Section 24 PACE
Power of Arrest
Comprehensive Authority Manual for Arrest Law, Necessity & Safeguards (2026)
Chapter 1
The Constitutional Purpose of Arrest Powers
The power of arrest represents the most significant intrusion into individual liberty that a state can exercise without a prior judicial warrant. In the United Kingdom, the constitutional purpose of arrest is not punitive; it is purely investigative. An arrest is a procedural tool used to bring a person into the criminal justice system to allow for the prompt and effective investigation of an offence.
Historical Context
Before PACE 1984, arrest powers were a fragmented patchwork of common law and disparate statutory provisions. This led to inconsistency in how citizens were detained and a lack of clear safeguards for the suspect.
Policing by Consent
The PACE Act codifies the principle of policing by consent by ensuring that every deprivation of liberty is governed by objective legal standards rather than the arbitrary discretion of an officer.
Section 24 of PACE was introduced to consolidate these powers into a single, comprehensive framework. It balances the state's need to investigate crime with the individual's right to liberty under Article 5 of the European Convention on Human Rights (ECHR). Liberty is the default state; arrest is the documented exception.
Chapter 2
Statutory Text of Section 24
Section 24 as it stands today was significantly amended by the Serious Organised Crime and Police Act 2005 (SOCPA). It removed the old distinction between "arrestable" and "non-arrestable" offences, making all offences potentially arrestable provided the necessity test is met.
Section 24(1) - Past Offences
"A constable may arrest without a warrant anyone who is about to commit an offence, anyone who is in the act of committing an offence, or anyone whom he has reasonable grounds for suspecting to be about to commit an offence or to be committing an offence."
Section 24(2) - Reasonable Suspicion
"If a constable has reasonable grounds for suspecting that an offence has been committed, he may arrest without a warrant anyone whom he has reasonable grounds to suspect of being guilty of it."
Section 24(3) - Committed Offences
"In the case of any offence which has been committed, a constable may arrest without a warrant anyone who is guilty of the offence, or anyone whom he has reasonable grounds for suspecting to be guilty of it."
Section 24(4) - The Necessity Test
"But the power of arrest 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."
This structure creates a two-stage hurdle for the officer: First, they must have reasonable suspicion (Stage 1). Second, they must have a reasonable belief in the necessity of the arrest (Stage 2).
Chapter 3
Reasonable Grounds for Suspicion
"Reasonable grounds for suspicion" is the fundamental objective test in UK policing law. It is a lower threshold than "reasonable belief" and significantly lower than "proof beyond reasonable doubt." However, it is more than mere a hunch or instinct.
The Objective Test
Grounds must be based on objective facts, information, or intelligence. A reasonable person, presented with the same facts as the officer, must be able to reach the same conclusion.
Information Sources
Suspicion can be formed based on eyewitness accounts, CCTV footage, forensic evidence, or police intelligence. It can even be based on information that would not be admissible as evidence in court.
Cumulative Grounds
Often, no single factor is enough to form reasonable suspicion, but the combination of several factors (e.g., location, time, behaviour) creates a cumulative basis for arrest.
Negative Thresholds: What Is NOT Reasonable?
Race, age, appearance, or religion can never be the sole basis for reasonable suspicion.
"Knowing" someone is a criminal or their previous convictions alone do not provide grounds for a new arrest.
Chapter 4
The Necessity Test (Code G)
Since 2005, having reasonable suspicion is not enough to justify an arrest. The officer must also show that the arrest is necessary. This is known as the "Necessity Test" and is governed by PACE Code G.
Statutory Grounds for Necessity (S.24(5))
An arrest is only necessary if it is for one of the following reasons:
Ascertaining Name/Address
If the person's name or address is unknown, not readily ascertainable, or the officer has reasonable grounds to doubt the name/address provided.
Preventing Harm/Injury
To prevent the person from causing physical injury to themselves or others, suffering physical injury, or causing loss or damage to property.
