The Criminal Law Act 1967 does not give you a blanket right to chase a fleeing suspect with a weapon. While Section 3 of the Act allows for the use of "reasonable force" to prevent crime or make a lawful arrest, using a weapon against a fleeing person is extremely likely to be deemed disproportionate, excessive, and illegal.
The Legal Position (Criminal Law Act 1967)
- Reasonable Force Only: Section 3(1) states: "A person may use such force as is reasonable in the circumstances in the prevention of crime, or in effecting or assisting in the lawful arrest of offenders or suspected offenders...".
- Proportionality is Key: The force used must match the threat. If a suspect is running away, they are generally not an immediate threat to you or others. Chasing them with a weapon implies a desire to harm or punish (revenge), rather than to stop a crime.
- Grossly Disproportionate Force: If you chase a suspect and use a weapon—especially if you cause serious injury—it will almost certainly be considered "grossly disproportionate," and you may face criminal charges, including wounding or assault, regardless of the fact that they stole from you.
What if I chase them as they run off?
This situation is different as you are no longer acting in self-defence and so the same degree of force may not be reasonable. However, you are still allowed to use reasonable force to recover your property and make a citizen's arrest. You should consider your own safety and, for example, whether the police have been called. A rugby tackle or a single blow would probably be reasonable. Acting out of malice and revenge with the intent of inflicting punishment through injury or death would not.
Chasing a fleeing suspect with a weapon and subsequently using it is highly likely to be considered
malice,
revenge, or
retaliation rather than self-defence in legal terms, particularly if the initial threat has passed.
(Source - CPS)