Section 344.3. Rules of evidence; psychiatric testimony in certain cases

When, in connection with a  defense  of  mental  disease  or  defect,  a
  psychiatrist  or  licensed  psychologist who has examined the respondent
  testifies at the fact-finding hearing concerning the respondent's mental
  condition at the time of the conduct charged to constitute a  crime,  he
  must  be  permitted  to  make  a  statement  as  to  the  nature  of the
  examination, the diagnosis of the mental condition of the respondent and
  his opinion as to the extent, if any,  to  which  the  capacity  of  the
  respondent  to  know  or  appreciate the nature and consequences of such
  conduct, or its wrongfulness, was impaired as a result of mental disease
  or defect at that time. The psychiatrist must be permitted to  make  any
  explanation reasonably serving to clarify his diagnosis and opinion, and
  may  be  cross-examined  as  to  any matter bearing on his competency or
  credibility or the validity of his diagnosis or opinion.