Public Decency/Obstruction
To prevent the person from committing an offence against public decency or causing an unlawful obstruction of the highway.
Child/Vulnerable Protection
To protect a child or other vulnerable person from the person in question.
Prompt and Effective Investigation
The most commonly used ground. Necessity is justified if an arrest is required to:
- Interview the suspect
- Search for evidence (S.18/S.32)
- Prevent evidence being destroyed
- Allow forensics/samples
Critical Note: If an officer cannot articulate why a voluntary interview (VA) would be insufficient to achieve these goals, the arrest may be deemed unlawful by a court.
Chapter 5
Arrest Procedure: What Must Happen
For an arrest to be lawful, it must be carried out in a specific, documented sequence. Failure to follow these procedural requirements under Section 28 of PACE can render the entire detention unlawful from the outset, regardless of the suspect's guilt.
1. The Fact of Arrest
The person must be informed that they are under arrest. Even if it is obvious (e.g., they are in handcuffs), the formal words must be spoken as soon as is practicable.
2. The Grounds for Arrest
The officer must state the specific offence(s) for which the person is being arrested. This must be clear—"arrested for theft" is better than "arrested for an offence."
3. The Necessity Grounds
Under Code G, the officer should also inform the person of the necessity for the arrest (e.g., "to allow for a prompt and effective investigation").
4. The Caution
"You do not have to say anything. But it may harm your defence if you do not mention when questioned something which you later rely on in court. Anything you do say may be given in evidence."
Once the arrest is formalised, the "PACE Clock" begins to run as soon as the person arrives at the police station (or in some cases, at the time of arrest if there is a delay). The suspect is now in the state's care, and their rights under Code C (Detention) and Code E/F (Interviewing) are activated.
Chapter 6
Arrest vs Voluntary Interview
In modern UK policing, a "Voluntary Interview" (also known as a Caution Plus 3 interview) is the primary alternative to arrest. If an investigation can be progressed without arresting the suspect, the necessity test for arrest is likely not met.
| Feature | Arrest (S.24) | Voluntary Interview |
|---|---|---|
| Detention | Compulsory; suspect is not free to leave. | Non-custodial; suspect can leave at any time. |
| Necessity | Must meet one of 6+ Code G grounds. | No necessity required; based on consent. |
| DNA/Fingerprints | Can be taken forcibly if required. | Usually taken voluntarily (S.61A). |
| PACE Clock | Starts on arrival at custody (usually 24h). | Does not exist; no time limit on interview. |
| Search Powers | S.18/S.32 activated after arrest. | Limited; usually requires consent or warrant. |
Strategically, the police prefer arrest when there is a risk of evidence being destroyed or a high risk of the suspect absconding. However, for most summary offences and many indictable offences where the suspect is cooperative, a voluntary interview is the legally safer and more proportionate route.
Chapter 7
When an Arrest Becomes Unlawful
An arrest is not "lawful" simply because a police officer says it is. It is a question of law that can be tested in the High Court or through a civil claim for false imprisonment. If any of the following conditions are met, the arrest is likely unlawful.
Lack of Objective Grounds
If the officer acted on a "gut feeling" without specific intelligence or observation, the Stage 1 test (Reasonable Suspicion) is failed.
Failure of Necessity
If the officer arrests a suspect who was willing to attend a voluntary interview, and no other ground exists (e.g., risk of harm), the Stage 2 test (Necessity) is failed.
Procedural Defects
Failing to inform the person they are under arrest or failing to state the grounds as soon as practicable as per Section 28 PACE.
Improper Motive
If the arrest is used as a form of "street justice," as punishment, or to simply "reset" the PACE clock from a previous detention.
Chapter 8
Consequences of Unlawful Arrest
1. Section 78 Evidence Exclusion
Under Section 78 of PACE, a court has the power to exclude evidence if its admission would have such an adverse effect on the fairness of the proceedings that the court ought not to admit it. If the very foundation of the evidence (the arrest) was unlawful, any subsequent confession or forensic sample may be excluded, often leading to a total case collapse.
