You might note, in the above paragraph, that the Constitution does not specifically state that a Supreme Court justice is appointed for life. Rather, it says the justices “shall hold their Offices during good Behaviour,” which has always been understood to mean until he or she died, retired or was impeached for bad “Behaviour.”
Unlike the president, who can be removed only if convicted of “high crimes and misdemeanors,” a justice can theoretically be removed for anything short of “good Behaviour,” which is not defined at all in the document and would seem to leave room for any amount of mischief.
But this hasn’t occurred. Only one justice in history, Associate Justice Samuel Chase in 1805, has ever been impeached, which is the first step in the removal process, the one that occurs in the House. But he was not convicted at his Senate trial and was not removed.