It was once accepted that creating an offence to produce an arrest constituted dodgy evidence. But as the forces of evil are not obeying many ground rules, the officers of the law can sometimes be forgiven for using some imagination when on a mission. In the old days aged ladies were not often beaten over the head with iron bars while shopping, and the use of knives, razors and guns were restricted to specific occasions such as Saturday night brawls and bank robberies. Now of course, being a shopkeeper, or even working in a large store, does produce the risk of becoming a target. Retailers are for this reason rather keen to organise protection through systems, equipment and the police. Ram raids, double-barrelled shotguns, stabbing instruments, coshes, clenched fists, threats, foul language, racist abuse, property damage, pilferage, burglary, counterfeit money, are now part of every-day retail life - not all of it on one day, but every new day brings a fair chance that a disturbing incident will colour those otherwise mundane moments. Not surprisingly, the Association of Convenience Stores has placed high on its list of priorities a practical programme to assist its fearful members. (Perhaps "fearful" should be spelt "fear full" to avoid misunderstanding). But some of them may be under threat from another source. Young glue sniffers, smokers and under age drinkers often buy their illicit enjoyment by presenting themselves boldly at the counter or checkout. The law says they must not be served. There is now a growing movement by trading inspectors to check the culpability of these shopkeepers by sending in test purchasers - boys and girls - who are watched as they spring the trap. There is of course a difference between serving a four-pack to a 17-year-old, six-footer with stubble, and a pimply-faced 13-year-old. No doubt the inspectorate chose their apprentices to be young enough to be noticed. But is such provocation justified? Identity cards should be introduced in spite of the opposition to them. That would stop all this nonsense.