Mutual Legal Assistance

Mutual legal assistance (“MLA”) is the formal co-operation between sovereign states in criminal investigations and proceedings. It encompasses the provision of information and evidence to other jurisdictions, and making witnesses available to foreign trial courts. Although extradition can be seen as a form of MLA, normally it is considered as a separate legal process.

Historic MLA instruments

Historically, the United Kingdom was a party to numerous mutual legal assistance treaties (“MLATs”), conventions, protocols and framework decisions, implemented with a view to improving cooperation in such matters. The United Kingdom may also assist countries outside of such formal agreements.

UK MLA instruments operated at the level of the Council of Europe, the European Union (“EU”), the Commonwealth and the United Nations. The UK has additionally pursued MLA with other countries on a bilateral basis (a list of these can be found here).

The primary instruments that historically governed MLA included:

Within the Commonwealth, a majority of members adopted the Harare Scheme, which is of voluntary application.

However, 2017 heralded a major change to the MLA landscape in EU, through the introduction of Directive 2014/41/EU regarding the European Investigation Order (“EIO”) in criminal matters.

The EIO, which entered force in the UK from 31 July 2017, by virtue of the Criminal Justice (European Investigation Order) Regulations 2017 (“the UK Regulation”) and the Criminal Procedure (Amendment No 3) Rules 2017, and now operates between two thirds of all EU Member States, simplifies the existing legal framework for the gathering and transfer of evidence in one Member State for the use in another.

The EIO is designed to replace the following legal provisions from the pre-existing “patchwork” MLA scheme, outlined above:

  • European Convention of 1959, its Protocols and bilateral agreements concluded under it, as well as the EU Convention of 2000.
    Freezing Orders Framework Decision (2003/577/JHA).
  • The EIO also takes precedence over, inter alia, the Convention implementing the Schengen Agreement and the European Evidence Warrant Framework Decision (2008/978/JHA).


European Investigation Order


An EIO is a judicial decision which has been issued or validated by a judicial authority in an ‘issuing state’, which takes effect, and enables one or more specific investigative measures to be carried out, in the ‘executing state’.

EIOs operate to the principle of automatic mutual recognition, subject to certain (limited) prescribed grounds for refusal or non-recognition, and more than one EIO may be issued in the same investigation.

Directive, Articles 1 and 8 and Recitals 6 and 7

Types of proceedings

An EIO may be issued in the following types of proceedings:

  • with respect to criminal proceedings that are brought by, or that may be brought before, a judicial authority in respect of a criminal offence under the national law of the issuing State;
  • in proceedings brought by administrative authorities or judicial authorities in respect of acts which are punishable under the national law of the issuing State by virtue of being infringements of the rules of law and where the decision may give rise to proceedings before a court having jurisdiction, in particular, in criminal matters;
  • in connection with proceedings referred to, above, and which relate to offences or infringements for which a legal person (such as a company) may be held liable or punished in the issuing State.

Directive, Article 4

Types of investigative measure

The types of investigative measure available under an EIO encompass:
temporary transfer of a person who is already in the custody of the executing state, to the issuing state, to carry out an investigative measure (and vice versa). Note that where a person is to be transferred to another Member State for the purposes of prosecution, a EAW should still be issued in accordance with the EAW Framework Decision 2002/584/JHA. Further, under the UK Regulation, the power can only be used in respect of a UK prisoner in relation to a criminal investigation or criminal proceedings which are underway in the UK.

Directive, Articles 2-23; UK Regulation, Regs 20-22

  • hearing of the evidence of a person in the territory of the executing state by video conference, other audio-visual transmission and telephone conference;

Directive, Articles 24-25; UK Regulation, Regs 14(2), 36, 37 and Sch 6

  • measures to obtain details of bank and financial accounts and operations;

Directive, Articles 26-27; UK Regulation, Reg 15

  • real-time gathering of evidence including the monitoring of banking or other financial operations;

Directive, Article 28; UK Regulation, Reg 16

  • investigations into potential crimes committed by officers acting under covert or false identity (so-called ‘covert investigations’)

Directive, Article 29; UK Regulation, Reg 17

  • interception of telecommunications; and

Directive, Article 30; UK Regulation, Reg 19

  • “provisional measures” preventing the destruction, transformation, removal, transfer or disposal of an item that may be used as evidence.

