When we buy from a reputable high street store, we trust the integrity of the store to sell goods that don’t have the potential of being illegal when we leave the store. The paradox here is the fact that selling is legal but possession is illegal. The lock knife is bought by decorators, electricians, campers and a multitude of other members of the public who do not know that possession in a public place is illegal.

Dealing with cases as an expert witness, I have had reason to buy lock knives from leading stores that are perfectly described in statute as prohibited weapons. In one case the defendant was going home with a few bits and pieces in a carrier bag, including a lock knife. He told police he was going home to do some decorating – he received a custodial sentence. The Home Office perspective is that it is not illegal to sell lock knives, but it is clear that possession in a public place is a different matter. Some stores even include ‘lock knife’ on their till receipts, no doubt prima facie evidence that the item is a lock knife, and invaluable in proving a case against someone who has the receipt with them.

Section 139 of the Criminal Justice Act 1988 aptly describes the lock knife as: ‘A folding knife which is secured in an open position by a locking device and can only be released from the open position by the pressing of a release button.’ A while back I asked the Home Office to clarify any ambiguity arising from whether or not a lock knife was illegal under this statute and it replied: ‘It is an offence to possess "lock knives" in a public place, irrespective of whether the blade is actually locked open at the time.’

There are few ways to explain yourself out of lock knife possession in a public place. Unlike ‘reasonable excuse’ in the Prevention Of Crimes Act 1953, you have to show ‘good reason’ (section 139 of the 1988 act), which has a much tighter interpretation. Saying that you forgot it was there is no excuse. You could say that you use it in your work, but even this explanation will not vindicate you – after arrest it will be a matter for the courts to decide. Finally, there is no way you will convince a court that your lock knife is a religious instrument or part of your national costume.

Gang problemWoolworths disclosed last year that the utility knife (lock knife) it then sold complied with all relevant trading requirements, and that it had strict under-age purchase procedures. This is admirable, but the word on the street is that this type of ‘utility knife’ is becoming the ideal gang weapon. It is easy to purchase, compact and easy to conceal, has a very sharp replaceable blade that can be disposed of after ‘use’, and locks firmly in place.The reality is that there is a greater chance of the police arresting the respectable citizen who has innocently purchased such a knife from a reputable store, because they will have a more overt approach to its possession. The streetwise gang member knows the legal situation and has a number of covert methods for keeping such a knife out of sight until needed.

Let’s just recap before we lose sight of the paradox in this legislation. Stores can legitimately and legally sell lock knives to the public, but having them in a public place is an arrestable offence. Is it me, or does something have to be seriously re-examined?

Mike Finn, a former police officer and an expert witness on weapons, martial arts and violent crime, is director of consultancy for Elite International and principal of the Combative Science Institute