THE Scottish Police Federation (SPF) has defended non-statutory stop and search operations by trying to link the controversial frisking policy to the solving of the notorious World’s End murders.

In a briefing on stop and search, the officers' staff association printed the pictures of the two teenagers killed by Angus Sinclair and argued that his conviction hinged on consensual policing - like citizens agreeing to be frisked. Sinclair was convicted on the basis of DNA evidence.

In its first year, Police Scotland recorded over 500,000 frisks north of the border, a volume proportionately far higher than any other part of the UK.

The majority of the searches were non-statutory, which means they have no basis in legislation and rely on the supposed consent of the individual.

This practice is not used by police officers elsewhere in the UK.

However, after it was revealed that non-statutory searches had been conducted on young children and even babies, First Minister Nicola Sturgeon announced that QC John Scott would head a review that would consider abolishing the tactic.

At the same time, Police Scotland confirmed there was now a “presumption” against non-statutory searches.

The issue arose again last week after a United Nations committee called for the policy to end.

The SPF, which represents every constable, sergeant, inspector, chief inspector, police cadet and special constable in Scotland, has been critical of a target-driven approach to searches and the “large scale” use of frisks.

However, in its latest briefing, the SPF warned against abolishing the non-statutory frisks in their entirety.

In a section on “consent”, the staff association argued: “The solution(s) to the brouhaha over what has become known as stop and search will not be ‘fixed’ by introducing the frankly illiberal proposals to remove the ability of the public to cooperate with the police.

“The ability of the public to cooperate with the police should be entirely unfettered by the legislature."

Under pictures of Helen Scott and Christine Eadie, who were murdered by Angus Sinclair in 1977, the briefing stated: “If we consider for a moment that the recent conviction for Angus Sinclair for the Worlds End murders was ultimately as a consequence of a voluntary DNA sample, this should serve as a timely reminder that actively prohibiting police/public co-operation will result in serious crimes not only going unpunished but also undetected.”

Sinclair was eventually brought to justice in 2014 - some 37 years after the killings.

The SPF also stated: “Countless quantities of controlled (illegal) drugs have been seized using consensual searches and many criminals have been imprisoned and their illicit profits seized. Firearms and many thousands of pounds have also been seized from those involved in serious and organised crime.”

Hugh Henry, who is Scottish Labour’s shadow justice secretary, said: “The volume of searches is out of hand and the fact that so many people are searched compared to other parts of the UK makes you wonder if the policy is target driven. I believe stop and search has a place, but the rules and parameters have to be agreed and Police Scotland must work within those rules.”