'To allow the prompt and effective investigation of the offence' is a familiar reason given by police officers to justify the arrest of a suspect. However, it is a requirement of a lawful arrest that a constable has reasonable grounds for believing that an arrest is necessary for that purpose. But what does the test of necessity mean and how should it be applied in practice? These were the issues to be decided by Slade J. in the High Court in Richardson v The Chief Constable of West Midlands Police [2011] EWHC 773. The case concerned a teacher, accused of assaulting a pupil, who sought damages for false imprisonment following his arrest at a police station at which he had attended voluntarily for interview. The decision is essential for defence practitioners who wish to make representations against the arrest of clients who voluntarily attend for interview.

The significance of an arrest, even where no further action is taken, should not be underestimated. For all clients, an arrest will involve at least a temporary restriction of liberty and samples of their DNA and fingerprints being taken and retained. For some, it may also result in damaging publicity. For others, the impact of an arrest alone can be harmful to career prospects and travel plans. For example, an arrest can result in difficulties in obtaining visas, particularly for entry into the USA. In some cases, the fact of an arrest can impair the career prospects of a suspect significantly.

Professionals who regularly care for children or vulnerable individuals, such as the Claimant in Richardson, are required to submit to an Enhanced Criminal Records Bureau ('ECRB') check on successfully gaining employment and at regular intervals thereafter. An ECRB check will provide employers with details of unspent and spent convictions, cautions and reprimands, along with details of any entries on the Independent Safeguarding Authority barred lists. In addition, pursuant to section 113B(4) of the Police Act 1997, a Chief Constable can disclose any information which he considers might be relevant to the applicant's employment and ought to be included in the certificate. Such information can include allegations, complaints and investigations, even where no charges or prosecution are brought. In the consideration of relevance, Chief Constables have to assess whether the information might be true. In marginal situations, for example, where it is unclear as to whether an allegation can be substantiated, an applicant should be given an opportunity to make representations to the Chief Constable. (See R (on the application of L) v Commissioner of Police of the Metropolis [2010] 1 AC 410.) Arguably, the lack of an arrest would be a factor tending against disclosure of such information.

In circumstances where a disclosure is made, the weight to which employers attach to an arrest (as opposed to an allegation alone) is underlined by an example from the case of Richardson. The Claimant's head teacher asserted that the Governors of the school, before coming to a decision on the internal disciplinary process, would want to know whether he had been arrested or not.

In that case, an allegation of assault on a pupil was made against the Claimant. He and his solicitor attended at a police station by appointment. The Claimant indicated to the investigating officer that he was prepared to be interviewed under caution. He was informed that he would be arrested in order for the interview to take place. The Claimant's solicitor objected to the arrest on the grounds that it was unnecessary. As the custody suite at the first police station was closed, the Claimant was asked to attend at a second police station. On arrival at that second station, the Claimant was arrested by the same investigating officer to allow for the prompt and effective investigation of the offence. Again, the Claimant's solicitor protested. The custody officer recorded that the arrest and detention were necessary as the allegations were serious, the arrest would cause little or no interference with the Claimant's liberty, and if the Claimant tried to leave mid-interview then he would have to be arrested and transported to a custody suite which would disrupt the flow of the interview. In total, the Claimant was detained for about two hours. Following the Claimant's interview, he was bailed and subsequently no further action was taken by the police.

For an arrest to be lawful the arresting officer must have (i) reasonable grounds for suspecting the person to be guilty of the offence; (ii) a ground of arrest listed in section 24(5) of the Police and Criminal Evidence Act 1984; and (iii) the officer must have reasonable grounds for believing that it is necessary to arrest the person in question pursuant to section 24(4) of the PACE.

As to the meaning of the word "necessity" in section 24(4), Slade J. considered the word "necessity" to be an ordinary English word which did not require further explanation. Her Ladyship acknowledged that the meaning of "the practical and sensible option" (as per Lord Chief Justice Kerr in Alexander and others: Applications for Judicial Review [2009] NIQB 20) may be useful in some circumstances but that this should not be adopted instead of the statutory language.

The High Court found that the arrest of the Claimant was unlawful because the necessity requirement was absent. He was awarded £1,000 for false imprisonment. The High Court found that there was no evidence as to whether, and if so on what grounds, the arresting officer had considered the arrest necessary. The custody officer's recorded reasons could not remedy the defects in the Claimant's arrest as there was no evidence that these were the reasons of the arresting officer at the time of the arrest. However, the Court went further and stated that even if the decision to arrest had been made by the custody officer with the reasons stated, the arrest would be unlawful. This is because the custody officer made no assessment of the likelihood that the Claimant would leave the interview and did not take into account the fact that the Claimant had voluntarily attended for interview at two police stations.

In practice, the necessity requirement of a lawful arrest will require a proper assessment of the individual circumstances of each case. It is clear that a cursory nod to the requirements of the PACE together with a generic reference to seriousness of the offence will not suffice. In the case of those voluntarily attending at police stations for interview, an arresting officer will be required to consider whether that attendance will achieve the objective of a prompt and effective investigation. As a result of the High Court's decision, it appears unlikely to be lawful to arrest a suspect on the basis of an unsupported risk that they might attempt to leave mid-interview. It follows that the use of the decision in Richardson coupled with full representations might prevent the unnecessary arrest of a suspect and the injurious impact that this might have.

As a final point, it is arguable that the decision may impact on individuals whom the police visit at home or work to affect an arrest for the purposes of searches and interviews. If those individuals cooperate fully and are willing to attend at the police station for immediate interview, then those would be factors tending against the necessity of an arrest for a prompt and effective investigation.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.