(a) Investigations and summary disposals;

(b) Trials by court-martial;

(c) Reviews by reviewing authorities; and

(d) Appeals to the Courts Martial Appeal Court.

The military justice system traces its roots, through its British military heritage, to Roman law. However, the modern system is derived from two Acts of Parliament: the Armed Forces Discipline Act 1971 ("AFDA") and the Courts Martial Appeals Act 1953. A further important source of military law is subordinate legislation made under the authority, in the main, of the AFDA. The two most important of these sources are the Armed Forces Discipline Rules of Procedure 1983 and the Defence Force Orders (Discipline), which replaced earlier Defence Council Orders in 1997. Collectively, this legislation provides for a common code (subject to some slight variations between the Navy and the Army/Air Force) for the maintenance of discipline and the administration of justice in each of New Zealand's three armed services.

This code has extra-territorial effect, which means that members of the Armed Forces take New Zealand military law with them wherever in the world they go. The military justice system also operates side by side with New Zealand's criminal justice system, which means that the Armed Forces have concurrent jurisdiction with the NZ law enforcement authorities over any offence committed by a member of the Armed Forces within New Zealand.

In common with New Zealand's criminal justice system, persons charged under military law have the right to be presumed innocent until proven guilty. Proof means proof beyond reasonable doubt. The law of evidence which applies in New Zealand's criminal courts also applies before its military tribunals, subject to some limited special rules which take account of the military context.

All the legal materials which underpin New Zealand's military justice system are to be found in the two volume Defence Force publication, the Manual of Armed Forces Law, also known as DM 69. DM 69 is an invaluable reference for anyone seeking to understand the military justice system and, as well as being widely distributed within the Armed Forces, is held by all major District Law Society libraries and university law libraries within New Zealand.

In contrast with the prosecutorial discretion conferred on the NZ Police, whenever an allegation is made that a person subject to the AFDA (in the main, members of the Armed Forces) has committed an offence, that person's commanding officer is required, unless he or she does not consider the allegation well-founded, to either cause the person to be charged or refer the matter to the appropriate civil authority - usually the civilian police. (See section 103 of the AFDA.)

Once a charge has been laid under the AFDA (including offences against the ordinary criminal law of New Zealand, which are also offences contrary to section 74(1) of the AFDA), a formal investigation is conducted by the appropriate summary authority (depending on the rank and service of the accused, among other things). This is an inquisitorial hearing to determine whether there is a prima facie case. If the officer hearing the charge finds that there is a prima facie case, he or she will then take the necessary steps to bring it before the appropriate military tribunal. In some cases, because of the rank of the accused or the nature of the offence alleged, this must be a court-martial. In most cases, the charge can be tried (Navy) or dealt with by an officer exercising summary powers. This officer might be, for example, the accused's commanding officer, executive officer (Navy), detachment commander, a subordinate commander (Army/Air Force) or a superior commander, depending on the rank and service of the accused.

In some cases, where the charge is to be tried or dealt with by the accused's CO, because of the seriousness of the charge and the gravity of the punishment which the CO would need to impose if the accused were found guilty, the CO must offer the accused the right to elect trial by court-martial and may only try or deal with the charge if the accused does not wish to take up the offer.

There are two types of courts-martial under NZ military law: restricted courts-martial and general courts-martial. A general court-martial has the full sentencing powers of the High Court of New Zealand (the most severe penalty being life imprisonment), whereas a restricted court-martial may only impose a maximum of 2 years' imprisonment.

A trial by court-martial will only be held after the accused's commanding officer has heard the charge or charges and decided that there is a prima facie case. Where the commanding officer has so found, and the circumstances dictate (for the reasons indicated below, among others) that the matter should be tried by a court-martial, the commanding officer will order the preparation of a summary of evidence (Army/Air Force) or abstract of evidence (Navy), which have a similiar function to depositions in a civilian trial. When the summary or abstract has been completed, the commanding officer will ensure that the charge sheet is properly drawn and then make a formal application to the convening officer for the convening of a court-martial to try the charge or charges.

The convening officer, who is usually the accused's superior commander, will generally hold a warrant from the Chief of Defence Force or the Chief of Staff of his or her Service to convene courts-martial. The convening officer has the final decision as to whether or not a court-martial is justified on the evidence and, if so, what charges should be preferred. In making these decisions, NZ military law requires that the convening officer be advised by a legal staff officer.

Courts-martial are generally reserved for the more serious cases, where an officer exercising summary powers would not have sufficient powers of punishment to deal with the offence if the accused were found guilty. If an officer is to be tried by a court-martial, that court must be a general court-martial. Furthermore, a general court-martial is the only military tribunal which can try an officer of or above the rank of Lieutenant Commander, Major or Squadron Leader.

Courts-martial are comprised of either 3 (restricted) or 5 (general) officers, one of whom is appointed the president of the court. These officers are appointed by the convening officer. Matters of evidence and procedure are the province of a judge advocate, appointed by the Judge Advocate General, who gives the court-martial directions on these matters which they must follow. In this respect, a trial by court-martial has similarities to a civilian jury trial.

In New Zealand, the Judge Advocate General is wholly independent of the NZDF, holding a warrant of appointment from the Governor-General. The judge advocates are similarly independent and, although they generally have military backgrounds, they are not members of the Armed Forces. Over half are currently District Court judges in their own right.

Whenever an accused person is found guilty by an officer exercising summary powers or convicted by a court-martial, that person's case is reviewed by a reviewing authority. The only exception to this is that certain cases involving very minor summary punishments do not have to be reviewed. Summary disposals are reviewed by the superior commander under whose command the case was tried or dealt with. Courts-martial are reviewed by the Board of Review, which consists of one-star officers from each service, advised by the Judge Advocate General or his or her deputy.

In addition, if a person so convicted or found guilty wishes to challenge the validity of his or her conviction or punishment, this may be done by way of an application for review (summary disposals) or petition (courts-martial) to the reviewing authority.

Any person convicted by a court-martial may lodge an appeal against his or her conviction in the Courts Martial Appeal Court. This is a superior court of record established under the Courts Martial Appeals Act 1953. The judges of the Courts Martial Appeal Court consist of all the judges of the High Court of New Zealand, together with any judges specially appointed to the court by the Governor-General in Council. These latter "appointed judges" generally bring considerable military as well as legal experience to the court, to better equip it to operate as a specialist court of military law.

The Courts Martial Appeal Court generally sits as a bench of three judges: one High Court judge, assigned to preside in a particular appeal by the Chief Justice of New Zealand, and two appointed judges. Three judges is the minimum number for a bench of the Courts Martial Appeal Court, but any other greater uneven number is permissible. Combinations of judges other than that outlined above (eg two High Court judges plus one appointed judge) are not unknown.

Appeals to the Courts Martial Appeal Court are generally final, however either the appellant or the Crown may lodge a further appeal to the New Zealand Court of Appeal if the Attorney-General certifies that the decision of the Courts Martial Appeal Court "involves a point of law of exceptional public importance and that it is desirable in the public interest that a further appeal be brought". (See section 10 of the Courts Martial Appeals Act.)