s 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— (a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (b) no lay members. (2A) In the case of proceedings where the number of lay members would (but for 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. (6A) Court Martial rules may provide that in prescribed circumstances the Court Martial is to remain validly constituted despite the reduction of the number of lay members— (a) from six to five, or (b) where a direction has been made under subsection (2A), from four to three, if a judge advocate gives a direction to that effect. (7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (9) In this section— “ OR-7 rank ” means any of the following— chief petty officer; staff corporal; staff sergeant; colour sergeant, Royal Marines; flight sergeant; chief technician; “ prescribed ” means prescribed by Court Martial rules.