The purposes of this Part are—
(a) to assist the trial judge to discharge his or her duty to determine—
(i) the matters in issue in the trial; and
(ii) the directions that he or she should give to the jury; and
(iii) the content of those directions; and
(b) to ensure that legal practitioners appearing in a criminal trial discharge their duty to assist the trial judge in his or her determination of the matters referred to in paragraph (a); and
(c) to provide for the directions that the trial judge should give to the jury if the accused is not represented by a legal practitioner.