"Michael 182" wrote in message
news:_lYlb.4765$mZ5.23361@attbi_s54...

You wouldn't from the scope, but there are plenty of days when the
conditions are well known. Do you mean you have no idea what the cloud
conditions are as a controller? Not such that you can decide if he is
violating VFR, but enough to know, at least in your own head, that there
is
no way this guy is VMC...


You would need a PIREP from someone at the same spot at the same time.