The ICO exists to empower you through information.

The Commissioner has produced general guidance on carrying out the public interest test. This section looks at those factors which are particular to section 31.

Many of the public interest arguments that apply to section 30 apply to this exemption too. For example, if you are not a police force yourself, but are withholding information to avoid harming a police investigation, you could rely on very similar arguments to those that the police force might use, if they were asked for the same information.


In Reginald Charles Hargrave v Information Commissioner and The National Archive (EA/2007/0041 3 December 2007) the appellant had requested information from a police investigation into an unsolved murder that took place in 1954. The National Archives now held the information. They refused to disclose it, relying on sections 31(1)(a),(b),(c). Although the case was very old, the National Archives produced evidence that persuaded the Tribunal that there was a significant possibility that police could identify and prosecute the killer in the future. The Tribunal found that the public interest favoured maintaining the exemptions claimed because disclosure would be harmful to any future prosecution.

There is a very strong public interest in protecting the ability of public authorities to enforce the law. The more serious the harm that could result from disclosure and the more likely it is that the harm will happen, the stronger the public interest will be in preventing that from happening.

However, section 31 covers a wide range of activities. It is important that you focus on the consequences of disclosing the actual information in question and the likelihood of those consequences occurring. You should not treat the exemption as absolute.

Protection from crime and its consequences

There is a clear public interest in protecting society from the impact of crime. The greater the potential for a disclosure to result in a breach of the law, or in helping those who breach the law to evade justice, the greater the public interest in maintaining the exemption.

Both organisations and people can be victims of crime. Although there is a public interest in protecting both, there is a greater public interest in protecting people from the impact of crime – particularly if they are vulnerable.

The impact of crime is not confined to its immediate victims, as the example below demonstrates:


In London Borough of Camden v The Information Commissioner & Yiannis Voyias [2012] UKUT 190 (ACC), the Upper Tribunal considered the appeal of a decision by the First Tier Tribunal (FTT). The decision ordered the council to disclose a list of unoccupied dwellings that were not owned by people. The council had relied section 31(1)(a), as they claimed that disclosure would prejudice the prevention of crime.

The FTT had agreed that those described as “organised squatters” would use the list. These are people who occupy properties simply in order to meet their housing needs. At the time of the request, squatting was not a criminal offence. The FTT considered that the only criminal activity that the organised squatters could commit would be any criminal damage caused when breaking into the properties. The council found the public interest arguments in favour of disclosure outweighed the public interest in preventing such crimes.

The Upper Tribunal disagreed. They argued that the council was entitled to “take account of any consequences that can readily be anticipated as realistic possibilities.” They found that the FTT had taken too narrow a view of the criminal activity caused by illegal occupation. For example, the FTT did not consider the risk of the theft of electricity. It was also appropriate to take account of the cost of removing those illegally occupying properties.

As well as the financial costs of crime, the Upper Tribunal noted that there were social costs too. In this case, any criminal damage was likely to reduce the quality of life in the area. Neighbours would live in fear of further crime being committed.

The Upper Tribunal also considered that disclosing the list could change the behaviour of other criminals. The FTT had previously found that, although criminals steal heating and water systems from empty properties, it was mainly building sites that were targeted. Therefore, the FTT did not take these crimes into account when assessing the public interest. The Upper Tribunal believed that this failed to take account of the likelihood that criminals would change their behaviour and take advantage of the list to target those properties too.

The two most important points you should bear in mind from the above case are:

  • the need to take account of any consequence that is a realistic possibility; and
  • the relevance of the social or psychological effects of crime.

You can only take account of consequences that are realistic possibilities. Public authorities cannot take account of crimes, or any consequences of those crimes, which are too speculative or fanciful.


In London Borough of Camden v The Information Commissioner & Yiannis Voyias [2012] UKUT 190 (ACC), the Upper Tribunal explained what public interest factors the First Tier Tribunal should have taken into account when assessing the balance of the public interest. These included preventing not just the act of criminal damage when squatters enter a building, but the consequences that would follow. This includes the direct costs of repairing property and the cost of evictions. The Tribunal also needed to take account of indirect costs, such as the impact on local property values and higher insurance premiums that might arise from an increase in crime.

However, public authorities should exclude more fanciful potential consequences. For example, in this case, it would not be appropriate to consider “…the possibility of a flying splinter blinding a passing child.” (paragraph 11)

The consequences of crime also include the increased fear of crime. These psychological factors may not always be proportionate to the actual risk. People in the surrounding area may feel more vulnerable to crime than they actually are. Nevertheless, you can take into account the likely impact on people’s fear of crime when considering the public interest in maintaining the exemption.

