This page is from APP, the official source of professional practice for policing.
Every police investigation has its own unique circumstances. These circumstances influence the response provided. Chief officers should balance other organisational priorities with the ability to provide ongoing support for investigators to investigate effectively. Chief officers should also ensure that the force meets its duty of care to the public, officers and staff, as well as ensuring that processes are in place to support a learning, reflective culture where officers can develop their skills.
Irrespective of the size or complexity of an investigation, the investigator will need to manage a number of factors when conducting an investigation. This will include:
- working with people
- threat, risk and harm
- investigative strategies
Managing these factors in volume crimes may be more straightforward than in complex investigations.
Priority and volume crimes are often investigated by one investigator, supported by their supervisor, and helped to varying degrees by crime scene investigators (CSIs) or other specialists. The investigator will often be responsible for managing a caseload of several individual investigations.
In major or serious and organised crime investigations, a senior investigating officer (SIO) will be allocated to lead the investigation. This means they have two roles – lead investigator and manager.
The SIO should be able to:
- develop investigative strategies based on the unique circumstances of each case
- make effective use of the national decision model
- continually assess and modify their strategies as new material becomes available
- ensure that information management systems are established, to enable the investigation to manage the volume and variety of information that will flow into and out of the investigation
- identify and request the resources necessary to undertake an effective investigation
- consider the resilience and wellbeing of the whole investigation team, including themselves
For further information, see:
Investigators must identify the resource needs of an investigation at the earliest opportunity. These will vary depending on the crime type and whether it is a priority and volume crime or a major investigation. See Practice advice on the management of priority and volume crime (National Policing Improvement Agency (NPIA), 2009).
The investigator must consider the appropriate level of investigative response, the availability and cost of the required resources, and whether their use is necessary and proportionate. Supervisors can inform and support decision making.
Resource types include:
- Police officers and staff.
- Witness liaison.
- forensic providers
- internal digital forensics
- National Crime Agency (NCA) experts
- National Police Chiefs’ Council (NPCC)
- partner agencies (for example, social services, referral centres)
- prosecution team
- scenes of crime services
- specialist support teams (for example, the Hydrant programme)
- victim and witness support groups
- Community leaders, representatives and members.
- General public.
- Community support groups and partnerships.
- Partner agencies.
- Third-sector groups.
- Central funding.
- Local funding.
- Budget holders:
- victim and witness management
- staff overtime
- Expenditure authorisations.
- National and local intelligence systems (for example, the Police National Database, the Police National Computer and the Tackling Organised Exploitation programme).
- Crime management systems.
- Covert human intelligence resources.
- Surveillance (conventional, technical, overt, covert).
- Office materials.
- Detention facilities.
- Interview facilities.
- Storage facilities.
- Technology (for example, CCTV, automatic number-plate recognition, mobile data).
- Exhibit store.
- Airwave terminals.
- Social media.
Prioritisation and proportionality
Investigators will need to prioritise the needs of the investigation against the available resources when they are limited.
Some resourcing decisions in priority and volume crime investigations will primarily be driven by local force policies and budgets. Where the investigator believes that specialist or technological resources will enhance an investigation, they should discuss this with their supervisor.
Tactical tasking and coordination meetings and/or local tasking meetings will often dictate the level of response and resources that is available to priority and volume crime investigations. This will reflect local policing priorities.
The use of expert advisers should be considered carefully, as part of the overall use of resources.
For advice on resource management during a major investigation, see:
Working with people
Working with people is integral to any investigation. There are five broad groups the investigator must consider.
- Colleagues within the police service (for example, peers, supervisors and specialists).
- Individuals who may help an investigation or provide material to the investigation (for example, victims, witnesses, suspects and expert advisers).
- Colleagues from partner agencies (for example, the local authority or social services).
- Solicitors or legal representatives (for example, the Crown Prosecution Service (CPS) or defence counsel).
- Local community or wider family who may be affected by a crime – an independent advisory group can provide community insight to support an investigation.
Investigators’ attitudes, behaviours and communication skills can have an impact on others, including colleagues, victims, witnesses and suspects. In some cases, how the investigator works with others can influence the outcome of a case.