Directive, Article 32; UK Regulation, Reg 18

In the UK Regulation, a court may make specific orders obtaining customer information or account monitoring orders as well as search warrants and production orders.

UK Regulation, Regs 43-44; 38-41; Criminal Procedure (Amendment No 3) Rules 2017).

The executing authority shall have, wherever possible, recourse to an investigative measure other than that provided for in the EIO where either: (i) the investigative measure indicated in the EIO does not exist under the law of the executing State; or (ii) the investigative measure indicated in the EIO would not be available in a similar domestic case.

Directive, Article 10(1)-(2)

Note that an EIO cannot be used for the setting up of a joint investigation team and the gathering of evidence within such a team, which are to be dealt with separately under existing instruments.

Directive, Article 3

Overview of EIO process

(i) Applying for an EIO
In the UK, an application for an EIO can be made, after an investigation is commenced, by a designated prosecuting authority or, with the consent of the prosecuting authority (or in Scotland by the Lord Advocate or prosecutor fiscal), a constable. The issuing of an EIO may also be requested by any party to proceedings that have already been instituted, including by a suspected or accused person, or by a lawyer on his behalf.

Directive, Article 12 (1) UK Regulation, Reg 6(3)

(ii) Issuing an EIO
EIOs may be then be issued by a judicial authority or designated public prosecutor (known as the “issuing authority” under the EIO regime). In the UK, a judicial authority will be a judge or justice of the peace. Designated public prosecutors include inter alia, the Director of Public Prosecutions, any Crown Prosecutor, and the Bank of England, Director of the Serious Fraud Office (SFO) and designated persons from the Financial Conduct Authority (FCA) and Prudential Regulation Authority (PRA).

UK Regulation, Reg 5(b) and (1) and Sch 1, Pt 1

In order for an EIO to be issued, the issuing authority must be satisfied that it is:

  • necessary and proportionate to make the order for the purposes of the investigation or proceedings in question;
  • the investigative measure to be specified in the order could lawfully have been ordered or undertaken under the same conditions in a similar domestic case (taking into account factors such as the nature of the evidence to be obtained, the circumstances in which the evidence exists, and the nature and seriousness of the offence); and
  • where the order is for an investigative measure in relation to which specific provision is made in Chapter 2 of the UK regulations (which covers videoconference and telephone hearings, banking/financial operations, covert investigations, telecommunication intercepts and those provisional measures, identified above), any conditions imposed by virtue of such provision are satisfied.

UK Regulation, Regs 6(4); 7(4); 11, 13-19

Further, to be authorised, an EIO must also meet the same requirements as that required for a similar investigative measure used in a domestic case.

UK Regulation, Regs 11(3), (4)

(iii) Transmission
The designated public authority, or, in prosecutor-initiated or prosecutor-approved EIOs, the prosecutor carrying out that action, is responsible for transmitting the EIO to the central authority or appropriate executing authority in the executing state. The judicial authority may be responsible for transmission where the EIO application is made by a party to proceedings that are in progress (and not the prosecutor or constable).

UK Regulation, Reg 9, Sch 1, Pt 2

(iv) Varying and revoking an EIO – outbound
An application to a court to vary or revoke an outbound EIO may be made at a hearing, pursuant to Criminal Procedure Rules (“CrimPR”) rule 47.61. The person who applied for the order, a prosecuting authority or a person affected by the order can apply to revoke or vary it. These proceedings are held in private unless the Court orders otherwise. The court may further rule that a hearing take place in the absence of the applicant, the respondent or other person affected by the order, subject to certain conditions.

CrimPR, rr 47.60, 47.61

The judicial authority or public prosecutor who has made or validated a EIO may also vary or revoke it on application of the person who applied for the order, a prosecuting authority (or in Scotland, the Lord Advocate or procurator fiscal) or any other person affected by the order.

UK Regulation, Reg 10; CrimPR r 18.25(3) and (4)

(v) Varying and revoking an EIO – inbound
Where a nominated UK court has given effect to an inbound EIO, for example by issuing a search warrant or production order, the Police force to whom the EIO was sent, a constable retaining the evidence in advance of transmission, the Lord Advocate or procurator fiscal(in Scotland), or any other person affected by the order may apply to vary or revoke it. However, when considering such an application, the nominated court must not entertain any challenge to the substantive reasons in relation to which the EIO was issued in the issuing state.

