In almost every term, the [Supreme Court Justices] exercise veto power over fundamental policy questions such as abortion, gun control and freedom of speech and religion. There can be no denying the political and legal responsibility we place in these nine justices.
The original rationale for this highly anti-democratic idea [of life terms] was that the justices needed to be independent from the elected branches so that they could enforce the Constitution and decide cases without fear of political retaliation. But the Founding Fathers did not anticipate that the justices would be appointed so young and live so long.
Because the justices hold their offices for life, there are many examples of some who serve too long. As the historian David Garrow noted in his 2000 analysis of the problem, “mental decrepitude among aging justices is a persistently recurring problem.”