donald Trump in 2017 as a U.S. Supreme Court associate justice. He replaced Antonin Scalia.

He received a bachelor of arts from Columbia University, and a law degree from Harvard Law School and a doctorate in philosophy from Oxford University. 

He clerked for the U.S. Court of Appeals for the District of Columbia Circuit and was the U.S. Department of Justice’s principal deputy associate attorney general for one year in 2005.

Gorsuch served on the 10th U.S. Circuit Court of Appeals from 2005-17.

He taught as a visiting professor in 2008 in his home state of Colorado at the University of Colorado Law School.

Gorsuch has a Martin-Quinn score of 1.08, according to the most recent 2022-23 data.

Brett Kavanaugh, associate justice

Brett Kavanaugh, born in February 1965, was nominated by Republican President Donald Trump in 2018 as a U.S. Supreme Court associate justice. He replaced Anthony Kennedy.

Born in Washington, D.C., Kavanaugh received his bachelor of arts degree from Yale College in 1987 and graduated from Yale Law School in 1990.

He clerked for the 3rd and 9th U.S. Circuit Courts of Appeals after law school.

Kavanaugh also worked for a term as a clerk for Justice Anthony Kennedy in 1993.

He had several roles during former President George W. Bush’s administration, such as associate counsel, senior associate counsel, assistant to the president and staff secretary.

From 2006 until 2018, Kavanaugh served as a judge for the U.S. Court of Appeals for the District of Columbia Circuit.

Kavanaugh has a Martin-Quinn score of 0.45, according to the most recent 2022-23 data.

Amy Coney Barrett, associate justice

Amy Coney Barrett, born in January 1972, was nominated by Republican President Donald Trump in 2020 as a U.S. Supreme Court associate justice. She replaced Ruth Bader Ginsburg.

Coney Barrett, originally from New Orleans, received a bachelor of arts degree from Rhodes College in 1994 and earned a law degree in 1997 from Notre Dame Law School.

She clerked on the U.S. Court of Appeals for the D.C. Circuit in 1997 for a year and then for U.S. Supreme Court Justice Antonin Scalia in 1998.

After her time clerking and practicing private law, she became a professor in 2002 at her alma mater Notre Dame Law School.

She was appointed as a judge on the 7th U.S. Circuit Court of Appeals in 2017.

Coney Barrett has a Martin-Quinn score of 0.82, according to the most recent 2022-23 data.

Ketanji Brown Jackson, associate justice

Ketanji Brown Jackson, born in September 1970, was nominated by Democratic President Joe Biden in 2022 as a U.S. Supreme Court associate justice. She replaced Stephen Breyer.

Originally from Washington, D.C., Jackson received a bachelor of arts degree from Harvard-Radcliffe College in 1992 and a law degree at Harvard Law School in 1996.

She clerked for a year in 1996 in the U.S. District Court for Massachusetts, clerked in 1998 for the 1st U.S. Circuit Court of Appeals and clerked for a term in 1999 for Supreme Court Justice Stephen Breyer.

Before her appointment to the U.S. Supreme Court, President Barack Obama nominated her to the U.S. District Court for the District of Columbia. She served in that role from 2013-21.

Jackson is the first Black woman to serve on the Supreme Court.

Jackson has a Martin-Quinn score of -1.71, according to the most recent 2022-23 data.

USA TODAY contributed to this article.

This article originally appeared on Arizona Republic: U.S. Supreme Court justices: political leanings, backgrounds and more