From a judge:

As a judge I have to be very careful about going outside the “four corners”
of the record before me in deciding a case. Clearly, some internet research
is appropriate–Lexis-Nexis. But, if I tried to resolve a factual dispute
in the record by doing my own research I believe I would overstepped the
bounds of my ethics. That is the parties jobs and they have burdens of
proof to meet. The judge is the finder of fact and is not supposed to be
the developer of fact.
Especially appellant judges, who are to review the record before them as
developed at the lower level. These judges are not supposed to be
supplementing or developing the facts. A judges role is similar to that of
a jury–to review the facts presented. It is improper for a juror to do
research on factual issues and it might also be for a judge. Thus, a
blanket condemnation of Mr. Delay’s comments is not necessarily appropriate.