If the material was not brought up in court, the judge, his mother, his staff cannot independently investigate it. The reason is because the parties don't get a chance to defend themselves. In Europe, yes, a judge has investigative authority. Not in the U.S. Same reason why the jury are told not to watch the news/read internet pertaining to their case - BECAUSE IF IT WASN'T BROUGHT UP ON COURT, AS FAR AS COURT IS CONCERNED, IT DIDN'T HAPPEN.