Special report: How detectives caught Karen's killer with incredible speed
Even in a city hardened to serious crime, the murder of the young Irish nurse was shocking
It's no surprise that the hard, gritty streets of Glasgow have proved the inspiration for so many top crime dramas. 'Taggart' and 'Cracker' all owed their popularity to the harsh realism drawn from a Scottish metropolis that survived decline from the second city of the British Empire, to savage Luftwaffe bombing raids and the no-less-damaging closure of the shipyards, mines and steelworks that once underpinned its wealth.
Combined with grinding poverty and sectarian rifts that often bubble under the surface, it sadly left Glasgow no stranger to violent crime.
In 2012, Glasgow ranked only behind Amsterdam for the highest rate of murders in Western Europe at 3.3 per 100,000 of population.
Billy Connolly even joked about the so-called 'Glasgow Kiss' or head-butt.
One Irish journalist, during a press conference about the Karen Buckley (24) murder investigation, asked about the relevance of a knife recovered by police divers from a Glasgow canal.
To the laughter of Scottish journalists, the reporter was asked did he realise just how many knives are found when even one stretch of a Glasgow canal is dredged?
This demanding heritage has produced a police force widely considered one of the finest, not just in the UK, but in Europe.
Police Scotland is particularly renowned for its embrace of hi-tech investigative techniques and the number of detectives with murder probe experience. This was a realisation that would only dawn on calculating murderer Alexander Pacteau (21) when two Police Scotland detectives knocked on the door of his Dorchester Avenue flat just 36 hours after petite Irish student, Karen Buckley, vanished from the popular West End nightclub The Sanctuary.
Pacteau, a fan of the 'Breaking Bad' crime series, discovered to his cost that Glasgow police are exceptionally good at what they do.
Even in a city hardened to serious crime, the murder of the Mourneabbey, Co Cork nurse was truly shocking.
The cruelty of the killing, added to the horror over how Karen's body was dumped in a barrel of caustic soda, brought thousands of Glaswegians on to the streets of George Square in an emotional gesture of solidarity.
Despite its tough reputation, Glasgow is also a city with a warm heart - a place where family is cherished, where students revel in a vibrant nightlife, where locals are deeply proud of their River Clyde metropolis and where city authorities work overtime to promote a tourist trade against the magnet just one hour away that is Edinburgh.
The true horror of Karen's death - and the contemptible manner in which Pacteau tried to dispose of her body - was borne out by the admission of veteran Detective Superintendent Jim Kerr that he had never encountered a case like it.
Det Supt Kerr, who led the investigation, was singled out for praise by Karen's parents, John (62) and Marian (61), because of the incredible speed with which his team traced Pacteau and then compiled such an overwhelming case against him that he pleaded guilty to the killing at the first opportunity.
The heartbroken parents slated Pacteau as a "cowardly, vicious criminal" who deserves to spend the rest of his life behind bars.
"Our hearts are broken at the thought of Karen's final moments on this world. The thought of her being alone, frightened and struggling for her life haunts us," Mr Buckley said.
"The panic and fear she experienced as she fought for her very survival, but she had no chance against that coward. The last face she saw and the last voice she heard was of that cold-blooded, cowardly murderer, who calmly set about trying to dispose of her body so she would never be found."
Pacteau signed a guilty plea to murder before the Honorable Justice Lady Rae in Glasgow's High Court last Tuesday. He now faces a life sentence, with the minimum term to be determined on September 8.
In truth, the Police Scotland investigation that brought the 6ft 4 former grammar schoolboy to justice was worthy of the finest of 'Taggart' episodes.
Scotland's Lord Advocate, Frank Mulholland QC, admitted that the police had "thrown everything they had" at the investigation.
A team of over 100 detectives were working the case within 24 hours - and they got their major break on the very first day.
Pacteau was confirmed on CCTV security camera footage as being the last person to speak to Karen at 1am on April 12 as she left the nightclub and walked on to Dumbarton Road.
It's worth noting that detectives trawled through over 1,200 hours of CCTV footage and were able to pinpoint Pacteau's movements almost to the minute from 1.06am/1.18am on April 12 when Karen was murdered, right through to April 15 when he was taken into custody.
At 6pm on April 13 - just hours, it would transpire, after Pacteau had dumped Karen's body on an isolated Glasgow hill farm - Detectives Chris Sneddon and Alex Ward were knocking on his door.
Pacteau opened the door and they were greeted by an overwhelming smell of bleach. Pacteau, in the first of his "tissue of lies", told them: "I was just calling to see you."
His explanation of why Karen had called to his flat didn't impress the officers.
They noted his mattress did not fit the bed frame.
It would later emerge that Pacteau, having failed to wash Karen's blood from the original mattress, had burned it on High Craigton Farm, some 7km from the city.
The two officers also noted odd items in the bedroom, including a toolbox, a roll of parcel tape and nail brushes.
Pacteau was brought to Helen Street police station in Govan for questioning as a witness - but forensic scientists Amanda Pirie and James Hawkins immediately moved into his flat under the supervision of Detective Alan Storer. Pacteau was told to go temporarily to a hotel and he checked into the Holiday Inn.
Police Scotland forensic experts would later confirm the presence of Karen's blood in both the bedroom and bathroom of Pacteau's flat, despite his use of bleach to wash the evidence away.
When he was questioned at Helen Street, Pacteau was found to have two padlock keys in his trouser pocket, together with a Poundstretcher receipt for caustic soda.
A special Police Scotland cadaver dog, trained to react to the scent of bodies, became agitated near the boot of Pacteau's Ford Focus car.
Another forensic expert, Prof Lorna Dawson of the Hutton Institute in Aberdeen, matched soil samples from Pacteau's Ford car to Dawsholm Park, where Karen's handbag was dumped, and to High Craigton Farm where her body was later recovered.
Despite Pacteau having cleaned his car and then taken it to Anniesland Valet for another cleaning, traces of Karen's blood were found on the passenger side.
Forensic experts even found Pacteau's fingerprint on the 220-litre blue plastic barrel he had filled with caustic soda in an attempt to destroy her body.
His phone showed he had researched the chemical properties of caustic soda at 8am on April 12. CCTV camera footage was traced of him buying caustic soda, drain unblocking fluid and padlocks from Tesco, Poundstretchers and Asda.
There was almost a twist in the investigation: Karen's handbag was found dumped by a council bin at Dawsholm Park at 7am on April 12 by a member of the public.
The person who found it decided to steal Karen's mobile phone - and wiped it of all calls and texts, unwittingly destroying evidence that might otherwise have been crucial.
When the individual realised the significance of the bag later that day, they contacted police.
On Wednesday, April 15, Pacteau was arrested as a suspect and admitted killing the University of Limerick graduate, initially claiming self-defence. Two days later, on April 17, he was formally charged with murder.
But the Police Scotland investigation continued to escalate, and on April 21, police divers located the heavy 30cm spanner that Pacteau used to bludgeon Karen to death from the murky waters of the Forth and Clyde canal.
On April 27, forensic experts finally confirmed that a mattress found burned at High Craigton Farm was from Pacteau's bedroom. Such was the efficiency of the police probe that they even traced a Tesco shop assistant who recalled Pacteau asking about a cleaning product to remove blood.
From Alexander Pacteau's point of view, his attempts to evade justice were a bungling failure.