When working with others, investigators must:
- act ethically and with integrity
- be able to recognise diverse needs and different perspectives
- take conflicting points of view into account
- identify the vulnerabilities and needs of victims, witnesses and suspects
- offer sensitive and effective support and safeguarding where needed
For further information, see our:
- Obtaining initial account guidelines
- Code of Ethics
- Effective supervision guidelines
- Conducting effective investigations guidelines
- Police Race Action Plan
See also the following professional profiles.
- Investigator Professionalising Investigations Programme (PIP) level 1
- Investigator PIP level 2
- Level 3 – Manager or expert advisor
- Level 4 – Service function leader
Impact of social media
An incident may be filmed by a bystander or witness and quickly posted onto social media. This means that in some cases, the family of a victim can find out about an incident before the police have been called or attend.
This presents significant challenges for investigators, who will need to be sensitive when talking to families and when countering potential misinformation posted on social media. An open, honest and transparent approach will build confidence and create trust.
- APP on Engagement and communication
- APP on Media relations
- Code of Practice for Victims of Crime in England and Wales (GOV.UK, 2020)
Officer and staff welfare
Investigators and senior officers should ensure that staff welfare needs are identified as soon as possible, and that support is available to reduce the potential harm suffered by an individual. Police officers and staff who deal with disturbing or traumatic incidents may suffer adverse effects in relation to an individual incident and/or as a result of an accumulation of exposure over a period of time. On an emotional or behavioural level, people react differently to traumatic situations or incidents. Investigators and senior officers should ensure that they take individual needs into account.
Support should include pre-deployment risk assessment and regular screening, as well as self-referral. These resources should apply to all investigations, and to all police officers and staff (with particular emphasis on high-risk roles).
Serious and long-standing enquiries
The welfare of staff involved in traumatic, complex or long-standing enquiries should be a priority for SIOs when establishing the investigation team. Force systems and procedures should include compulsory welfare screening, team briefings and debriefings, or pre-deployment screening before a particularly traumatic investigation (for example, a child death).
Consideration should be given to the following.
- The duty of care to staff involved in the investigation.
- Force occupational health provision (for example, psychological screening and support programmes).
- Proactive supervisory engagement with staff, to identify welfare and support needs.
- Effective exit interviews to understand why staff may request to leave an investigation.
Investigators working within specialist units, such as child abuse investigation and rape and serious sexual assault, are not only managing high volumes of caseload but are continuously exposed to traumatic events.
Reducing the impact of primary and secondary trauma in specialist roles is explored in a our guide, Responding to trauma in policing. This includes exit plans from specialist roles, as well as models that have a strong evidence base of success with emergency service personnel.
Welfare of others involved in the investigation
The investigator should be mindful of the potential impact that trauma may have on others involved in the investigation, including victims, witnesses and suspects.
- the Family liaison section of the APP on Investigation – Working with victims and witnesses
- APP on Mental health
The role of the police role is to signpost individuals to support. Investigators should remind those involved throughout the investigation that access to support may be taken up at any stage throughout the investigation. They should also be mindful that asking victims and witnesses to revisit traumatic events may cause additional stress.
For further information on welfare, see:
- APP on Critical incident management
- the National Police Wellbeing Service (Oscar Kilo)
- Wellbeing of investigators toolkit
- Major crime investigation manual (NPCC, 2021)
- Effective supervision guidelines – Supporting wellbeing
- APP on Staffing and the child abuse investigation unit – Staff welfare and support in child abuse investigations
- APP on Managing critical incidents – The impact of an incident
- information about our wellbeing services
Expert advisors (EAs) are independent subject matter specialists, who can assist an investigation by using their specialist knowledge and expertise. An expert is defined by the CPS as:
a person whose evidence is intended to be put before a court and who has relevant skills and/or knowledge achieved through research, experience or professional application within a specific field sufficient to entitle them to give evidence of their opinion and upon which the court may require independent and impartial assistance. The difference between an expert and other witnesses is that experts are the only witnesses allowed to give opinion evidence.
Investigators should make themselves aware of any local force policy before engaging an expert.
