THE illegal spying operation linked to the unsolved murder of Emma Caldwell is one of the grubbiest episodes in Police Scotland's short and far from less illustrious history.

After the press exposed the failings of the original Strathclyde Police investigation into the young prostitute’s killing, the single force should have read the media coverage carefully and immediately ordered a fresh manhunt.

Instead the Counter Corruption Unit embarked on a mole-hunt that involved seizing the mobile phone data of serving and retired officers suspected of involvement in the leak.

However, not only were the suspicions entirely groundless, but the snooping operations were unlawful.

The illegal spy applications led to Holyrood hearings, triggered an Investigatory Powers Tribunal and produced grovelling apologies to the individuals wrongly targeted.

Two points about this farce need to be made. The first is that the fallout from this scandal has been a huge distraction from the real issue of finding Caldwell’s killer.

A vulnerable woman was murdered, but when flaws in the original investigation were made public Police Scotland focused on the leaks. This was unforgivable and has led to an enormous amount of energy being directed on a side issue.

The second point is the treatment of the serving and retired officers. David Moran, who we interviewed today, was a highly respected detective who was treated appallingly by the force.

If this is how the force treats one of its own, how does Police Scotland behave towards ordinary members of the public? The CCU has behaved disgracefully - and it is time the officers responsible were held to account.