European investigations

Increasing cross-border mobility means that many homicide and serious crime investigations involve enquiries in one or more countries. To work with European partners and support an investigation, officers need to understand the policing and legal systems in other countries.

Officers may become involved in such investigations in a number of ways, for example:

  • an investigation into one or more incidents committed in the UK which involve a victim
    and/or offender located abroad, or may be linked to other crimes committed abroad
  • a UK citizen becoming the victim of serious crime while abroad
  • a request received for information or assistance from investigators in another country.

Investigators may also be involved in working to support the extradition of a suspect.

Suspect extradition

Extradition is the formal procedure for returning persons located in one country to another, for one of the following reasons only:

  • prosecution
  • to be sentenced for offences for which they have been convicted
  • to carry out a sentence that has already been imposed.

The extradition of a person to the UK is called import extradition or outgoing request. The extradition of a person from the UK is called export extradition or incoming request. An extradition request cannot be made for securing the return of a person for questioning. Within the EU, the European arrest warrant provides an efficient and streamlined extradition system.

UK prosecutions

Investigators may liaise with foreign law enforcement agencies (LEAs) in order to gather information, intelligence and evidence to support a UK prosecution of a foreign national. Those  involved include:

  • International Liaison Officer (ILO)
  • Crown Prosecution Service (CPS)
  • SIO
  • National Police Coordination Centre (NPoCC)
  • NCA liaison officers
  • Europol
  • ACPO criminal records office (ACRO).

Gathering information and intelligence

The process for requesting information or intelligence from a foreign LEA is known as police-to-police enquiries.

Evidence collection

Mutual legal assistance is the formal way in which countries request and provide assistance to obtain evidence. The request is made through a letter rogatory (commission rogatoire) or letter of request (also referred to as an international letter of request).


The ILO acts as a central point of contact and conduit for all incoming and outgoing international enquiries. In most forces the ILO is located in the force intelligence unit or equivalent HQ department and may only be available during normal office hours. For assistance outside office hours, investigators should contact the National Crime Agency (NCA) international desk.

Working with the ILO

Investigators should consider the following:

  • Approach the ILO as early as possible to explain and discuss requirements.
  • Be willing to listen to alternative and possibly more effective ideas.
  • Ensure that all reports going abroad are free of police jargon and written in plain English.
  • If enquiries are urgent, make sure that the ILO fully understands why.
  • Complete all parts of all forms submitted to the ILO as accurately as possible, making sure that any 5x5x5 grading is carefully completed to prevent requests being rejected or returned. For further detail see dissemination of intelligence.
  • Understand that what may appear ‘normal’ in an investigation based in England, Wales or Northern Ireland may not necessarily be normal practice in another state. A short explanation may be required.
  • Understand that it may not be possible for the ILO to say how long a request will take to action. Some states are inundated with requests on a daily basis and investigators must be patient.
  • Do not submit all requests as urgent. Doing so may place significant pressure on a requested state as not all EU member states have the same policing structure as England, Wales or Northern Ireland.
International enquiries

The ILO will provide advice and guidance on conducting international enquiries, and act as the force central contact point for NCA, Europol and INTERPOL. In addition, they should:

  • work with investigators to understand expectations and realities when conducting international investigations or enquiries
  • request conviction histories for all prisoners
  • disseminate relevant material and guidance throughout the force
  • identify specific crime scene marks and liaise with foreign law enforcement agencies to establish identification
  • identify details relating to wanted and missing persons
  • carry out proactive enquiries in line with force priorities and developing issues
  • liaise with divisional intelligence teams to help identify future concerns
  • continually review their role to monitor further positive interaction with internal departments and outside agencies
  • assist with missing persons enquiries with an international link
  • assist with the completion of risk assessments
  • on occasion work with foreign law enforcement community officers who may be able to pass on urgent disseminations to their country when the NCA/INTERPOL channels may not be swift enough. These are police and customs officers posted to the various embassies in the UK and are an invaluable source of support and assistance.


The CPS is a designated prosecuting authority under the Crime (International Co-operation) Act 2003 (CICA). Every case the CPS deals with is allocated to a reviewing lawyer who is responsible for all aspects of the file, including the issue of letters of request (LOR) and extradition requests.

Early consultation with the CPS is required due to the timescales involved in producing the LOR, particularly in cases where arrest warrants are involved.

Note: some European countries may be very specific on the way information is requested. The Netherlands, for example, has strict privacy laws which subsequently mean that they require an LOR for almost any request for personal data. Investigators should provide the CPS with robust reasons why an LOR is needed.

