The necessity test for arrest (ID COP PLAN)

The six reasons in PACE section 24(5) that make an arrest necessary, how Code G applies them, and the mnemonic recruits use to recall them.

The expansion

I: investigation, prompt and effective, of the offence or the person's conduct
D: disappearance, to stop a prosecution being hindered by it
C: child or other vulnerable person, to protect them from the person
O: obstruction of the highway, to prevent it
P: physical injury to the person or anyone else, to prevent it
P: public decency, to prevent an offence against it
L: loss of or damage to property, to prevent it
A: address, to ascertain it
N: name, to ascertain it

What it is for

Suspicion of an offence is not enough to arrest. Section 24(4) adds a second limb: reasonable grounds for believing arrest is necessary for a reason in section 24(5). ID COP PLAN is the order in which recruits memorise those reasons so they can name one at the point of arrest.

This is training shorthand; the test it stands for is in PACE section 24(5) and Code G paragraph 2.9. No College of Policing or force document using the mnemonic could be read on 19 October 2026.

Where it comes from

Section 24(5) of the Police and Criminal Evidence Act 1984 lists the reasons: "(a) to enable the name of the person in question to be ascertained"; "(b) correspondingly as regards the person's address"; "(c) to prevent the person in question" causing or suffering physical injury, causing loss of or damage to property, committing an offence against public decency, or causing an unlawful obstruction of the highway; "(d) to protect a child or other vulnerable person from the person in question"; "(e) to allow the prompt and effective investigation of the offence or of the conduct of the person in question"; "(f) to prevent any prosecution for the offence from being hindered by the disappearance of the person in question."

Code G paragraph 2.1 states that "A lawful arrest requires two elements": suspected involvement in an offence and "Reasonable grounds for believing that the person's arrest is necessary". Paragraph 2.9 repeats the criteria with examples; they "are exhaustive". Note 2C: the officer "is not required to be satisfied that there is no viable alternative to arrest" but should consider arrest "the practical, sensible and proportionate option". Note 2F: if voluntary attendance for interview is practicable, "arrest would not be necessary".

When it is used

At every arrest without warrant by a constable. Code G paragraph 2.2 requires the arrested person to be told the circumstances of both elements, so the reason is said out loud at the time.

Read on this site

Sources

Last updated 19 October 2026. Reviewed 19 October 2026