“(4) That, in order to obviate the practice, there must be some miscarriage of justice or violation of some principle of law or procedure. That miscarriage of justice means such a departure from the rules which permeate all judicial procedure as to make that which happened not in the proper sense of the word judicial procedure at all. That the violation of some principle of law or procedure must be such an erroneous proposition of law that if that proposition be corrected the finding cannot stand; or it may be the neglect of some principle of law or procedure, whose application will have the same effect. The question whether there is evidence on which the courts could arrive at their finding is such a question of law. (5) That the question of admissibility of evidence is a proposition of law, but it must be such as to affect materially the finding. The question of the value of evidence is not a sufficient reason for departure from the practice. (6) That the practice is not a cast-iron one, and the foregoing statement as to reasons which will justify departure is illustrative only, and there may occur cases of such an unusual nature as will constrain the Board to depart from the practice.”
“Where (as here) the entirety of the issues in the appeal concern concurrent findings of fact, the Board is likely to require the appellant to demonstrate, as a preliminary condition, that there exist exceptional circumstances which justify a departure from the practice, before the Board will proceed with the appeal any further.”