2. Civil Litigation: False Imprisonment
Unlawful arrest is a "Strict Liability" tort. This means that if the legal requirements were not met, the police are liable for damages (compensation) regardless of whether they acted in good faith. Claims can cover:
- Loss of Liberty (per hour)
- Damage to Reputation
- Aggravated Damages (Malice)
- Exemplary Damages
3. Professional Misconduct
Officers who knowingly or recklessly carry out unlawful arrests may face internal disciplinary proceedings under the Police (Conduct) Regulations, as this constitutes a breach of the Standards of Professional Behaviour regarding 'Orders and Instructions' and 'Authority, Respect and Courtesy'.
Chapter 9
Arresting for Indictable vs Summary Offences
Before 2005, the power to arrest without a warrant was largely confined to "arrestable offences" (generally those with a five-year prison sentence). Today, Section 24 applies to all offences. However, the distinction between Indictable and Summary offences remains critical for other police powers, such as entry and search.
Summary Offences
Minor offences (e.g., common assault, low-level shoplifting) usually tried in the Magistrates' Court. While arrestable under S.24, the necessity test (Code G) is harder to justify if the suspect's details are known.
Indictable Offences
Serious offences (e.g., robbery, GBH) that can be tried in the Crown Court. For these offences, necessity for "prompt and effective investigation" is more easily justified due to the complexity and risk involved.
It is a common error to believe that police can only arrest for serious crimes. An officer can lawfully arrest for littering if the suspect refuses to provide their name and address (Necessity Ground A), making the arrest "necessary" to progress the prosecution.
Chapter 10
Arrest at Home: Section 17 PACE
Section 24 provides the *power* to arrest, but it does not provide the *power* to enter a private dwelling to execute that arrest. For that, an officer usually relies on Section 17 of PACE.
The Section 17 Threshold
To enter a dwelling without a warrant to arrest someone under Section 24, the officer must have reasonable grounds for believing that the person is on the premises, AND the offence must be an Indictable Offence.
If the offence is a Summary offence (e.g., simple criminal damage), police generally cannot force entry to a home to arrest under Section 24 unless they are in "Fresh Pursuit" or acting to save life and limb. Entering unlawfully to arrest renders the subsequent arrest a trespass and potentially unlawful.
Chapter 11
Use of Force During Arrest (Section 117)
Section 117 of PACE provides the statutory authority for a constable to use "reasonable force" in the exercise of any PACE power, including Section 24 arrest.
The National Decision Model (NDM)
Officers must justify force through the NDM, ensuring it is Proportionate, Legal, Accountable, and Necessary (PLAN).
Handcuffing Law
Handcuffing is a use of force. It is NOT mandatory for every arrest. An officer must justify why handcuffs were necessary to prevent escape or injury.
Excessive force during an arrest can lead to multiple legal consequences: an action in assault/battery, a successful internal misconduct investigation, or a "Use of Force" report being scrutinised for evidence of systemic bias. In 2026, Body-Worn Video (BWV) is the primary evidentiary tool for justifying these actions.
Chapter 12
Custody Authorisation After Arrest
The legality of an arrest is reviewed as soon as the suspect reaches the police station. Under Section 37 of PACE, an independent Custody Officer (usually of Sergeant rank) must determine whether there is sufficient evidence to charge or whether detention is necessary to secure/preserve evidence.
The "Gatekeeper" Role
The Custody Officer has the power to refuse detention if they believe the arrest was unlawful or the necessity test is no longer met. If detention is refused, the person must be released immediately.
Massive Authority FAQ
Common Questions Answered
Can police arrest without a warrant?
Yes. Section 24 of the Police and Criminal Evidence Act 1984 (PACE) allows a constable to arrest without a warrant if they have reasonable grounds to suspect an offence has been, is being, or is about to be committed, provided the arrest is 'necessary' under the criteria set out in PACE Code G.
