In previous legal updates we have described how, by the application of the principle of universal jurisdiction, certain offences, which can be broadly categorised as “war crimes”, can be prosecuted in the UK regardless of where they were committed and whether there is any nexus to the UK.

The offences falling into this category and which might be prosecuted in the UK are largely covered by three acts:  the Geneva Conventions Act 1957; Criminal Justice Act 1988 and the International Criminal Court Act 2001.

Previous updates on this topic:

The purpose of this update is look at the ways that cases may be selected for investigation and prosecution by state bodies in the UK. This is as distinct from those cases that are the subject of investigations by private individuals and NGOs who may on occasion apply for arrest warrants against individuals in the UK. The law regarding such applications will be the subject of a subsequent update.

Who investigates and prosecutes international crime?

The war crimes team of the Metropolitan Police Counter Terrorism Command (SO15) is responsible for the investigation of all allegations of war crimes, crimes against humanity, genocide and torture.

The Counter Terrorism Division (CTD) of the Crown Prosecution Service, Special Crime and Counter Terrorism Division (SCCTD) has responsibility for prosecuting any such crimes.

Guidelines for investigation and prosecution of international crime

SO15 and CTD have guidelines for the investigation and prosecution of allegations of war crimes, crimes against humanity, genocide and torture. 

The steps that need to be conducted for an investigation and prosecution of international crime include an initial scoping exercise by SO15, legal consideration and advice by CTD followed by a final investigative scoping exercise by SO15.

Initial Scoping of referrals to SO15 war crimes team

When a referral is received, the SO15 investigative team will conduct an initial scoping exercise to decide whether to initiate an investigation. Where appropriate, they will consult with partner agencies during this process.  The scoping will include the following:

  1. Establishing an identifiable suspect. Initial enquiries may be required in the UK or overseas to establish the identity of the suspect.  For offences of this nature this is often not straight forward and the information may not be held within the UK. Consideration will be given to whether the country where the information is held will provide mutual legal assistance (either formally or informally) to identify the suspect and, if not, whether there are other reasonable means of obtaining evidence of identification.  There will also be considerations about whether SO15 can conduct a safe and effective investigation in any overseas jurisdiction, including any risk of harm to the officers, victims or witnesses.
  2. Establishing the nationality and location of the named and identifiable suspect. There are different considerations for those that are crimes of universal jurisdiction (ie. grave breaches of the Geneva Conventions, torture or hostage taking) and those that are not.

Where there are crimes of universal jurisdiction, SO15 will be investigating whether the suspect is either present in the UK or if there is a reasonable prospect of them coming to the UK. If not, the matter will be referred to the Special Cases Unit of the Office of Security and Counter Terrorism at the Home Office for potential future immigration action, taking into account victim and witness safety issues.

Where there are crimes that do not have universal jurisdiction, SO15 will be seeing if the named/identifiable suspect is a UK national and if they are located in the UK or overseas.  If they are located overseas, is it a country from which the UK can extradite? If not the investigation will be suspended until there is a reasonable prospect of the suspect returning to the UK voluntarily.  If the individual is not a UK national then is he/she a UK resident as defined in S67A International Criminal Court Act 2001 (as amended by S70(4) Coroners and Justice Act 2009).

  1. Identification of victims/witnesses. Part of the scoping will include confirming if the victims/witnesses are named or identifiable and, if so, whether they are in the UK or abroad. If abroad, are they in a country which will provide mutual legal assistance or, if not, can the victims/witnesses be safely interviewed in a third country?  Where victims/witnesses are not named or identifiable, consideration must be made as to the prospect of identifying them and whether this requires enquiries in the UK or in the country where alleged crime(s) took place.  Again issues of mutual legal assistance, the ability to carry out a safe and effective investigation and if there are any other reasonable means of obtaining evidence of identification will be considered. At any stage, if the enquiries need to be made in a country which will not provide mutual legal assistance and an investigation is deemed to be impracticable then a referral can be made to the Special Cases Unit of the Office of Security and Counter Terrorism at the Home Office for potential future immigration action.  If an investigation is not possible SO15 will inform the identified victims/witnesses in accordance with the Victims' Charter.
  2. Consultation with International Criminal Court and ad hoc tribunals.   Part of the scoping exercise will include identifying if there any outstanding investigations in relation to the suspect or any witness.

Referral to CPS by SO15

Upon receipt of a referral from SO15 a CTD reviewing lawyer will consider and advise upon the potential offences, whether the UK has jurisdiction, whether the suspect could have immunity, what further enquiries may need to be conducted and where (including any issues of mutual legal assistance and/or safety issues related to the investigation) and the strength of the potential evidence.  The usual (non-urgent) time frame is to provide initial written advice to SO15 within 28 days. Where the Senior Investigating Officer (SIO) decides that an arrest should be made prior to receiving the written advice, the reviewing lawyer will provide advice as to jurisdiction and immunity and more detailed advice at a later date.

If the UK does not have jurisdiction or the suspect has immunity, SO15 will inform the victim or his/her solicitor.

If there are potential offences that could be tried in the UK, SO15 will decide whether or not to carry out a full investigation.

Final investigative scoping by SO15

SO15 will decide whether a safe and proportionate investigation is feasible taking into account factors above and the legal written advice.

If the decision is that a full investigation is feasible, a reviewing lawyer will advise on pre- and post-arrest matters. An early strategy meeting will be held and all key decisions recorded. If the case has been referred by a private individual, lawyer or organisation they will be informed. From that point all investigative decisions and the decision whether or not to arrest a suspect will be made by SO15 and any decision on prosecution will be made independently by the CPS in accordance with the Code for Crown Prosecutors. Consideration will also be made as to whether it is appropriate for the allegation to be referred to another government department for other potential action.

If it is decided an investigation is not possible SO15 will inform the victim(s) of the decision and the reasons for it as soon as reasonably practicable in accordance with the Victim's Charter. Any private individual, lawyer or individual who has submitted evidence on behalf of the victim(s) will also be informed in writing.


On completion of any investigation SO15 will submit a file of evidence to CTD. The CTD reviewing prosecutor will review it in accordance with the Code for Crown Prosecutors. If there is sufficient evidence it is highly likely that a prosecution would meet the public interest test. The Attorney General would then be asked to consent to the prosecution.