Contact details for CPS regional offices can be found on the CPS website.

Note: Northern Ireland has a separate Public Prosecution Service.


In the UK SIOs manage investigations from start to finish, including issues relating to international media interest, foreign victims, foreign family members and cooperation with international and domestic LEAs.

SIOs must, however, respect the intentions and processes in other foreign states and within all LEAs. They must always contact the foreign LEA via the ILO and NCA international. Direct contact may undermine effective working relationships, and in some cases be contrary to local laws.

Where an investigation attracts the attention of national or foreign media, input from senior police staff or a more intensive response may be necessary on a regional or national basis.

National Police Coordination Centre

In a complex investigation requiring a nationally coordinated response, the senior officer in charge should consider liaising with NPoCC as soon as possible.

NPoCC can advise on national policing responses and provide access to the ACPO president, who will be able to arrange any multi-agency involvement where necessary.

NCA liaison officers

NCA liaison officers are located in key locations around the world to help support the investigation of serious and organised crime which crosses international borders. The force ILO can contact NCA international to obtain advice on how to contact NCA liaison officers.

The role of the SLO is to generate and develop relationships with overseas law enforcement agencies in the state in which they are based. They are tasked by the NCA intervention planning teams to help with post-arrest plans. In certain circumstances, they may also be willing to assist with the transfer of police-to-police requests by providing local advice, establishing an appropriate point of contact and facilitating cooperation.

Their main responsibilities include:

  • collecting and reporting intelligence from overseas sources for the knowledge requirements of NCA
  • planning and executing intervention activity overseas in support of NCA’s tasked operations
  • supporting the business interests of other relevant NCA departments including enforcement, covert human intelligence source, proceeds of crime, and technical collection, within an overall programme that balances these interests with the primary goals of collecting knowledge and supporting tasked operations
  • operating a management and control system set out by the intervention planning teams in England, Wales or Northern Ireland
  • developing and sustaining an effective operational capability overseas.


With 190 member countries, INTERPOL is the world’s largest international police organisation. It facilitates cross-border police cooperation, and supports and assists all agencies, authorities and services whose mission is to prevent or combat crime. It has identified four core functions on which it concentrates its efforts and resources.

  • Secure global police communications services – I-24/7 enables authorised law enforcement users in all of its member countries to request, submit and access critical police data instantly in a secure environment. Foreign nationals brought into custody should be processed through I-24/7 to identify those suspects who may be wanted by foreign states. Unless they are known to be in the UK, there will be no entry on the PNC.
  • Operational data services and databases for the police – INTERPOL maintains databases covering key data such as names of suspected terrorists, child sexual exploitation images, fingerprints, DNA profiles, stolen or lost identification and travel documents, and wanted persons.
  • Operational police support services – INTERPOL focuses resources on six priority crime areas: corruption, drugs and organised crime, financial and hi-tech crime, fugitives, public safety and terrorism, and trafficking in human beings.
  • Police training and development – specialist police training initiatives for national police forces, and on-demand advice, guidance and support in building dedicated crime-fighting components are provided to help member countries combat serious transnational crime and terrorism. This includes sharing knowledge, skills and best practice in policing, and the establishment of global standards for combating specific crimes.


This is the EU law enforcement organisation that handles criminal intelligence. Its aim is to improve the effectiveness and cooperation between the competent authorities of the member states in preventing and combating serious international crime and terrorism.

Europol‘s mission is to make a significant contribution to EU law enforcement action against organised crime and terrorism, with an emphasis on targeting criminal organisations. To support this Europol hosts the Europol information system (EIS).

Each member state has a European national unit (ENU), usually situated in the headquarters of the national law enforcement agency. The UK ENU is NCA international, and it supports the UK Europol liaison officers. It is through these units and agencies that all intelligence between the UK and Europol flows. For further information see NCA working in partnership worldwide.

Europol information System

The Europol Information System (EIS) is hosted at Europol’s HQ in the Hague. It is available to LEAs within the EU.

The main objective of the EIS is to support Europol and EU member states to fight terrorism, drug trafficking and other forms of serious cross-border organised crime. The EIS provides the facility for storing, searching, analysing and displaying information related to transnational crimes, allowing law enforcement agencies across Europe to collaborate efficiently in their investigations.

The system supports automatic detection of possible hits between different investigations and facilitates the sharing of sensitive information in a secure and reliable way. The data entered onto the EIS remains under the full control of the owning member state. Another member state or Europol cannot alter it in any way.

