A folding pocket knife is a knife with a blade that folds into the handle. In England and Wales, the phrase is important because section 139 of the Criminal Justice Act 1988 excludes a folding pocket knife from the public-place bladed article offence unless the cutting edge of its blade exceeds 3 inches.
The everyday phrase "legal pocket knife" is only partly accurate. A small non-locking folding knife may fall outside section 139, but it can still become an offensive weapon if it is carried or used for causing injury. The facts around possession, use, place and intent matter.
Section 139 Exception
Section 139 applies to articles with a blade or sharp point in a public place. It does not apply to a folding pocket knife unless the cutting edge exceeds 3 inches.
The usual points are:
- The knife must fold.
- The blade must not lock open.
- The cutting edge must not exceed 3 inches.
- The exception only concerns section 139. It does not excuse threats, assault, possession in restricted places, or intent to use the knife as a weapon.
Lock Knives
A lock knife is not usually treated as a folding pocket knife for section 139. Once locked, the blade is not immediately foldable at all times. A lock knife in public normally needs a good reason or lawful authority, even if the blade is short.
The Crown Prosecution Service guidance treats a folding pocket knife separately from other bladed articles, but it also makes clear that lock knives do not benefit from the simple pocket-knife exception in the same way.
Measuring the Blade
The statutory wording refers to the cutting edge. This is not always the same as the whole visible metal blade, because a blade may have an unsharpened ricasso or other non-cutting area near the handle.
A person relying on the exception should be able to explain the measurement clearly. If the cutting edge is close to 3 inches, the practical risk of dispute is higher.
Ordinary Uses
Small folding pocket knives are commonly used for ordinary tasks such as opening packaging, cutting string, fishing, camping, light repairs, gardening, food preparation outdoors, or other routine work.
Ordinary usefulness is why the section 139 exception exists. It does not mean carrying a knife is always sensible. Workplaces, schools, courts, airports, secure venues, premises with alcohol licences, private events and transport operators may have their own rules or may be covered by stricter controls.
When It Becomes Risky
A folding pocket knife can create legal risk where:
- The blade locks.
- The cutting edge exceeds 3 inches.
- It is carried for self-protection rather than ordinary use.
- It is displayed during an argument.
- It is used to threaten, intimidate or injure.
- It is carried into a school, court, airport, secure venue or other restricted place.
- Other facts suggest preparation for violence.
Self-Defence
Using a lawful pocket knife in self-defence is not judged by a simple checklist. If a person is facing a serious attack, the law on self-defence and Reasonable force looks at the circumstances as the person honestly believed them to be. A person under attack is not expected to weigh the exact measure of force with calm precision.
That is different from carrying a knife for possible future protection. General fear of being attacked is normally a poor reason for carrying a weapon in public. The distinction is between an item lawfully present for ordinary purposes and an item carried as a weapon from the start.
Practical Examples
Lawful Everyday Carry
A person carries a small, non-locking folding knife with a cutting edge under 3 inches for opening parcels and cutting string. On those facts alone, section 139 usually does not apply.
Same Knife, Different Intent
The same person tells friends they are carrying the knife in case they need to stab someone. The issue changes. The knife may become an intended offensive weapon because of the purpose for which it is carried.
Lock Knife
A person carries a locking folding knife in a jacket pocket while shopping, with no work or outdoor reason. The lock means the section 139 folding pocket knife exception is unlikely to apply.
Immediate Attack
A person is attacked by multiple people and uses an item already lawfully in their possession to escape or stop serious violence. The legal question may focus on reasonable force rather than ordinary possession, but the facts will be examined closely.
See Also
- Bladed articles
- Offensive weapon
- Self-defence in English law
- Reasonable force
- Criminal Justice Act 1988
References
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