Section 24 PACE arrest and the necessity criteria explained

Quick answer

A constable can arrest without a warrant for any offence under s.24 PACE, but only if two tests are both met. First, the person is about to commit, is committing or has committed an offence, or you have reasonable grounds to suspect one of those (s.24(1) to (3)). Second, you must have reasonable grounds for believing that arrest is necessary for at least one of the reasons in s.24(5) (s.24(4)). Tell the person they are under arrest and why (s.28), and record why arrest was necessary (Code G paragraph 4.1).

If either test is not met, the power is not available, and an arrest is not lawful unless the person is told of it and the ground (s.28(1) and (3)). Code G paragraph 1.3 warns that an unjustified arrest may be challenged in court and could lead to civil claims for unlawful arrest and false imprisonment.

General information, not legal advice. Check the current law and your force policy.

The first test: suspicion of an offence

Section 24(1) covers four situations. A constable may arrest anyone:

• who is about to commit an offence
• who is in the act of committing one
• whom the constable has reasonable grounds to suspect is about to commit one
• whom the constable has reasonable grounds to suspect is committing one

Section 24(2) covers the case where you suspect an offence has been committed: you may arrest anyone you have reasonable grounds to suspect of being guilty of it. Section 24(3) covers an offence that has in fact been committed: you may arrest anyone who is guilty of it, or whom you have reasonable grounds to suspect of being guilty.

Code G paragraph 2.3A says there must be “some reasonable, objective grounds for the suspicion, based on known facts and information”. Note 2 adds that you should weigh facts that point away from the person too, including claims of innocence, before you decide.

The second test: necessity

Section 24(4) says the power is exercisable “only if the constable has reasonable grounds for believing that for any of the reasons mentioned in subsection (5) it is necessary to arrest the person in question”. Code G paragraph 2.5 says you, as the arresting officer, must be satisfied that at least one reason applies. Note 2C looks at all the circumstances at the time the decision is made, so record what you knew and what you considered.

Code G paragraph 2.8 tells you what to look at: the situation of the victim, the nature of the offence, the circumstances of the suspect and the needs of the investigation. Paragraph 1.3 asks you to consider whether less intrusive means could meet the aim. Note 2C says you do not have to be satisfied there is no viable alternative, but arrest should be the practical, sensible and proportionate option at the time you decide.

The s.24(5) reasons in plain words

Section 24(6) limits the public decency reason. It applies only where members of the public going about their normal business cannot reasonably be expected to avoid the person.

Name and address

Code G paragraph 2.9(a) says you might decide a name cannot be readily ascertained if the person fails or refuses to give it, particularly after a warning that this is likely to make arrest necessary. You may doubt a name they give if they seem reluctant or hesitant about it. If you have mobile fingerprinting, consider using it first to check a name (s.61(6A)). It may save you the arrest. Note 2D adds that a person warned they may be arrested should get a reasonable chance to establish their real name and address first, and should be told why what they have given or shown is not enough.

The same approach applies to the address (paragraph 2.9(b)). Where you are weighing a summons or postal charge, an address is satisfactory if the person will be there long enough for service, or someone there will accept it for them. For a penalty notice, it should be an address where the person will be found if enforcement action is needed.

Prompt and effective investigation

Reason (e) needs the most care. Code G paragraph 2.9(e) says it may arise where, without arrest, further action needed to investigate properly would be frustrated, unreasonably delayed or hindered. Its examples include:

• an interview where voluntary attendance is not a practicable alternative, for example because the person is unlikely to turn up, has made false statements or presented false evidence, or may steal or destroy evidence, collude with co-suspects, or contact or intimidate witnesses (2.9(e)(i))
• for an indictable offence, a need to enter and search premises without a warrant, to stop contact with others, or to detain for more than 24 hours before charge (2.9(e)(ii))
• for a recordable offence, a need to take fingerprints, footwear impressions or samples to secure or preserve evidence of that offence (2.9(e)(iii))
• for any offence, a need to search, examine or photograph the person to obtain evidence (2.9(e)(iv))

Note 2H rules out arrest just to take and check these routinely, with no prior grounds that they would give relevant evidence or help confirm identity.

