It is a great benefit of living in the UK that guns are not perceived as a day-to-day threat in most communities.

The same cannot be said for knives. Knife crime has been a blight on Scottish cities, towns and villages for far too many years. Something had to be done and stop-searches by the police to uncover knife-carrying, while not a panacea, have certainly helped. The tactic, championed by Chief Constable Stephen House, has contributed to a 50% drop in violent crime in Strathclyde since 2007.

Yet stop-searches must be used within the law as part of intelligence-led policing. Instead, there are worrying signs that some officers might not have understood that message amid the general atmosphere of enthusiasm for the policy within Police Scotland.

In order to carry out a search, officers must have probable suspicion that an individual is involved in criminal activity. Mr House spelled this out in April when he said: "There is nothing to fear from stop-and-search. My officers will target known knife-carriers and violent offenders, and be visible and conduct searches in the areas where the community tell us there is likelihood of violence, disorder or knife-carrying."

Yet while the management of Police Scotland may understand that stop-and-search should be used only within certain parameters to tackle violent crime, it appears that not all officers do. A memo seen by The Herald and issued by an inspector to Glasgow divisions told officers to use overtime "solely for the purpose of targeting stop searches" and that "NIL returns are not acceptable under any circumstances". This sort of pressure carries clear risks: of encouraging officers to stop and search individuals on flimsy grounds or without any real cause; of taking up a disproportionate amount of police time that might be better spent on other activities; and, as time goes on, of alienating those individuals who are searched and found to be innocent, especially where a person finds themselves subjected to a search more than once.

Police Scotland has made clear there are no targets for stop-and-search activity, and that this memo arose from a genuine misunderstanding. Fair enough. Yet it suggests efforts are required to ensure that all officers understand the need to deploy stop and search "on an intelligence and analysis led basis and in an ethical manner".

For stop-and-search is under scrutiny. The growing use of the policy in Scotland has been causing concern for some time. The law is different in England and Wales, but the fact that only one million stop searches are carried out south of the Border each year compared to 186,463 in Scotland in three months alone, is highly suggestive. Stop and search has proven itself in crime prevention. While it produces results and helps lower crime rates, public criticism is likely to remain muted, but it is crucial the policy does not become discredited by being overzealously applied.