Can Police Detain Witnesses for Investigation?

When a crime is being investigated, members of the public may be asked to assist by providing information or attending a police station to give a statement. However, this raises an important legal question: can the police legally detain a witness as part of an investigation? This article explains the legal principles governing police powers in England and Wales, the difference between voluntary cooperation and detention, the circumstances in which someone may be held by police, and the rights and safeguards that apply. The content is grounded in current legislation, official guidance and legal standards.

What Does “Detention” Mean in Policing?

In policing law, detention generally refers to a situation where a person is not free to leave because of police authority. This can occur where someone is:

• Arrested on suspicion of committing an offence;
• Held in custody at a police station under statutory powers; or
• Subject to specific statutory stops (e.g. terrorism legislation) that permit limited holding.

It is important to distinguish between detention and voluntary attendance, where a person attends a police station or meeting to assist the investigation but is free to leave unless they are arrested. Under the Police and Criminal Evidence Act 1984 (PACE), there is no general police power to detain a witness simply because they may have information.

Police Powers and Witnesses

Voluntary Attendance and Interviews

Police often invite witnesses to attend interviews or provide statements voluntarily. A voluntary interview means a person chooses to attend to help with an investigation but is not detained and is free to leave at any time unless officers formally arrest them. This remains the default position in most criminal investigations.

While attending voluntarily, police may caution the person and take a statement, but they cannot prevent them from leaving unless there are lawful grounds to do so (e.g. arrest). A lack of cooperation by a witness does not itself justify detention.

Arrest Powers Under PACE

The police do have powers to arrest and detain suspects - but these powers are specifically tied to suspected criminal behaviour, not merely being a witness. Section 24 of PACE and its accompanying Codes of Practice set out the legal framework for arrest and detention. An arrest must meet a necessity test (for example, to prevent harm, secure evidence or ensure a suspect appears in court).

If a person initially attends a police station voluntarily and, during questioning, police decide that arrest is necessary, they must be informed they are under arrest and of the grounds for that arrest. Only at that point does detention under PACE apply.

Detention Without Arrest: Limited Scenarios

Specific Statutory Powers

There are narrow statutory exceptions where a person may be detained without being formally arrested, but these do not apply generally to witnesses in ordinary criminal investigations:

• Terrorism legislation (Schedule 7 of the Terrorism Act 2000) grants police powers to stop and detain individuals at ports and borders for questioning about involvement in terrorism activity. This can involve detention without arrest for a fixed period.
• Mental health and public safety powers, such as sections of the Mental Health Act, can allow temporary detention for assessment, but this is separate from criminal investigation detention.

These exceptional powers are specific, subject to time limits and have their own statutory safeguards. They should not be confused with powers relating to ordinary crime investigation.

Legal Safeguards for Detention

Requirement for Lawful Authority

Police cannot detain a person - witness or otherwise - without lawful authority. Detention without arrest must be explicitly permitted by statute. Simply having information relevant to an investigation is not enough.

Rights Upon Arrest

If someone is arrested during an investigation, statutory safeguards apply:

• They must be told they are under arrest and the grounds for it.
• Rights to legal advice and access to communication are triggered.
• Time limits on detention before charge apply (e.g., generally 24 hours, extendable in specific circumstances).

Time Limits and Custody

Custody Time Limits

Once a person is arrested, police may detain them in custody for questioning and investigation subject to statutory limits. Under PACE:

• The usual maximum period of detention without charge is 24 hours.
• A senior officer may extend this to 36 hours for indictable offences if necessary to secure or preserve evidence or question further.
• Courts can authorise further detention up to 96 hours total in serious cases.

These time limits are about suspects, not witnesses. A person who is genuinely a witness and is not arrested should not be held in custody.

Rights of a Witness

Voluntary Witnesses

A witness who attends voluntarily has the right to:

• Leave at any time unless formally arrested.
• Request legal advice if unsure about their role or the implications of giving a statement.
• Decline to answer questions, particularly if they fear self‑incrimination.

These rights help ensure that citizens are not unfairly coerced or detained in the course of providing information.

Interview Safeguards

While police can invite a witness to interview and ask questions, they must not detain or restrict their movement unless they have legal authority. If a person refuses to stay or answer, police may consider whether there are grounds to arrest on suspicion of an offence, but mere lack of cooperation as a witness does not justify detention.

Practical Scenarios

Recording a Witness Statement at the Scene

At a crime scene, police may stop and speak with bystanders or persons with relevant information. A person is free to leave after providing their name and address (or choosing not to assist), unless there are separate grounds to arrest them. Asking for cooperation does not amount to detention.

Inviting a Witness to a Police Station

Police may request a witness to attend a police station at a set time to give a statement. This is a voluntary attendance and the person is free to decline or leave the station at any point unless and until they are formally arrested.

Arrest Following a Voluntary Interview

If, during the course of a voluntary interview, evidence emerges that gives police reasonable grounds to suspect the person of an offence, they may arrest them and then detain them under the legal framework for suspects. At that point, detention must comply with PACE and statutory safeguards.

Common Questions

Can Witnesses Be Held at a Police Station Without Arrest?

No. Unless there is separate statutory authority (such as under terrorism legislation), police cannot detain a witness they have invited for questioning. Voluntary attendees have the right to leave at any time.

What Happens if a Witness Refuses to Attend an Interview?

Police cannot compel attendance without arrest powers. In practice, failure to attend may lead to reconsideration of the investigation and possible arrest if police believe there are reasonable grounds for suspicion. However, refusal alone does not equate to detention.

Do Police Have to Inform a Witness of Their Rights?

For voluntary attendees, police must explain that they are not under arrest and have the right to leave unless and until police decide to arrest them. For arrested individuals, detailed rights are provided under PACE and Codes of Practice.

Final Thoughts

In England and Wales, police do not have a general power to detain witnesses solely for the purposes of investigation. Witnesses may be invited to provide information or attend interviews voluntarily, but they retain the right to leave unless and until legal powers - such as arrest - are lawfully used. Arrest and detention require a reasonable suspicion of an offence and must meet statutory criteria under the Police and Criminal Evidence Act 1984, with procedural safeguards and time limits. Exceptional statutory powers may permit specific forms of detention in limited contexts, but these do not apply to ordinary witness interviews. Understanding these distinctions helps protect individual freedoms while allowing investigations to proceed lawfully.