1.1 Informal International Cooperation

Informal international cooperation in criminal matters can take several forms: police-to-police, or agency-to-agency. This assistance may occur at any stage of a criminal investigation but usually before, or in parallel to, formal cooperation.

Police-to-police and other agency-to-agency assistance can be an effective way to determine what material is held by a foreign country prior to making a mutual assistance request (MAR). Informal cooperation may not be subject to specific legislative frameworks, but can be governed by policy and practice, often on the basis of reciprocity.

There are many agencies involved in the sharing of information through informal assistance.

Police-to-Police Assistance

Police-to-police assistance is a form of cooperation between police in one country and police in another country. Police-to-police assistance is often used at the early investigation stage or to obtain evidence that does not require the use of coercive powers or the provision of a MAR. Evidence provided on a police-to police basis generally cannot be admitted into evidence in criminal prosecutions.

  • e.g. Exchange of intelligence information.
  • e.g. Preliminary enquiries to determine whether evidence of an offence is located in a foreign country.
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Agency-to-Agency Assistance

Agency-to-agency assistance is a form of cooperation between non-police agencies, such as financial intelligence agencies. For example, the Australian Transaction Reports and Analysis Centre (AUSTRAC), the Cook Islands Financial Intelligence Unit (CIFIU) and the Fiji Financial Intelligence Unit (FIU)) have information sharing arrangements with their counterparts in foreign countries. The information sought through agency-to-agency assistance often does not require a MAR.

1.2 Formal International Cooperation

Formal international cooperation in criminal matters generally occurs between the governments of two or more countries and can include:

Formal cooperation is governed by national legislation and bilateral or multilateral treaties and involves formal diplomatic and/or judicial functions. These mechanisms are highly effective tools for combating transnational crime, ensuring that an offender, or evidence of an offence, can be pursued despite being in a foreign jurisdiction.


Extradition is the formal, government-to-government process used to return people to another jurisdiction to either face prosecution for a criminal offence, or to serve a sentence of imprisonment for a crime for which they have already been convicted in that jurisdiction.  Extradition is an administrative, not criminal, process that is initiated at the request of a foreign government. The requested country must have a legal basis on which to accept the extradition request. The country’s domestic laws alone might allow a request to be accepted, or  there might need to be a bilateral extradition treaty, or a multilateral treaty with extradition obligations in place between the two countries.

Two key principles that underlie a successful extradition request from one country to another are dual criminality and speciality.

While an extradition request may be granted for serious criminal offences, there are some important  bars (or grounds of refusal) that each requested country must consider. Such bars include a request for extradition for an alleged political offence, military offence, an ulterior purpose, or the risk of prejudice   at trial. If an extradition request relates to an offence that concerns one of these bars, the request will normally be considered by a Minister or judicial officer of the requested country to determine if the request can be accepted. Another important bar to extradition is double jeopardy.

Usually, a requested country’s laws will set out a number of mandatory requirements that must be met before a requested country can accept an extradition request. These requirements may be supplemented by requirements contained in a bilateral or multilateral treaty.

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Extradition is not deportation. It is a government-to-government process for achieving criminal justice purposes initiated by formal request and includes human rights safeguards to protect people (e.g. an extradition request may be rejected where there is the risk of the death penalty, torture, cruel, inhuman or degrading treatment). Unlike extradition, deportation is a unilateral determination made by a country to remove a person on the basis that they have no right to be in that country for immigration purposes. Depending on domestic law and procedure, some countries make a distinction between these processes in regard to a criminal prosecution. That is, there may be ramifications for a prosecution if a requested country deports rather than extradites a person wanted for a criminal justice purpose.

Mutual Legal Assistance (MLA)

MLA is the formal government-to-government process to obtain international assistance in criminal investigations, prosecutions, and to recover proceeds of crime. MLA is generally used for obtaining material that cannot be obtained through informal international cooperation mechanisms. It generally involves the provision of evidence that will be relied upon in court as part of a criminal prosecution.

