Drinking in Aberdeen just got a whole lot more complicated, as police warned those popping out for a swift half that they may need to undergo drug testing before they are served.

In Lancaster, police were last week setting up scanners near the central bus station to check passers-by for knives. Meanwhile, on Waterloo station, sniffer dogs that will check you out for drugs or bombs – but not knives – have become a regular part of the daily commuter experience.

Welcome to the world of preventive policing. This, as Catholic readers may recognise, is one in which you may be penalised not just for the sins you have committed, but also for ones you are about to commit, or may just casually have thought about committing.

In Aberdeen, pub-goers will soon be faced with The Itemiser (pdf) - also known as the Ion Detector. This device can detect traces of drugs - including cocaine, cannabis, heroin and ecstasy - from hand swabs in a matter of seconds, flashing up green, amber or red according to what it thinks may be present.

Green will get you straight into the pub or club: amber means you will receive a drug information pack; red may result in your being refused entry, and possibly searched.

The test is voluntary, but customers will be refused entry if they do not take part. Or, given the police track record with knife-related stop and searches, it is just possible that a refusal to agree to being checked would itself be grounds to search you. After all, if you have nothing to hide...

Similar hijinks have been going on recently in Lancaster, as police and the Lancashire County Council’s Safer Travel Unit began stop and search procedures on members of the public travelling to and from Lancaster bus station.

This ‘Gateway Check’ involved the use of two airport-style metal detectors and handheld metal detectors, along with the frisking of travellers as they left the station.

One officer explained: "Due to recent anti-social behaviour and knife crime on buses we are trialling this method as an attempt to deter knife crime, we are currently randomly searching every fifth person."

Historically, police powers to stop and search have been limited to instances where there is reasonable suspicion that they might find something you shouldn't have on you: stolen goods, drugs, an offensive weapon, any article made or adapted for use in certain offences (for example a burglary or theft), knives, or items which could damage or destroy property.

Over the last few years, that limit has been seriously eroded. Section 44 of the Terrorism Act 2000 allows arbitrary stop and search with the purpose to prevent terrorism when authorisation is given by a commander of Metropolitan Police. This builds upon section 60 of the Criminal Justice and Public Order Act 1994, which permits searches for offensive weapons or dangerous instruments when authorisation by an officer of the rank of inspector or above is given in relation to a specific place and time period.

In general, court rulings have tended to uphold those powers, rather than diminish them - so even if you have done nothing wrong, failure to comply with a police search may now be an offence in itself.

Reports from locations as far apart as Wellingborough, North Wales and Ipswich all suggest that this is an approach to policing that is increasingly finding favour with police across the country.

Meanwhile, the issue of surveillance on railway stations can be attested to by Reg staff, who regularly brave the sniffer dogs of Waterloo in their journey to work each morning.

For once, we haven’t asked the police to comment on the above. We could reasonably expect some canned statements about the need to reduce risk, increase public safety, and further explanation that if we haven’t done anything wrong, we would have nothing at all to fear.

Instead, we will repeat a comment made by Head of the Police Improvements Agency, Peter Neyroud: Peter Neyroud, chief executive of the NPIA. In a Policing paper earlier this year, he and his fellow authors argued that "factual questions about the effectiveness of new technologies... in detecting and preventing crime should not, and cannot, be separated from ethical and social questions surrounding the impact which these technologies might have upon civil liberties".

In the end, these measures will either become an acceptable everyday part of British policing, or they will thoroughly alienate Police and public. Only time will tell. ®