Legal

Citizen's Arrest — Section 24A PACE

Any person may arrest for indictable offences under strict conditions.

Conditions

Offence must be indictable (theft, ABH+, criminal damage over threshold, etc.).
Offence has been committed OR is being committed.
Reasonable grounds to believe person committed it.
It is not reasonably practicable for a police officer to make the arrest.
AND one of: to prevent physical injury, damage to property, loss/harm to self or others, or to prevent escape before police arrive.

Making the arrest

Tell them clearly: they are under arrest, what for, why using this power.
Use only reasonable force.
Hand over to police as soon as possible.

What you CANNOT arrest for

Suspicion alone (police only)
Summary offences
Future offences

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