It is the investigator’s responsibility to:
- ensure that the EA has the necessary security clearance according to local force policy – this is particularly important where the EA will need access to sensitive material
- agree terms of reference and a contract with the EA before they start work
- provide the necessary material or information needed by the EA to perform their role
- respect the objectivity and independence of the EA and not pressurise them to give a particular answer
- ensure that the EA gives opinion on facts and hypotheses for which they have been properly prepared and briefed
- ensure that the EA understands their:
- responsibility to assist the investigation and comply with the Criminal Procedure and Investigations Act 1996 (CPIA) and the revised codes of practice issued under it
- responsibilities as defined in the NPIA's Practice advice for expert advisers (2011)
- disclosure obligations and confidentiality – see APP on Charging and case presentation – Disclosure
- develop and maintain clear lines of communication with the EA and provide guidance or updates throughout the investigation that may have an impact on their work
Investigators should confidently challenge an EA’s opinion if they seem to be disregarding relevant facts or material.
Managing threat, risk and harm
Investigators must be able to:
- recognise risks and their potential impact on individuals, the investigation or the organisation
- make appropriate decisions to manage or mitigate risk
- keep detailed records of decisions and the rationale for those decisions
- communicate details of the risk and/or the strategies put in place to others (for example, colleagues, victims, witnesses or suspects)
Investigators and SIOs constantly make decisions about investigative actions, based on incomplete information and in uncertain conditions. All areas of policing are susceptible to threat, risk and harm. There is an obligation on the police to identify, assess and manage risk to prevent or reduce the likelihood and impact of threat and harm. Legislation – for example, on health and safety or human rights – places specific demands on investigators to prevent and reduce the likelihood or impact of harm to people, their property or reputation.
Using risk assessment tools, such as impact versus likelihood, can help the police to assess risk and can identify relevant strategies to manage or mitigate that risk.
Investigators must recognise that particular aspects of an investigation may be susceptible to threat, risk and harm, including the following.
- Investigative parameters – failing to keep the big picture in mind, being too narrowly focused, failing to consider all available hypotheses, failing to assign sufficient time or resources.
- Material and evidence collection, analysis or presentation – accepting information at face value, allowing material or evidence to be contaminated or corrupted, failing to quality assure and to challenge statements, failing to verify information.
- Individuals or groups – not providing them with timely advice or information.
- Victims and witnesses not supporting an investigation or failing to attend court as required – not listening to victims’ concerns, focusing on the victim and not investigating the suspect, not facilitating familiarisation visits to court.
The measures to manage these risks can range from the relatively simple, such as crime prevention advice, to the complex, such as providing witness protection.
For further information, see:
Investigators must keep an auditable record of their decisions, the reasons for taking a particular investigative action, and the outcome where relevant. Records should be made in a timely and proportionate way. Recording this information enables accountability and transparency, and provides a record of the investigation for reviews and handovers.
Comprehensive record keeping provides an overview of the investigation and can be used to record:
- investigative actions
- investigative strategies used
- risk assessments
- resource considerations
- briefing and debriefing
- health and safety considerations (see Managing threat, risk and harm)
Records may be kept in different formats depending on the seriousness and complexity of the crime under investigation, and on local force recording systems. Common formats include:
- crime reports for most types of volume crime investigations
- policy files or key decision logs for serious or complex investigations
The use of policy files is set out in section 1.6 of the Major crime investigation manual (NPCC, 2021).
Investigators should consider the following strategies when appropriate and proportionate to the case.
- Internal and external communications strategy.
- Financial investigation.
- Forensic strategy.
- House-to-house enquiries.
- Intelligence strategy.
- Digital strategy, including passive data generators.
- Pathology strategy.
- Reconstructions (see section 2.14 of the Major Crime Investigation Manual (NPCC, 2021)).
- Scene strategy.
- Search strategy.
- Suspect strategy (see the trace, investigate and evaluate (TIE) strategy, and the identification of suspects and arrest strategy).
- Victim and witness strategy, including family liaison.
- Covert policing strategy.
The disclosure process is a critical part of the investigative and prosecution processes enshrined in the right to a fair trial. It is about fairness, the professional handling of materials and evidencing diligence within a good investigation.