Every search result can only be disseminated and/or used in compliance with the handling codes, to ensure that the processing of information is carried out in line with the wishes and legal framework of the owners of the information. The UK can, and does, restrict the access to its data where there is an operational requirement or other sensitivity.


The ACPO Criminal Records Office (ACRO) offers a number of services to police officers and staff when investigating foreign nationals.

ACRO’s international portfolio is dedicated to exchanging criminal conviction information between the UK and other countries within the European Union (EU) and around the world. Criminal conviction exchange between EU member states is governed by an EU framework agreement. ACRO acts as the UK Central Authority for this exchange and supports UK law enforcement by:

  • submitting requests to obtain extracts from EU criminal registers for a person who is being investigated, arrested or managed by UK police forces and authorised agencies. Requests can also be made for victims and witnesses.
  • receiving notifications of convictions handed down against UK nationals in other EU member states and updating UK registers, including the PNC, with such convictions.
  • notifying relevant member states of any convictions (and updates to previous convictions) imposed in the UK on a national from that EU member state.

Criminal conviction exchange with countries outside the EU is conducted using the INTERPOL channels of communication (I-24/7). ACRO conducts this exchange and supports UK law enforcement by:

  • submitting requests to check for criminal convictions in countries outside the EU for persons subject to various proceedings in the UK, mainly criminal proceedings. Requests can also be made for victims and witnesses.
  • receiving notifications of convictions handed down against UK nationals in a limited number of countries and updating UK registers, including the PNC, with such convictions.
  • notifying relevant countries of any convictions (and updates to previous convictions) imposed in the UK on a national from that country.

Police officers and police staff are advised to make a request via ACRO for foreign conviction checks in all cases where the suspect, defendant, victim or witness is a foreign national. The ACRO International Criminal Conviction Exchange Request form should be completed and submitted either to [email protected] or via a force international liaison officer/team – in accordance with local force procedures.

For further information on the process of submitting a request, the specific data requirements for each country and a full list of FAQs, visit the International Criminal Conviction Exchange community on the Police Online Knowledge Area (POLKA). This link is available to authorised users who are logged on to POLKA.

Where appropriate and possible, ACRO matches the conviction data of UK nationals who have offended overseas to equivalent, recordable offences in England and Wales and updates the PNC accordingly. If a link to Scotland or Northern Ireland is identified, the information is disseminated to the appropriate agencies.

Conviction information for non-UK nationals received as the result of an outbound request to an EU member state can be used only for the purposes for which it was requested. This stipulation prevents the PNC from being updated, unless the conviction represents an immediate and serious threat to public security. Offences which fulfil these criteria are included in a list of offences known as the Home Office Serious Offence List. These offences are added to the PNC by ACRO.

Under section 103 of the Criminal Justice Act 2003, all convictions held overseas have the same relevance, in relation to evidence of bad character, as those committed in England, Wales and Northern Ireland.  Officers should liaise with the CPS at the earliest opportunity if foreign previous convictions are to be used in criminal proceedings, to ensure that relevant documentation is obtained.

Police-to-police enquiries

Enquiries may relate to tracing vehicles, suspects, victims or witnesses, or to checking bank account details. In all cases investigators must first contact the force ILO for advice and assistance.

Police-to-police enquiries can be a useful research tool for a mutual legal assistance request.

All police-to-police enquiries should be submitted on an INTERPOL enquiry form (NCA form 1) via the ILO to NCA international. NCA form C (risk assessment) should also be completed and forwarded to the ILO for onward transmission. Some forces, however, may have existing agreements in place via other channels.

The Swedish initiative sets out the rules for cross-border exchanges of criminal information and intelligence. Under this initiative, there are strict time limits and conditions that competent law enforcement authorities, including the police, must adhere to when they receive a request for information and intelligence.


Some intelligence can be submitted to Europe without an inspector’s authority. If the intelligence has a handling code of ‘1’, it can be sent to any EU or European economic area country.

A risk assessment authorised by an inspector is required for intelligence disseminations involving sex offenders or areas of risk. Outside Europe, all enquiries require a risk assessment authorised by a superintendent.

When gathering information, intelligence and evidence, investigators need to be aware of data protection issues. They may also be required to travel abroad in connection with an investigation.

Data protection

Data protection rules vary across Europe. However, the Council Framework Decision 2008/977/JHA on the protection of personal data processed via police and judicial cooperation on criminal matters provides a minimum appropriate standard of data protection where personal data is exchanged between EU member state LEAs.

