radio button validation?

I have a feature request, which I understand from the archives might
involve a great deal of work, but I figured I'd throw it out there to
see what kind of response there is.

http://www.w3.org/TR/html4/interact/forms.html#radio says that
'authors should ensure that in each set of radio buttons that one is
initially "on".'

Is there any way to get the validator to check for conditions like this?

Thanks,
  Bill