Folding pocket knife

A folding pocket knife is a knife with a blade that folds into the handle. In England and Wales, the phrase matters 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 shorthand "legal pocket knife" is only partly accurate. A small non-locking folding knife may be outside section 139, but it can still be treated as an offensive weapon if carried or used for causing injury.

Section 139 Exception

Section 139 applies to articles with a blade or sharp point in public. It does not apply to a folding pocket knife unless the cutting edge exceeds 3 inches.

The key 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. The reason is practical: once locked, the blade is not immediately foldable at all times. A lock knife in public therefore usually needs a good reason or lawful authority, even if the blade is short.

Measuring the Blade

The statutory wording refers to the cutting edge, not necessarily the whole visible metal blade. A person relying on the exception should be able to explain the measurement clearly. If the blade is close to 3 inches, the practical risk of dispute increases.

Ordinary Uses

Small folding pocket knives are commonly used for ordinary tasks such as opening packaging, cutting string, fishing, camping, light repairs, or outdoor work. Ordinary usefulness is why the section 139 exception exists.

That does not mean carrying one is always sensible. Venues, workplaces, schools, courts, airports, licensed premises, private events, and transport operators may have their own rules or may be covered by stricter legal 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 rule. If a person is facing a serious attack, the law on self-defence and Reasonable force considers 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

• Criminal Justice Act 1988, section 139
• Crown Prosecution Service: Knife and other weapons offences
• House of Commons Library: Knives, offensive weapons and serious violence