If the reason is to interview, Note 2F says you must consider whether voluntary attendance is a practicable alternative. If it is, arrest is not necessary. If you did not consider it, you will not be able to show arrest was necessary to interview. If someone comes in by arrangement, Note 2G allows arrest on arrival only if new information has made voluntary attendance impracticable and it was not reasonably practicable to arrest them before they came in.

These are examples only. You still have to say, from the facts in front of you, why the action cannot be done without arrest.

Telling the person

Under s.28(1), a person not told at the moment of arrest that they are under arrest must be told as soon as practicable after. Under s.28(3), they must be told the ground at the time or as soon as practicable after. Otherwise the arrest is not lawful. Section 28(2) and (4) say this applies even where the arrest or the ground is obvious. The only exception, in s.28(5), is where it was not reasonably practicable because the person escaped before they could be told.

Code G paragraph 2.2 goes further. The person must be told the relevant circumstances of the arrest for both tests, and the custody officer must be given them on arrival. Paragraph 2.9 says that when practicable you should outline the facts and information that make arrest necessary. Note 3 says give them enough to understand they have lost their liberty and why, such as the nature of the suspected offence and when and where it happened, without vague or technical language. You need not give details that would undermine the investigation, for example before a formal interview.

The caution follows under paragraphs 3.4 and 3.5, unless it is impracticable because of the person’s condition or behaviour, or they were cautioned just before arrest.

What to record

Code G paragraph 4.1 requires the arresting officer to record in their pocket book or by another method used for recording information:

• the nature and circumstances of the offence leading to the arrest
• the reason or reasons why arrest was necessary
• the giving of the caution
• anything said by the person at the time of arrest

Make the record at the time unless that is impracticable, and otherwise as soon as possible after (paragraph 4.2). The information about circumstances and reasons is recorded in the custody record, or a copy of your own record is attached to it (paragraph 4.3). Paragraph 2.6 says you must examine and justify your reasons so the custody officer can decide whether to authorise detention.

Common mistakes

• Treating suspicion as the whole test. Having grounds to suspect only satisfies the first test.
• Writing a reason that is not on the list. “Serious offence” or “to teach them a lesson” is not in s.24(5).
• Writing “to investigate” and nothing else. Say which action needs arrest and why it cannot be done another way.
• Arresting to interview without considering a voluntary interview (Note 2F), or arresting someone who has come in by arrangement without new information (Note 2G).
• Ignoring what points away from the person. Note 2 expects you to weigh it.
• Not telling the person the ground because it seemed obvious. Section 28(4) removes that excuse.
• Giving the custody officer only the offence and not the reason arrest was necessary (paragraph 2.2).
• Skipping the alternatives. Paragraph 2.4 leaves you to decide whether to arrest, grant street bail after arrest, report for summons or postal charge, issue a penalty notice or take other action. Street bail is not an alternative to arrest. It comes after one, instead of taking the person to the station, and does not undo the need to arrest (Notes 2E and 2J).

Questions officers ask

Do I have to warn someone before arresting them for refusing their name?

A warning is not expressly required, but Code G Note 2D says officers should consider one if practicable. It can avoid the arrest, and if it is ignored it supports the need to arrest.

Is the seriousness of the offence a reason to arrest?

No. Seriousness is not one of the reasons in s.24(5), and that list is exhaustive (Code G paragraph 2.7). The nature of the offence is something you take into account when applying the reasons (paragraph 2.8).

Do I have to be sure there is no other option?

No. Code G Note 2C says you do not have to be satisfied there is no viable alternative, but arrest should be the practical, sensible and proportionate option at that time.

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Last checked 31 October 2026 against legislation.gov.uk and PACE Code G on GOV.UK. General information for officers, not legal advice: check the current law and your force policy.