UK Regulation, Regs 41, 48

(vi) Format
EIOs are to be transmitted using a standardised format, with the template set out in Annex A of the Directive (see here).

(vii) Execution
Once the EIO has been issued and transmitted, it is recognised in the executing state without any further formality required, subject to those proscribed grounds for refusal, non-recognition and postponement, set out below (and so long as the EIO does not run counter to fundamental principles of law in the executing state). If under the law of the executing state the investigative measure sought does not exist, an alternative investigate measure should be used, where possible.

Directive, Article 9 & 10


The decision on the recognition and execution of an EIO, and the investigation measure underpinning it, should be carried out with the same “celerity and priority as for a domestic case”, subject to time limits.

Directive, Article 12 (1)

In general terms, those time limits are:

  • the executing authority and any designated central authority must acknowledge receipt of an EIO within 7 days;

Directive, Articles 7 and 16; UK Regulation, Reg 26 (3)

  • the executing authority take the decision to recognise or execute the EIO within 30 days of receipt, extendable by a maximum of 30 days where this is not practicable (this is extendable by 60 days in the UK); and

Directive, Articles 21(3), 12(5) and 16(5) 7 and 16; UK Regulation, Reg 30(1), 30(2)

  • the executing authority has 90 days after taking the decision to recognise and execute the EIO to carry out the investigative measure, which may be varied where this is “not practicable” and the central authority has notified and consulted with the issuing authority.

Directive, Article 12(4) and 12(6); UK Regulation, Reg 30(3) and 30(5)

Additionally, it is worth noting:

  • the executing authority must transmit ‘without undue delay’ information or evidence to the issuing authority that it already possesses; and in cases of urgency, expressed as such by the issuing authority, the executing authority must shorten the timescales as much as possible.

Directive, Article 12(2); Article 13(1); UK Regulation, Reg 30(7)


Prescribed grounds for refusal, non-recognition and postponement


Focusing on the UK Regulation, the executing state may, subject to a duty to consult with the issuing authority, refuse to execute an EIO on the following grounds:

  • execution would be impossible because of an immunity or privilege under the UK law, or law on freedom of press or expression;
  • execution would harm national security interests, jeopardise a source of information, or involve the use of classified information relating to intelligence activities;
  • in proceedings brought by judicial or administrative authorities in cases pertaining to rule of law issues (which may give rise to criminal matters), the measure would not be authorised under the law of the executing state in a similar domestic case;
  • execution would run counter to the principle of ne bis in idem (double jeopardy);
  • the EIO relates to a criminal offence which is alleged to have been committed outside the territory of the issuing state and wholly or partially in the UK, and the conduct does not constitute an offence under the criminal law of the UK;
  • there are substantial grounds for believing that the EIO would run counter to European Convention of Human Rights (within the meaning of the Human Rights Act 1998), or has been issued on the basis of, for example, grounds of sex, race, religion or political opinion, or an individual might be prejudiced through investigations or proceedings that are predicated on those characteristics.

UK Regulation, Sch 4

Equally, refusal can be justified (subject to certain exceptions) where:

  • unless the EIO pertains to evidence which is already in the possession of the executing authority, or which is in directly accessible databases held by police or judicial authorities, and if the investigative measure indicated in the EIO does not exist under the law of the relevant part of the UK, and it appears to the central authority that there is no other investigative measure which would achieve the same result;
  • the investigative measure would not be available in a similar domestic case, and it appears to the central authority that there is no other investigative measure which would achieve the same result;
  • the conduct in relation to which the EIO has been issued does not constitute an offence in the UK and does not fall within the offences set out in Annex D to the Directive, punishable in the issuing state with imprisonment/other form of detention for a three-year maximum term;
  • the use of the investigative measure sought in the EIO is restricted in the UK to a list of offences punishable by a specific threshold, which is not met.

Further certain refusal grounds exist in relation to where the EIO is requested for covert operations, real-time/intercept evidence and videoconferences.

UK Regulation, r 28(1)(f)-28(1)(k)


Execution of an EIO may be postponed where execution of the EIO might prejudice an ongoing criminal investigation or prosecution, or where the information sought is already being used in other proceedings.

UK Regulation, r 29(2)