Understanding the police “necessity to arrest” test is crucial if you are being investigated for a criminal offence in England and Wales. Many people assume that if the police suspect you of a crime, they will automatically arrest you. That is not the case.
Under criminal law in England and Wales, police officers must justify an arrest by showing it is necessary. In many cases, instead of arresting a suspect, officers may invite them to attend a voluntary police interview under caution.
This guide explains:
What the legal “necessity to arrest” test is
When the police can lawfully arrest you
When a voluntary interview is more likely
Your rights during a police investigation
Why obtaining free and independent legal representation is essential
The power of arrest without a warrant is governed by Section 24 of the Police and Criminal Evidence Act 1984 (PACE).
Police and Criminal Evidence Act 1984
Under PACE, a police officer may arrest someone without a warrant if:
They have reasonable grounds to suspect that person is committing, has committed, or is about to commit an offence; and
The arrest is necessary for one or more statutory reasons.
This is commonly referred to as the “necessity criteria” or “necessity to arrest” test.
An arrest is unlawful if the necessity test is not satisfied — even if there is reasonable suspicion.
The Statutory Necessity Criteria (Section 24 PACE)
Police must believe arrest is necessary for at least one of the following reasons:
1. To Ascertain Name or Address
If:
The officer does not know your name or address
They reasonably doubt the name or address given
2. To Prevent:
Physical injury to yourself or others
Damage to property
An offence against public decency
Unlawful obstruction of the highway
3. To Protect a Vulnerable Person
Where arrest is required to safeguard:
A child
A vulnerable adult
4. To Allow the Prompt and Effective Investigation of the Offence
This is one of the most commonly relied upon grounds. Police may argue arrest is necessary to:
Conduct an interview under caution
Secure or preserve evidence
Prevent interference with witnesses
Prevent collusion with others
Seize digital devices (phones, laptops)
5. To Prevent Disappearance
If officers believe you may fail to attend voluntarily or abscond.
What Does “Prompt and Effective Investigation” Mean?
This phrase is often central in criminal defence cases. Courts have made clear that arrest must not be used as a matter of routine.
If:
A suspect is cooperative
Their identity is known
They are willing to attend a voluntary interview
There is no risk of interference or disappearance
Then arrest may not be necessary.
Improper use of arrest powers can lead to:
Claims for unlawful arrest
Claims for false imprisonment
Breach of PACE challenges
What Is a Voluntary Interview Under Caution?
Instead of arresting you, the police may invite you to attend a voluntary police interview.
A voluntary interview is still conducted under caution, meaning you will hear:
“You do not have to say anything, but it may harm your defence…”
Although you are not under arrest:
The interview is recorded
It can be used as evidence in court
You remain a suspect
The police can still arrest you later
When Will Police Consider a Voluntary Interview?
Police are more likely to offer a voluntary interview where:
The offence is non-violent
The suspect has a fixed address
There is no urgency
There is no safeguarding risk
The suspect has engaged through a solicitor
The investigation involves historic allegations
It is a first-time allegation
Examples often include:
Allegations of fraud
Historic sexual offence allegations
Workplace misconduct
Minor assault allegations
Harassment allegations
Theft investigations
A voluntary interview avoids the need for detention in custody and can demonstrate cooperation.
Key Differences: Arrest vs Voluntary Interview
| Arrest | Voluntary Interview |
|---|---|
| You are detained | You attend by agreement |
| Taken to a police station | Attend at arranged time |
| Subject to detention clock (24 hours+) | Free to leave unless arrested |
| Search powers triggered | Limited immediate powers |
| Biometrics may be taken | Usually no custody processing |
However, both situations carry serious legal consequences.
Can You Refuse a Voluntary Interview?
Technically yes. But refusing may result in:
Arrest on necessity grounds
Police obtaining a warrant
Inferences being drawn
Legal advice is essential before making that decision.
Common Misconceptions About Police Arrest Powers
“If I’m innocent, I don’t need a solicitor.”
False. Innocent people are prosecuted every day due to poorly handled interviews.
“Voluntary interview means it’s minor.”
Not necessarily. Serious offences — including sexual offences — are often dealt with voluntarily.
“If they wanted to arrest me, they would have.”
Police may delay arrest strategically.
The Importance of Free and Independent Legal Representation
Whether you are arrested or invited to a voluntary interview under caution in England and Wales, you are entitled to free and independent legal advice.
This is one of the most important rights you have.
A specialist criminal defence solicitor can:
Contact the police before interview
Obtain disclosure of evidence
Challenge the necessity to arrest
Advise on whether to answer questions, provide a prepared statement, or exercise your right to silence
Protect you from self-incrimination
Ensure PACE compliance
Prevent oppressive questioning
Safeguard your future
Legal representation at the police station is free of charge, regardless of income. It is completely independent of the police.
Attending a police interview without a solicitor is one of the biggest mistakes a suspect can make. What you say — or fail to say — can determine whether you are:
Released under investigation
Charged with a criminal offence
Released with no further action (NFA)
If you are facing a police investigation, arrest, or voluntary interview under caution, always insist on expert criminal defence legal representation. Protect your rights, protect your record, and protect your future.
