(a) Exceeded its jurisdiction;
(b) Failed to follow the procedure applicable to the matter before it;
(c) Made a finding or order not supported by substantial evidence in the whole record;
(d) Improperly construed the applicable law; or
(e) Rendered a decision that is unconstitutional.
(2) The fact that the right of appeal exists is no bar to the issuance of the writ. [Amended by 1965 c.292 §1; 1973 c.561 §1; 1979 c.772 §13; 1995 c.79 §12; 1995 c.658 §29]