"155 Constitution of the Court Martial (1) In the case of any proceedings, the Court Martial is to consist of — (a) a judge advocate; and (b) three or, in the case of proceedings of a prescribed description, six other persons ('lay members'). (2) But Court Martial rules may provide that, in the case of proceedings of a prescribed description, there are to be — … (b) no lay members. (2A) In the case of proceedings where the number of lay members would (but for this this subsection) be three, a judge advocate may, in accordance with Court Martial rules, direct that the number of lay members is to be four. (3) In the case of proceedings where the Court Martial consists of a judge advocate and lay members — (a) a prescribed number of the lay members must be officers, warrant officers or OR-7 ranks qualified for membership under section 156 and not ineligible by virtue of section 157; and (b) the rest must be officers so qualified and not so ineligible. (4) Subsection (3) is subject to any provision made by Court Martial rules. (5) The judge advocate for any proceedings is to be specified by or on behalf of the Judge Advocate General. (6) The lay members for any proceedings are to be specified by or on behalf of the court administration officer. …"
"Interpretation: proceedings and parties 2.— (1) Unless otherwise stated, any reference in these Rules to proceedings includes — (a) preliminary proceedings, (b) trial proceedings, (c) sentencing proceedings, (d) variation proceedings, (e) appellate proceedings, (f) activation proceedings, and (g) ancillary proceedings, but does not include the exercise of any power of the court otherwise than at a hearing. (2) In these Rules— … 'preliminary proceedings' means any proceedings of the court held for the purpose of arraigning a defendant on a charge or giving directions, orders or rulings for the purpose of trial proceedings; … 'trial proceedings' means proceedings for the trial of a charge by the court (including proceedings authorised by an order of the Appeal Court under section 19 of the 1968 Act), and does not include sentencing proceedings; …"
"The court administration officer must exercise his functions (other than that of specifying the lay members for any proceedings) subject to any direction given by a judge advocate."
"Civilians 33. – (1) For proceedings to which this rule applies, each of the lay members must be either — (a) a person not subject to service law who is qualified for membership under paragraph (2) and not ineligible by virtue of rule 32; or (b) an officer or warrant officer who would be qualified for membership under section 156, and not ineligible by virtue of section 157 or rule 32, if this rule did not apply; and subsection 155(3) shall not apply in relation to the proceedings. (2) For proceedings to which this rule applies, a person not subject to service law is qualified for membership of the court unless — (a) he is aged under 18, or has reached the age of 70, at the commencement of the proceedings; (b) he is not a United Kingdom national; (c) he is a mentally disordered person; (d) he is disqualified for jury service; (e) he is a member of the Military Court Service; or (f) he is on the staff of the Service Prosecuting Authority. … (5) This rule applies to — (a) trial proceedings, if any defendant is not subject to service law at the commencement of the proceedings; …"