What determines if an arrest is 'necessary'?
Necessity is determined by PACE Code G. Reasons include: to enable a name/address to be ascertained; to prevent injury or property damage; to protect a child or vulnerable person; or to allow the 'prompt and effective investigation' of the offence (e.g., to interview the suspect).
What are 'reasonable grounds' for suspicion?
Reasonable grounds must be based on objective facts, information, or intelligence. They are more than a hunch but less than proof. It means a reasonable person, given the same info, would come to the same conclusion.
Can you be arrested for a minor offence like littering?
Legally, yes. Since 2005, all offences are arrestable. However, for a minor offence, police must show why an arrest was necessary (e.g., you refused to give your name) rather than just issuing a summons or fine.
What is a voluntary interview (Caution Plus 3)?
A voluntary interview is a formal interview conducted under caution where the suspect is not under arrest and is free to leave. If a suspect agrees to a voluntary interview and there's no risk they'll flee or destroy evidence, an arrest may not be necessary.
Does an arrest always lead to a criminal record?
No. An arrest is a record of an investigation. It only becomes a 'criminal record' (conviction) if you are charged, go to court, and are found guilty or plead guilty.
Is resisting arrest an offence?
Yes. Under Section 89 of the Police Act 1996, it is a criminal offence to resist or wilfully obstruct a constable in the execution of their duty (which includes a lawful arrest).
Can police use force during an arrest?
Yes. Section 117 of PACE allows police to use 'reasonable force' if necessary to carry out an arrest. Force must be proportionate and justifiable under the National Decision Model.
Must police always use handcuffs during an arrest?
No. Handcuffing is a use of force and must be justified by the officer. They must believe there is a risk of escape, violence, or evidence destruction.
What happens if an arrest is found to be unlawful?
If an arrest is unlawful, evidence obtained as a result (like a confession) may be excluded under Section 78 PACE. The individual may also be able to sue the police for 'false imprisonment'.
Can a constable arrest someone on private property?
Yes, but they usually need a power of entry. Section 17 PACE allows police to enter private property to arrest someone for an 'indictable' offence if they believe the person is inside.
How long can police hold you after an arrest?
The standard limit is 24 hours. This can be extended to 36 hours for serious (indictable) offences by a senior officer, and up to 96 hours with a warrant from a Magistrate.
Do police have to tell you why you are being arrested?
Yes. Under Section 28 of PACE, you must be informed that you are under arrest and given the grounds (reasons) for that arrest as soon as is practicable.
What is 'Code G'?
Code G is the part of the PACE Codes of Practice that specifically deals with the power of arrest. It provides the detailed guidance that officers must follow to ensure an arrest is lawful and necessary.
Can a civilian make an arrest?
Yes, under Section 24A of PACE (often called a 'citizen's arrest'), but only for 'indictable' offences and where it is not practicable for a constable to make the arrest.
Can police arrest based on old information?
Yes, provided the suspicion remains reasonable and the arrest is necessary at the time it is made. There is no strict 'expiry date' for grounds of suspicion.
Is an arrest the same as being 'detained'?
An arrest is a specific type of detention for a suspected offence. You can be 'detained' for other reasons, such as a stop and search (Section 1 PACE) or for a mental health assessment (Section 136 MHA).
Can police arrest you for not answering questions?
No. You have a right to silence. However, not answering questions might make it harder to resolve the suspicion without an arrest, potentially satisfying the 'prompt and effective investigation' necessity ground.
Does an officer have to be in uniform to arrest?
No. Plain-clothes officers have the same power of arrest as uniformed officers under Section 24, but they should identify themselves as police and provide identification.
Can police arrest someone in 'fresh pursuit'?
Yes. If an offence has just been committed and the officer is chasing the suspect, they have broad powers to follow and arrest them, including entering properties in 'fresh pursuit'.