Investigators need to understand that several EU agreements have their own data protection rules. These set out the limitations for use of the data supplied under that agreement.

When considering whether to share personal data with third-party states outside the EU, investigators need to consider whether additional data protection safeguards should be established.

Advice must be sought where investigators intend to share personal data with non-EU states that retain the death penalty or have a poor human rights record.

All disseminations should be sent with an attached risk assessment. For further detail on the different levels of authority needed prior to dissemination, see dissemination.

Investigators should also contact their force data protection representative for further information.

Overseas deployment

To travel abroad in support of a UK investigation, a police officer should first seek the authority of their chief constable or equivalent.

NCA international must be contacted before a police officer travels abroad for operational reasons in support of a UK investigation. A UK investigation may have links with other international crime enquiries, including organised crime. The presence of UK police officers abroad could jeopardise an ongoing European investigation and in some cases put officers at risk.

SLOs have networks with police forces in most countries. They can give advice and arrange contact with the most appropriate overseas department to assist with a request for a police officer to travel abroad.

For further information on the process for requesting authorisation to travel abroad, contact the international police assistance section of the Home Office.

In addition, the police federation and relevant unions have policies and procedures in place to manage potential health and safety risks for officers travelling abroad.

Mutual legal assistance

Mutual legal assistance (MLA) is the formal way in which countries request and provide evidence located in one country to assist in criminal investigations or proceedings in another country.

In England, Wales or Northern Ireland, MLA requests are made via an LOR (also known as an international letter of request (ILOR)). The purpose of an LOR is to ask the requested state to obtain specific, identifiable evidence.

An LOR outlines the case, the evidence requested and any legislation that should be adhered to in order to ensure that the evidence is gathered in a way that will be admissible in the requesting state’s proceedings.

Responsibility for drafting and issuing an LOR rests with the relevant prosecution authority. In the UK this is the CPS.

MLA can be a resource intensive and time-consuming process, placing considerable burdens on the requested state. It should, therefore, be used only where the evidence is necessary and expected to add value. It must not be used if material can be obtained through other means, eg, where material is already in the public domain.

Letter of request

Evidence can be requested both before and after a person is charged with an offence. During the investigation phase, an LOR can be issued even prior to any suspect being arrested.

Types of assistance that can be provided under an LOR include a request:

  • to take witness statements
  • to search and/or seize property
  • to formally interview suspects
  • for banking evidence
  • for telecommunications data
  • to allow UK personnel to travel to the overseas state in question in order to conduct enquiries
  • to conduct covert deployments.
European Investigation Order

The European Investigation Order (EIO) comes into effect in the UK on 31 July 2017. See European Investigation Order for further detail.

Collecting a suspect from abroad

Usually, an agreement between the police force of England, Wales or Northern Ireland and the requested country is required, detailing how and when the suspect will be collected and transported back to the requesting country.

Once the hearing has taken place in the country where the subject has been arrested, and the decision has been made to agree extradition, there is usually a ten-day period during which time the subject must be collected.

Within this ten-day period, the suspect has the right of appeal up to seven days after the date of the hearing.

In this timeframe, NCA makes the initial notification to the force. It may be a day or two before the collecting force is made aware of the situation. It is advisable that close contact is maintained with NCA from the time of arrest until the travel plans have been confirmed.

Officers collecting the suspect need to submit provisional travel plans to NCA. NCA then liaises with the relevant agency abroad to complete negotiations and confirm the collection plans.

There are a number of practical considerations officers should be aware of before collecting suspects. These include the availability of flights, risk assessments and multi-agency communication.

Key steps

There are a number of key steps that should be followed when collecting a suspect from abroad:

  • INTERPOL notifies the ILO of extradition
  • the ILO liaises with appropriately trained officers (usually three) and plans an outline date to travel
  • arrange flights via local force procurement
  • complete risk assessment for airline
  • provide all details to INTERPOL so that arrangements can be made with the foreign state, and confirm time, date and location of exchange
  • arrange for letter of introduction and provide copy of documentation to travelling officers
  • collect subject and return.

Foreign prosecutions

Police forces in England, Wales and Northern Ireland can assist a foreign jurisdiction by gathering information, intelligence or evidence in the UK on behalf of the requesting nation, or by being deployed overseas.

Requests for evidential material are made to the UK using an LOR via the UK central authority (UKCA-mutual legal assistance).

It is important to understand the various justice systems applicable to an investigation in a foreign jurisdiction, and for the investigator to be aware of potential differences to the UK. See also the legal framework.

