How do you justify an unelected and unaccountable court in a democracy?

The U.S. Supreme Court is unelected and its members, once appointed, cannot be removed regardless of the decisions they make except through impeachment. How do you justify an unelected and unaccountable court in a democracy? Write an essay in which you describe the role played by the US Supreme Court in the US political system and discuss how and in what ways it is compatible or incompatible with democratic theory