In his dissent from the Supreme Court’s ruling on Arizona’s immigration law, Justice Antonin Scalia’s bizarre off-topic rant suggests that he can no longer judge what is appropriate to his current courtroom activity.
(See http://www.washingtonpost.com/opinions/justice-scalias-partisan-discredit-to-the-court/2012/06/27/gJQAoVEG7V_print.html and http://www.washingtonpost.com/opinions/ej-dionne-jr-justice-scalia-should-resign/2012/06/27/gJQApkO06V_print.html)
This, together with the blatantly partisan character of his previous recent rants (see the URLs above) seriously undermine confidence that he is still judicially competent.
Indeed, Scalia’s impaired ability to judge the appropriateness of his behavior may be an early sign of dementia. Although most 76 year olds have not developed dementia, a non-negligible fraction have, or are beginning to do so. He ought to see a neurologist.