DOUGLAS GINSBURG, Federal Judge, U.S. Court of Appeals, D.C. Circuit:
Justices of the Supreme Court, if they choose not to retire, may serve for life – though the Constitution doesn’t actually say that. What it says is that federal judges “shall hold their offices during good behavior….” Which suggests that a justice can be removed for bad behavior.

Of the more than one hundred justices who have served on the Supreme Court, only one was impeached – that was back in 1804. Justice Samuel Chase was a signer of the Declaration of Independence who was appointed to the Court by President Washington. His rulings so annoyed some members of the House of Representatives, that they voted to impeach him. But the Senate acquitted Chase – and thereafter the Court remained independent of partisan whims.

Only one justice resigned under threat of impeachment. Justice Abe Fortas left the Court in 1969 amid a financial scandal. The House has impeached fourteen judges from the lower federal courts; the Senate acquitted three, the rest were convicted.
In the early years of the republic, when life expectancy was shorter, most justices died in office. After 1900, the trend reversed – most justices retired. I clerked for Justice Thurgood Marshall, who was appointed by President Lyndon Johnson – a Democrat. He was succeeded by Richard Nixon – a Republican.
Soon after President Nixon took office, Marshall fell ill and was in the hospital. One day Marshall was told that President Nixon had called while he was asleep. Marshall said that if the president called again, to give him this two-word message: Not yet.
I like to refer to the appointment of any federal judge as a life sentence. Even those who do step down seldom pursue another career.