Revelation of materials to CPS and disclosure is an integral part of the investigation that supports prosecutions. In complex investigations, the management of disclosure can be challenging. The development of an investigation management document (IMD), updated regularly throughout an investigation, will support discussions with CPS about what should and should not be disclosed. CPS use the content of the IMD to complete a disclosure management document (DMD) that will enable the court to assess the fairness of the disclosure processes applied during the investigation. This helps refine any issues with cases earlier and faster.
Disclosure is supported when an investigator conducts all reasonable enquiries and gathers relevant material. Investigators should remember the following points.
- Record – keep a log of material and enquiries made.
- Retain – keep material in a durable format and/or copy.
- Review – material should be reviewed to determine whether it:
- is relevant to the prosecution case (used material)
- is not relevant but might reasonably be considered capable of undermining the case against the accused, or of assisting the case for the accused (unused material)
- has not previously been disclosed
- would undermine the public interest and would risk exposure of sensitive tactics or material (sensitive material)
- Reveal – if a prosecution takes place, the material will be revealed to the prosecutor on schedules (used, unused and sensitive).
Not everything that is revealed to the CPS is disclosed to the defence. Generally, a prosecutor’s duty to disclose unused material to the defence will be triggered by a not guilty plea or a committal.
See APP on Charging and case preparation for further information on case files and working with criminal justice partners.
Responsibilities of a disclosure officer
The disclosure officer is responsible for assessing, summarising and scheduling all material gathered on the enquiry. They ensure that comprehensive disclosure schedules are applied to the examination and revelation of all relevant unused materials, including the application of descriptions and relating to decisions of sensitivity of materials. They ensure that all materials are disclosed in line with applicable legislation and guidance. The disclosure officer works with the SIO and CPS in relation to any issues that might undermine the prosecution’s case.
See the disclosure officer role profile for key accountabilities.
The investigator will gather material in a variety of formats, including physical, digital, documentary or biological. This material is referred to as exhibits and requires collation, examination and storage to maintain its integrity and provenance. The investigator must keep accurate and comprehensive records of all exhibits throughout an investigation. As each exhibit is recovered, a record should detail the:
- precise description of the material recovered
- precise location of recovery
- time, day and date of recovery
- individual who recovered it
- location and method of storage
The continuity of exhibits must be maintained, and every movement and transfer must be accurately recorded. If the material is removed from storage for any reason, or transferred – for example, for forensic examination – this should be recorded.
The record should detail the reasons for the movement, the name of the person who removed it, when it was removed and to whom it has been transferred.
Advice on recovery, handling and storage of exhibits can be obtained from CSIs, crime scene managers or supervisors.
Digital exhibits management
Digital material could come into the investigation from a variety of sources and should be treated as a key investigative strategy. The nature of the material will depend on how and why the crime was committed. In some cases, the offence may be committed using a digital device (such as phishing), or digital material can be used to prove or disprove, for example, a suspect’s relationship to the victim or their presence at a crime scene (such as the suspect leaving a digital footprint by connecting their device to the victim’s router).
When identifying digital material, investigators will need to consider how best to recover and store it and may need advice from digital forensics experts.
Care should be taken to avoid digital material being lost, damaged, destroyed or concealed. For example, other digital devices at a crime scene, including those carried by emergency responders, may corrupt available digital material.
Digital material as an exhibit should be managed in the same way as physical evidence when considering continuity and integrity. As with physical evidence, there is also the need to avoid the digital material being altered or destroyed during examination or storage. See local force policy for advice on correct storage, retention and examination of digital material.
In large-scale enquiries, a dedicated exhibits officer may be appointed by the SIO. They should maintain a close working relationship with the investigating officer to ensure that they are aware of all developments in the investigation and can bring significant items to the attention of the investigator at the earliest opportunity.
Responsibilities of an exhibits officer
These include liaising with CSIs and forensic service providers to ensure that the recovery, handling, storage and submission of all relevant exhibits is undertaken, and that the integrity of exhibits is preserved to avoid contamination. See the exhibits officer role profile for further information.
For further information relevant to managing investigations, see our guidelines on: