Q&A: US Supreme Court

Sonia Sotomayor has been confirmed as the 111th American to sit on the US Supreme Court.

Supreme Court justices serve for life, so Ms Sotomayor could be on the court for decades and leave a lasting imprint on American life.

How are Supreme Court justices appointed?

The constitution gives the president sole authority to appoint Supreme Court justices.

However, any appointment he makes must be approved by a majority vote in the Senate.

Before facing a vote, nominees are called before the Senate Judiciary Committee where they are asked to testify about their judicial philosophy.

Has the Senate ever blocked a president's appointment?

Yes. In 1987, the Democrats (who held a majority in the Senate) voted down President Ronald Reagan's nominee for the Supreme Court, Robert Bork.

The Democratic Senators objected to Mr Bork's views on abortion and executive power.

The Senate has rarely used its power to block nominees, however.

What is so important about the Supreme Court?

The Supreme Court is the highest court in the US and has the authority to strike down any state or federal law it deems unconstitutional.

It is regularly called upon to rule on issues of individual freedom - such as civil rights and free speech - or life-and-death matters like abortion.

These involve basic constitutional principles that fall under the court's purview.

Its landmark cases have shaped modern America, such as Brown v Board of Education in 1954, which signalled the end of legal segregation, Roe v Wade in 1973, which secured the right to abortion, or the 1976 decision allowing states and federal legislators to impose the death penalty.

So the decisions made by the nine justices on the Supreme Court can have a huge impact on American life.

Cases are decided by majority vote of the justices.

How long do justices serve on the Supreme Court?

Once appointed, justices can - if they want to - serve on the court for the rest of their lives.

They are allowed to retire or resign, and can be forced out of office by congressional impeachment.

Potentially, however, and in practice, Supreme Court justices serve on the court for decades.

What is the political make-up of the Supreme Court?

Although their life-tenure gives Supreme Court justices independence from partisan politics, they are appointed (and approved) by politicians, so the Supreme Court is far from being a politics-free zone.

And because their decisions carry so much weight, the political views of the Supreme Court are a subject of much interest and debate.

At present, four of the nine justices can broadly be described as liberal (Stephen Breyer, Ruth Bader Ginsburg, David Souter and John Paul Stevens) and four can be described as conservative (John Roberts, Antonin Scalia, Clarence Thomas and Samuel Alito).

The ninth justice - Anthony Kennedy - is a swing voter, sometimes siding with liberals, sometimes with the conservatives.

Will Justice Souter's retirement change the political balance of the court?

Unlikely. President Obama, a liberal, has chosen another liberal - Sonia Sotomayor - to replace David Souter, also a liberal.

Having said that, past justices have turned out to hold very different views from the presidents who appointed them. Indeed, Justice Souter himself was appointed by a Republican president (George H W Bush).

Once Ms Sotomayor ascends to the bench, she will be free to change her views.

But she is not expected to shift her views radically, so her appointment is expected merely to maintain the political status quo on the court.

Unless one of the conservative justices dies or retires, Mr Obama is unlikely to be able to alter the political make-up of the court.