Section 31 is not solely concerned with criminal activities. There can be as great or, in some circumstances, a greater public interest in protecting the other law enforcement activities covered by section 31. For example, preventing someone from being involved in a fatal accident at work. You should consider each case on its own merits, taking account of the actual harm that could be caused by disclosure, together with all the circumstances of the case.

The public interest in maintaining an exemption is limited to the interests that are inherent in that exemption. You can only consider the consequences of the harm that the exemption guards against.


Someone makes a request for the specifications of your security system. You rely on section 31(1)(a) to withhold the information, on the basis that it would reveal how to undermine your system and make your property vulnerable to break-ins.

When considering the public interest in maintaining the exemption, you could take account of the consequence of those break-ins. This could include disrupting the work of your staff if the equipment they need has been stolen and the cost of installing new security systems.

You could not take account of any harm that might arise to the commercial interests of the company providing the security system. This is because those consequences do not concern the crimes that would result from disclosing the information. However, if you could demonstrate that disclosure could harm your supplier’s commercial interests, you may be able to rely on section 43 of FOIA as well.

Harm to investigations

Many of the activities protected by section 31 will involve some form of investigation. When applying this exemption, you should think about the purpose behind the investigation, ie the interest protected by the exemption. For example, the public interest in identifying medical professionals who are unfit to practice, or in discovering the cause of an accident so that people can stop it from happening again. There will be a very strong public interest in ensuring that such investigations can reach thorough and fair conclusions.

The public interest in protecting the integrity of an investigation is likely to be strongest whilst the investigation is ongoing. This is because that is when disclosure is likely to have the most harmful effects (such as giving a suspect the opportunity to destroy or conceal evidence). The public interest in maintaining the exemption is likely to fall once an investigation has concluded, the results are made public and any proceedings which arise out of the investigation are completed.

However, even after an investigation has concluded, there may still be a public interest in preventing the disclosure of information. This applies if that disclosure could make such investigations more difficult to conduct in future (for example by dissuading witnesses from coming forward).

There may often be a strong public interest in disclosing the outcome of an investigation, but a strong public interest in withholding the investigative steps or considerations leading to it.

Investigators need private thinking space if they are going to explore all aspects of a case fully, without fear that the press will report on their half-formed opinions or that those opinions will enter the public domain. Such concerns could hinder the efficient running of an investigation. Investigators may expect to make their findings public eventually, but usually at a later stage, when the findings represent the fully considered conclusions of the investigation.

There will be a strong public interest in maintaining the exemption if disclosure would make it harder for an organisation to acquire the information they need, thereby hampering their ability to discharge their functions.

Public interest in favour of disclosure

You should bear in mind that there is also a public interest in disclosing information that holds law enforcement bodies to account and increases transparency about how they perform their functions. Without such information, the public may lack confidence and trust in these bodies.

The public interest test requires that you consider all the circumstances of the case. This includes the significance of the information itself and the issues that it addresses.


Decision notice FS50173181 concerned a request for a manual detailing the physical restraint methods used on young people in secure training centres. The request was made to the Youth Justice Board for England and Wales and was withheld under section 31(1)(f) – security and good order in prisons.

The exemption had been engaged on the basis that providing details of methods of restraint and the circumstances in which staff could use them, would enable young offenders to counteract the techniques. Since staff used the techniques regularly, the disclosure could have a serious impact on the ability of the authorities to maintain good order in secure training centres. There was, therefore, a strong public interest argument in favour of maintaining the exemption.

However, at the time of the request, there was also a serious public debate on using such techniques. This followed the death of two young offenders on whom staff used those techniques.

There was also official recognition that, at the time of the request, there was no proper framework for assessing the safety of such methods.

The Commissioner found that there was a significant public interest in informing the debate on the use of physical control methods on children. He ordered the disclosure of the information.

Five years later, in decision notice FS50478716, the Commissioner found that the MoJ was entitled to withhold a similar document. This document concerned restraint techniques used on slightly older detainees. In his analysis, the Commissioner was satisfied that there was now a considerable amount of information about the use of safeguards in the public domain, as well as stricter procedures for recording incidents. The Upper Tribunal upheld this decision.

Probity of investigations

It is important that the public have confidence in the public authorities responsible for enforcing the law. There is a general public interest in disclosing information that promotes accountability and transparency in order to maintain that confidence and trust.

It is not uncommon for people to make allegations that an investigation lacked thoroughness or was biased. However, a mere allegation will not carry much weight. You should decide whether there is a genuine basis for suspicion, even if it is not actually proven. You could find a genuine basis in the facts and the content of the requested information. If you hold information that would reveal wrongdoing in the conduct of an investigation, this would be a strong public interest factor in favour of disclosure.

You should also take into account the outcome of any independent investigation or review of probity and any evidence of public concern. If an “investigation into the investigation” has shown that errors were made, there is likely to be a stronger public interest in disclosure.