More detailed information is provided in chapters 3, 4, and 5.

International Transfer of Sentenced Prisoners

Another specialised and growing area of international cooperation between countries is the international transfer of sentenced prisoners. This is where arrangements can be made between countries to transfer persons sentenced to terms of imprisonment in one country so that they serve their sentences in their country of citizenship.

1.3 Legal Bases for International Cooperation in Criminal Matters


International cooperation in criminal matters can be effected on the basis of a bilateral treaty on MLA, or on the basis of a multilateral treaty that deals with other subject matter but contains MLA obligations on the parties to the treaty. Examples of such multilateral treaties include:

Domestic Law

Where no treaty exists between countries for the purpose of international cooperation in criminal matters, the domestic law of a country may provide a basis for cooperation. Civil law is the most prevalent legal system found around the world and is premised on the system of codification of laws. Common law is the second most prevalent legal system and it is premised on the law being developed through jurisprudence of the courts. Common law jurisdictions are typically found in Commonwealth countries of the former British Empire. Domestic law is often used as the primary basis for cooperation in common law legal systems.

The distinction between civil law and common law becomes very apparent at the evidence gathering stage. In civil law systems, a magistrate gathers the evidence and no rules of evidence bar admissibility. In common law systems, a law enforcement investigator gathers the evidence and there are usually many evidentiary rules that affect all aspects of an investigation.


The principle of reciprocity, also known as ‘comity’, is a long established principle in the relations of countries with respect to matters of international law and diplomacy. The principle of reciprocity means that where one country requests assistance or cooperation from another, that second country is generally expected to provide future similar assistance or cooperation, to the fullest extent permitted under its domestic law, to the first country in the in respect of equivalent criminal offences.

This principle is usually incorporated into treaties, memoranda of understanding and domestic   law. Reciprocity is particularly prevalent in states with a civil law tradition, where it is viewed as a binding covenant. In common law countries, it is not viewed as an obligatory principle.

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Reciprocity can also be a useful tool in the absence of a treaty, as it can be taken to be as a stand-alone promise that one country will do the same for another country in the future should the need arise.

1.4 Key Principles of International Cooperation

Dual Criminality

The dual criminality (or double criminality) principle requires that the conduct which is the subject of the request for international cooperation must be criminal in both the requesting and recipient country. This is often assessed at the time a request is received from a foreign country. Countries are required to treat this requirement as being fulfilled if the conduct underlying the offence is criminalised in both countries, irrespective of whether the countries attach the same kinds of legal nomenclature to the offence in their domestic laws. This principle reflects the fact that the bulk of MLA and extradition between countries still takes place via bilateral treaties and seeks to limit the artificial restrictions based on domestic law that would counteract international cooperation.

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Double Jeopardy

Double jeopardy (non bis in idem or ne bis in idem) is a procedural defence that prevents an accused person from being tried twice on the same charges or another charge constituted by the same conduct following a valid acquittal or conviction. The recipient country may refuse assistance when it is clear that an accused has already been convicted and, for extradition, undergone punishment or acquitted for the same offence or another charge constitute by the same conduct set out in the request.


The confidentiality principle requires that any information shared by the requesting country in a request, including communications between central authorities about the request, will be treated as confidential by the receiving state. This is recognition of the general understanding and expectation of confidentiality that is expected between countries in the mutual assistance process. Using this information without the requesting country’s agreement or after consultation of the requesting country may seriously harm the criminal investigation, national security or international relations.



The speciality principle requires that a person may only be prosecuted, or serve a sentence, for the offences in relation to which the request for international cooperation is granted. For example, if Country A provides Country B with evidence about a person in relation to one offence, that evidence cannot be used to prosecute that person, or any other person, in relation to another offence unless Country B seeks the permission of Country A to use the material for alternative purposes, and Country A specifically agrees.