A retired detective who worked on the original police probe into the unsolved murder of sex worker Emma Caldwell has broken his silence on the “flawed” investigation.

In an exclusive interview with the Sunday Herald, Geoff Fisher said the failed bid to find the killer had been a “monumental waste of money” and blasted the former Strathclyde Police force for focusing on the wrong suspects.

He fears there is now “no chance” of a conviction and said of the police handling of the case: “Sketchy doesn’t even begin to cover it.”

Fisher also spoke of how the force’s scandal-hit Counter Corruption Unit (CCU) put him through "four years of torture" over alleged data protection breaches that the Crown Office is not pursuing.

Caldwell’s murder in 2005 triggered one of the biggest manhunts in the history of the old Strathclyde force, but the investigation has since become a byword for failure.

Picture: Emma

Senior officers wrongly believed four Turkish men were responsible for the Glasgow woman’s death and they mounted an elaborate bugging operation in a city café used by the men.

The suspects were charged but the case collapsed after serious concerns were raised about the quality of evidence gathered.

Revelations about the botched police probe, including the fact that a Scottish suspect had been repeatedly questioned, led to the single force launching a re-investigation last year.

Police Scotland has also been under fire for illegally spying on serving and retired officers they wrongly believed had leaked information to the media about the original Caldwell probe.

Fisher, who was a detective on the case, told the Sunday Herald he could stay silent no longer: "I'm speaking out because of the huge public interest and the way Police Scotland and the Counter Corruption Unit have been operating."

Fisher joined Strathclyde in 1983 and worked his way up to the Serious Crime Squad, which handled counter terrorism, Category A murders and issues relating to Special Branch.

The 50 year old was renowned for his skill in interviewing suspects and he worked on a number of cases involving Glasgow’s crime families.

“We were always asked to go to the trickiest murders. Anything involving organised crime groups ... we were involved.”

Fisher said of his job: “I loved it. I felt part of something. I knew that when something big came up, I would be the main focus of it. I would be involved, whether it was bursting witnesses [trying to get an admission] or interviewing the main suspect.”

On the Caldwell probe, he said his first involvement was when her disappearance was being treated as a missing person case.

“I recall being on duty and being sent to the Inglefield hostel to remove every item of clothing from her room. That was done and I knew that the inquiry had gone to Aikenhead Road CID. It was Operation Grail.

“I went on holiday and when I came back I noted that a body had been found.”

Fisher was not on the initial murder team trying to find the killer, but he said he believed the police work at that time had been excellent and paid tribute to Senior Investigating Officer Willie Johnston.

“The initial investigation by G Division CID was an exceptional investigation, a very intelligence-led operation. It was basically chapping the door of the person who I believe is responsible for this."

However, for reasons that have never been explained, he said the investigation went in a “totally different direction” and the focus switched from the Scottish suspect to the Turkish men - so called Operation Guard.

This was led by a different team of senior officers and the surveillance operation was put in place. “I was aware that the Serious Crime Squad had commenced Operation Guard, which was a covert investigation.”

At this point, his own services were called upon: “I was asked if I would come along and start doing some witness interviews,” he recalls.

In particular, he interviewed a number of Turkish men: “They were very very difficult interviews.”

However, despite the enthusiasm of the team in pursuing the Turks, Fisher believed “nothing substantial” was found and he was never convinced they were involved in the killing.

“In any murder enquiry, you always get a wee break. Not one witness, not one accused out of the four of them, gave one iota of evidence.”

On why the force pushed ahead with this line of enquiry, he said: “My impression was that it was an ego thing [for a senior officer]. It was the most expensive inquiry in Strathclyde Police. They wanted it to succeed.

“On the day of the big interviews, they were all watching and [a senior officer] was convinced I was going to get a burst. Every time I get an interview I'm convinced I'm going to get a burst. Not on this occasion.”

He says of Operation Guard: “Sketchy doesn’t even begin to cover it.”

Asked whether Strathclyde clung to this part of the enquiry because the force wanted a return for the money spent on the surveillance operation, he said: “110%.”

Fisher said of the Scottish suspect who had been overlooked: “My granddaughter could have written a compelling case that would have got him convicted.”

He added: “There was a 100% chance to convict somebody for that poor soul’s death and they didn’t do it.”

The case against the four Turks was dropped in 2008. Fisher recalled: “I wasn’t surprised in the slightest.”

He is frustrated about Operation Guard, but feels anguish for the victim and her mother.

“I just feel for her family that they didn’t get the proper result and the poor lassie has been dead 11 years. I just think it is sad.

“It was a monumental waste of money and it has not brought a satisfactory conclusion, nor any closure, to the Caldwell family.”

Fisher is also sceptical about the re-investigation: “I think it’s too late now. I really do.”

He explained: “In retrospect, they realised ‘shit, we have made an arse of this’ and spent public funds on a shitty intrusive surveillance operation at a Turkish café that brought nothing back.”

On the possibility of getting a conviction, he said: “No chance.”

Picture: Geoff Fisher

In August last year, the Sunday Herald revealed how the CCU, responding to leaks exposing Operation Guard, had unlawfully used its spying powers in an attempt to flush out any moles.

David Moran, a serving detective in the Murder Squad, was one of the officers wrongly suspected of being the leaker.

Fisher defended his former colleague: “They put two and two together and decided that Davie Moran was the leak. Davie Moran didn’t work on the inquiry.”

He added: “Davie is a great guy. A first class detective. I worked with him on the Gerbil murder case [the gangland killing of Kevin 'Gerbil' Carroll. [Leaking is] not Davie’s game at all. He has made a formal criminal complaint against Police Scotland and he will take that the full road.”

Fisher is also highly critical of the way Strathclyde and then Police Scotland pursued him over alleged data protection breaches in 2012.

“The CCU took me from my place of work, humiliated me, interviewed me, threw me out saying ‘you might hear about this and you might not’. Eventually I go to court for six charges under the Data Protection Act which are binned. It’s their way of saying ‘we can reel you in at any time’.”

Fisher said he had been put through “four years of torture” and was “thrown to the dogs”. He believes CCU should be abolished: “They have criminalised good cops. They have ruined people’s reputations. My reputation.”

After 30 years as a police officer, he retired in 2013 not knowing what the CCU probe would lead to. He said his last day was the “saddest day of my life.”

Recent years, he says, have been difficult: “I was ashamed. I went through various thoughts about whether I should continue on this planet. I felt I didn’t have a friend in the world.”

He eventually learned last week that the case against him had been dropped, but in a very twenty-first century way: “I found out on Twitter.”

Responding to Fisher's comments, Detective Superintendent David McLaren, who is leading the re-investigation for Police Scotland, said: "Since 2015 a dedicated team of detectives has been working on the re-investigation of Emma's death.

“A large part of our early work has involved detectives reviewing particular aspects of the original Police investigation."