Police Scotland has been ordered to pay a Scottish policeman-turned-novelist £10,000 in damages after being found guilty of abusing surveillance powers to hunt down sources who blew the whistle on a bungled murder enquiry.

The Investigatory Powers Tribunal published its judgment yesterday. Although five people filed claims against the force, just one was awarded damages.

The damages award is one hundred thousandth of the police force's £1,000,000,000 income for financial year 2015/16, as noted in the Scottish Police Authority's accounts.

Mr Justice Burton, president of the IPT, refused to award any damages to the other four claimants and even ordered that they should not be paid any compensation, despite acknowledging they, too, were unlawfully spied upon by police employees who authorised themselves to eavesdrop on them.

The murdered prostitute and the mysterious suspect who was freed

In April 2005 a Glasgow prostitute, 27-year-old Emma Caldwell, disappeared after leaving a hostel in the city. Her naked body was found concealed in woods by a dog walker, 64km (40 miles) away from the city. The post-mortem concluded she had been strangled. The then Strathclyde Police opened a murder investigation.

Two years later, four Turkish immigrants were arrested and charged with Caldwell's murder. In December 2007, however, they were freed after the prosecution said there was “insufficient evidence to proceed to trial.”

The four Turks had been bugged by police and Caldwell's family had been told that mistakes had been made in translating the tapes. Those mistakes, police told her grieving relatives, made it impossible to prosecute as the tapes contained the only truly incriminating evidence. The case then lapsed.

In 2013 a former policeman, Gerard Gallacher, learned that constables who had worked on the murder enquiry had had serious concerns about its handling. It appeared that a Scottish man had been interviewed by Strathclyde Police about Caldwell's disappearance seven months before the arrest of the Turks – and had even led detectives to within 65m (70 yards) of the spot where her body had been found. He was said to have told investigators that he found the location while looking for a dogging spot with Caldwell, and that they had driven there together on “five or six occasions”.

It was said that the police interviewing this man came to believe that he was Caldwell's murderer. However, senior officers ordered him to be released and for that line of enquiry to be closed.

The witch-hunt

Gallacher spent two years digging into the case and contacted the media with his findings. Ten years to the day after Caldwell's disappearance, the Scottish Sunday Mail began publishing fresh stories about her murder. Very shortly afterwards, the Scottish Crown Office ordered Police Scotland to reopen the murder enquiry.

On 7 April 2015 – just two days after the first of three Scottish Sunday Mail stories appeared in print – Police Scotland's Counter Corruption Unit opened a secret criminal investigation. The fingermen believed that the only way the newspaper could have learned about the bungling of the decade-old murder case was if current or former police employees had talked to journalists about the case – a serious crime, in their eyes.

A “Mr Stitt” of the CCU asked another Police Scotland employee, Detective Superintendent David “Davie” Donaldson, for advice on how to get his permission, under sections 21-25 of the Regulation of Investigatory Powers Act, to spy on Gallacher and the people he was talking to. Donaldson gave Stitt that advice – and then rubber-stamped Stitt's application. The IPT found that Stitt had not taken Donaldson's advice on board in his written application, yet Donaldson gave him the green light anyway. This authorised the CCU to intercept and record nine people's “communications traffic data” over 32 days.

The justification that Stitt gave to Det Supt Donaldson was:

Gallacher is being provided with information from persons who fit the criteria … [of being an officer who worked directly on the investigation, or with access to police systems containing information about the investigation] which is thereafter being passed to journalists involved.

The Interception Of Communications Commissioner's Office steps in

IOCCO discovered what Police Scotland had done during its annual review of the force's use of RIPA authorisations. In its report on the police abuse of their powers, quoted in the IPT judgement, IOCCO condemned Police Scotland, saying:

The clear purpose of these applications was to determine either a journalist source or the communications of those suspected to have been acting as intermediaries between a journalist and a suspected source. This purpose was clear on the face of the applications.

This is against the law. In fact, the practice of police employees ticking an internal police form allowing them to abuse anti-terror powers for spying on journalists and their suspected sources in order to punish whistleblowers was specifically made unlawful in March last year. Now, police must at least get a magistrate to rubber-stamp such spying warrants.

A senior police constable, Detective Superintendent Brenda Smith, had sent an email round Police Scotland in February 2015 drawing attention to the new requirements. The IPT found that this was enough to ensure the force was aware of the requirement to follow the new code of practice.

IOCCO's final report into the matter did not conclude that Police Scotland had intentionally broken the law but did concede that they might have been “reckless” about obeying it.

Damned by their own fervour

In stating the facts in his judgement, Mr Justice Burton said: “[Police Scotland] made no sufficient attempt to assess the proportionality in all the circumstances of seeking to access communications data in support of that enquiry,” and added: “The Respondent had no coherent view as to what, if any, crime might have been committed by any person. It nonetheless determined to seek to acquire the communications data it desired by using s.22(2)(b) of RIPA.”

Damningly, the judge also found: “The Respondent had no intelligence case suggesting that the Claimant [Police Scotland] was involved in the disclosure of material to Mr Gallacher, not even that he had access to the material thought to have been disclosed. It nonetheless resolved to seek to acquire his communications data.”

The shame of public knowledge is punishment enough for law-breakers. Slap us on the wrist, said Police Scotland

Jeremy Johnson QC, the barrister acting on behalf of Police Scotland, argued before the tribunal that there was no case for compensation to be awarded to Gallacher and his wife – who were, by that stage, the only two out of the five complainants seeking monetary damages.

In the police's view, merely declaring that Police Scotland had broken the law by infringing the claimants' human rights – namely, breaching the European Convention on Human Rights' guarantees on the right to a private life and to freedom of expression – would amount to “just satisfaction”.

The judge mostly agreed with this, declaring that an independent police force should investigate the whole spying matter but did award Gallacher alone £10,000 “to reflect the stress he has suffered and his loss of earning capacity” as a result of the unlawful CCU investigation.

Durham Police will investigate the complaints against still-serving Police Scotland employees who were involved in the witch-hunt. Police Scotland also gave the IPT an undertaking that it would “provide a reasoned decision on the determination of the investigation.” Mr Justice Burton ordered that Police Scotland could retain the data it had gathered until the investigation and any related legal cases were completed, unless a complainant wrote to them asking for their data to be deleted.

Det Supt Donaldson has since retired from Police Scotland. He refused an order to appear before the Scottish Parliament to answer questions about his involvement in authorising the CCU witch-hunt.