Note: it is not uncommon for foreign law enforcement officers to make direct contact with UK police. Care must be taken when sharing intelligence and information this way as, once released, it is impossible to control.

Death of a British national abroad

Where a British national dies abroad in suspicious or violent circumstances, the investigation is conducted by the appropriate authority in the foreign jurisdiction. The UK police may be involved in providing assistance abroad.

There are, however, limitations to the support that UK law enforcement can supply.

Potential differences

There are a number of ways in which a foreign justice system may differ.

  • Detention laws, eg, in certain EU member states detention of a suspect allows for an interview to be undertaken, even in instances where the interviewing officers do not know  not all the facts.
  • Police staff and members of foreign LEAs may not be willing or readily understand the need to provide written statements for their part in an investigation. Instead, the prosecutor presents any evidence to the court.
  • A statement may be a police officer’s account of an interview they had with a victim or witness.
  • The role of family liaison officer (FLO) does not formally exist in many countries.
  • Mediums or psychics may be used as part of an investigation.
  • Community policing may not exist or have the same importance as it does in England, Wales or Northern Ireland.
  • There may be a lack of understanding of the need for additional and formal enquiries to be carried out once a suspect has made an admission of guilt.
  • The prosecutor may make the arrest as the police may only have the power to detain.
  • Crisis teams or other groups may be used to represent and assist national citizens when overseas should they become a victim of a serious crime, or are caught up in a disaster or accident. See ACPO (2012) Practice Advice on European Cross-Border Investigations, section 4.3 Working with Foreign Crisis Teams and Official Groups.

Providing assistance abroad

There are limited circumstances in which a UK police officer would is required to conduct enquiries abroad. In the majority of cases, the UK police will merely assist foreign police with an ongoing investigation.

UK police officers travelling abroad do so at the invitation, and with the permission, of the requesting state. Officers visiting another state have the same status as a member of the public. They have no jurisdiction while abroad. This is no different from when a foreign law enforcement officer visits the UK.


Cross-border investigations can have varied resource implications for forces because:

  • different jurisdictions have differing needs (eg, the method of dealing with or processing requests for information)
  • the unique circumstances of each case requires different levels of response
  • there is a difference in the requirements of individual victims and their families
  • different forces have differing capacities and priorities to provide assistance.

As every case is different, each must be assessed on its own merits and resourced proportionately, according to its needs.

In the majority of cases, however, requests from foreign jurisdictions are straightforward and do not require vast amounts of resources.

Joint investigations

A joint investigation team (JIT) is a team made up of representatives from two or more EU member states’ competent authorities, for a specific purpose and for a limited period of time. The JIT is based on an agreement between the parties. Although non-EU member states are not able to establish a JIT, they may participate if all other parties agree.

The concept of a JIT should be approached from the crime’s international and cross-border dimension, rather than the seriousness of the crime.

When considering whether to establish a JIT, investigators, prosecutors and/or judges from the member states, together with delegates from Europol and Eurojust, should have a ’round table’ discussion about the relevant matters at the earliest opportunity, before any formal process or agreement is prepared.


Based in The Hague in the Netherlands, Eurojust is a legal body of the European Union set up to improve the effectiveness of investigating and prosecuting serious and organised cross-border crime. EU member states are represented by a prosecutor, investigator or judge. Eurojust may act through its members or as a college.

Legal framework

The Crime (International Co-operation) Act 2003 (CICA) provides the domestic legal framework for UK police providing assistance to a foreign jurisdiction investigation.

The Police Act 1996 section 26 provides that a local policing body may give assistance to international organisations and overseas police authorities. It allows for the body to temporarily second a member of the police force. This person is maintained by the policing body. However, such action requires the consent of the secretary of state.

The Swedish initiative aims to simplify and speed up the exchange of information and intelligence between law enforcement authorities of the EU member states. To achieve this it establishes rules to govern the practice of exchange, and places obligations on every member state to cooperate in the exchange of information and intelligence in criminal investigations and intelligence operations.

The Schengen agreement contains a number of intergovernmental arrangements to ensure the security of the public and the member states. In order to control and trace the movement of wanted people and missing property across national boundaries, a common IT system for exchanging information has been introduced. It is called the Schengen information system (SIS).


To meet the operational requirements set out in the Schengen agreement, every Schengen member state must establish a central authority as a single contact point for exchanging supplementary information related to SIS data.

This contact point is referred to as SIRENE (supplementary information request at the national entries). The UK SIRENE bureau is being established within the multilateral branch of NCA in the North-West hub.

Page last accessed 11 December 2018