Investigation - Stage 3: Prepare the investigation - Additional guidance

Key Decision log

What is a key decision log?

A key decision log (KDL) is a contemporaneous record of the key decisions that affect the course of an investigation and the reasons for those decisions.

A KDL is not a diary of the actions taken, nor is it meant to substitute for an investigation notebook, which should be maintained separately.

It is essential that only one KDL be maintained per investigation to ensure a coordinated investigation strategy and overall management control

What to record

The KDL is not intended to capture every decision made during an investigation.

Key decisions are the decisions taken in the management of an investigation that materially affect the course of the investigation.

Routine investigation decisions and decisions that merely reflect the implementation of the Investigation procedure, for example, should not be recorded.

Key decisions are likely to be made on the following issues (this list is not exhaustive):

  • liaison with emergency services or other enforcing authority on site
  • liaison with site management/control
  • primacy under work-related death protocol
  • involvement of specialist(s) and/or independent expert(s)
  • media strategy
  • instructions given to dutyholder.
  • health and safety implications eg immediate danger, prevention of further harm
  • preservation of evidence
  • resource allocation/withdrawal
  • witness evidence, witness identification, vulnerable witnesses, interview strategy
  • interpreters and translators
  • suspect identification, unsolicited comments, interview strategy
  • documentary and real evidence
  • prioritisation of actions
  • contact with bereaved family
  • issue of notices

It is equally important to record decisions and reasons for not doing something as for doing something and to record any changes or retractions of previous decisions.

The information received on initial notification of the incident should be recorded because this informs the initial investigation and visit strategy and helps to explain the decisions made very early on in the investigation.

How to record

  • entries should be made as soon as possible after making the decision
  • any significant delay between making the decision and recording it should be explained
  • all recorded decisions must be dated and timed
  • entries must be signed by the inspector in charge of the investigation and also by the person making the decision, if they are not the inspector in charge
  • only one decision should be recorded on each page
  • recording should be proportional to the incident under investigation
  • the entry should not inadvertently suggest that opinion on culpability has been reached before reasonable lines of inquiry have been followed and relevant evidence has been considered
  • wording is important: time should be taken to consider the entry so that it is an accurate, understandable record of the decision and reasons
  • the record in the KDL should enable someone who is not directly involved in the conduct of the investigation to understand the thought processes of the investigator and the reasons for the course of the investigation - this is important for defending any challenges made against decisions and for any reviews of the investigation.

Use of Contacts and Index sections

These sections are optional.

The index will assist people not familiar with the log to locate decisions within the book when necessary, eg at review or when the course of the investigation changes or decision made earlier are changed.


The KDL is an A4 bound book with a unique serial number and individually numbered pages.

Supplies are held by HSE offices.

Printed in the KDL are guidelines on its use, together with an indication of the types of decisions that should be recorded.

Maintenance, control and retention

Inspectors likely to be responsible for an investigation should hold a blank KDL for immediate use.

The inspector in charge of the investigation (the investigation manager of a major incident or the investigating inspector) will usually make the key decisions and should keep the KDL in their possession.

Where decisions are made by others, for example the line manager during reviews, or another inspector involved in the investigation, the inspector in charge of the investigation should still enter and sign the key decision in the log. The person making the decision should also sign the entry.

For large investigations it is important to hold review meetings, for example end of day team meetings, to ensure that all key decisions with attendant reasons are accurately recorded. The log belongs to the investigation and is available to the investigation team but care should be taken regarding access where sensitive issues are dealt with.

At the completion of the investigation, the KDL must be scanned into COIN.

The paper copy should be retained with the other investigation papers for the minimum period required by the CPIA (England and Wales) and in accordance with HSE's retention schedule of 5 years for a minor file or 9 years for a major file before first review.


HSE investigations, and those of other investigating authorities, are coming under increasing scrutiny from external organisations, including pressure groups. Decisions made during investigations are consequently being challenged more frequently.

The introduction of KDLs across operations group is important. KDLs will help HSE to demonstrate that key decisions made during the course of an investigation have been taken in accordance with relevant powers and duties and that all relevant matters have been considered at the time the decision was taken.

Recording of key decisions is required under the Work Related Death Protocol (the police have a well established system of using policy logs) and by OC 130/8 Prosecuting individuals. Prior to KDLs, there has been no means of recording this information in a consistent manner.

KDLs will help investigators to demonstrate that all reasonable lines of enquiry have been followed, and will provide justification for not following or for discontinuing lines of enquiry.

Whilst an investigation is ongoing, the KDL will assist in the management of the investigation by helping to structure the thoughts of the investigator and line manager, and will help in the monitoring and review of the investigation as required by the Investigation procedure.

The KDL should enhance communication with all those involved in the investigation, especially following staff changes, helping them to be clear about the direction and priorities of the investigation. They will assist the line manager and others to understand the thought processes of the investigator and to offer advice and support as appropriate.

After an investigation has been completed, the KDL can assist management review of the quality of an investigation by facilitating internal consideration and discussion of investigation decisions.

Recording the rationale behind decisions at the time they were made can explain why they were correct in the circumstances and on the basis of the information existing at the time, and without the benefit of hindsight. This will be helpful in explaining to third parties that a logical decision making process was followed, and why decisions were changed or the course of the investigation was changed in the light of developing information and events.

Decisions may be challenged several years after they were taken, for example during legal proceedings. Such challenges can be difficult to defend without contemporaneous records of the reasons behind the decisions.

KDLs also provide accountability and transparency in justifying decisions, including those about resourcing of relative priorities, and of task allocation between investigators.

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Updated 2022-08-16