Inspector Darren McKie, who had locked up countless criminals during a successful ​21-year ​police career, watched as his ‘nagging’ wife Leanne died in front of him, throttling her with one hand and smothering her desperate attempts to scream for help with the other.

As her life ebbed away in front of his eyes, McKie destroyed what friends and neighbours had thought was the ‘perfect family’.

The cop had turned cold-blooded killer.

Darren McKie had just been promoted and was considered a rising star of Greater Manchester Police, where Leanne, who was a graduate and an only child, worked as a detective constable in the sex crimes unit.

The couple had three beautiful children and had just moved into a new £435,000 detached home - which was being extended and renovated at great cost - on Burford Close in leafy Wilmslow, one of Cheshire’s most sought after areas.

Yet, privately, their marriage had been creaking for years, groaning under the weight of their out-of-control spending, as they attempted to match the millionaire lifestyle enjoyed by neighbours in a suburb which is home to the super-rich.

Now, their children have no mother while their father is in jail, convicted of her murder following one of the most shocking trials in years.

Known as Spock by some colleagues because of his lack of empathy with others, McKie’s crime was all-the-more shocking because it appeared to be so cool and calculated.

Leanne McKie murder trial live: Jury sent out to consider verdict - this is the evidence they have heard over 12 days

When Leanne had found out he had been lying about the state of their dire finances, he went home early and strangled her - then set about trying to get away with what he hoped would be the perfect murder.

But his wicked crime and devious attempts to get away with it were exposed by a painstaking police investigation - and some bad luck.

Today McKie has been convicted of murder despite his denials.

Insp McKie, 43, inexplicably left his desk at Stretford police station - where he was in charge of resource management on the Trafford division - on September 28 last year, halfway through his shift.

Inside, he was probably quietly seething at an angry text message - calling him a ‘liar’ - that Leanne had sent him that morning, although none of his colleagues at Stretford police station had an inkling of his turmoil as he marched out of the nick with his rucksack.

Those colleagues weren’t to know about the crippling debt, the maxed out credit cards, the builders owed £60,000 - nor of the £54,000 loan he had applied for behind his wife’s back - forging her signature and hacking into her GMP account to get her latest pay-slip.

He hopped into his Audi and drove to the family home in Burford Close where he murdered his wife of 13 years.

McKie, a karate enthusiast, broke two bones in his wife’s neck when he strangled her. The force he had applied was equivalent to a karate chop, a pathologist would tell the subsequent trial.

Exactly what happened when he arrived home remains a mystery because McKie himself has refused to say.

Did he kill her in the kitchen? McKie was heard banging the drawers and vacuuming in the kitchen. Police believe he may have bundled her dead body into a cupboard under the stairs before calmly inviting a surveyor into their home to carry out a valuation.

In that case, McKie would have remained in the kitchen while the surveyor examined every room in the house... except that cupboard under the stairs.

Whatever the sequence of events, at some stage McKie reversed his wife’s Mini Countryman up to front door of their home and stuffed her slight, 5ft 2in body into the boot before parking the car round the corner.

Then, he coolly went out on the school-run, laughing and joking with other parents as he picked up the kids. Mum wasn’t home because she was working a late shift. Or so everyone thought.

With his wife’s body concealed in the boot of her car which he had parked nearby, he carried on as if nothing had happened. He put his kids to bed and then left them home alone while he drove around, looking for a suitable dumping ground for their mother’s body.

He had set about laying a false trail, sending texts to make it look like he thought she was still alive. In the last, sent at 9.20pm, he played the concerned husband.

"Hi hun. Your dad text me. They have not heard from you. You OK? Bit worried now. xx"

In his search for a makeshift grave, the murderer drove to a pond at Paddock Hill Lane in rural Mobberley, perhaps tempted by the ‘danger deep water’ sign he saw. But the pond was empty. Next he drove to Poynton Lake, where, under cover of darkness, he dragged Leanne from the car park about 140 metres to the edge of the water, where he left her face down.

He abandoned the car nearby, walking the eight miles back to the family home.

He thought he was committing the perfect crime. But he left behind telling clues which ultimately led to his conviction for murder.

As he walked home with his hood up, he was spooked by patrolling police officers - out and about trying to snare burglars - at around 1.15am. The officers wound down their window to speak briefly to him but allowed him on his way when he told them he was close to home, the first of very many lies he told police.

He continued his walk home but dumped his trainers, which were stained with blood from Leanne’s nose, in a wheelie-bin as he neared Burford Close.

Those same officers stopped him a second time at 2.15am - and noted he wasn’t wearing shoes this time. He refused to give his surname. He was forced to admit he was a cop when patrol officers spotted his police issue trousers.

McKie was driven home where the lying continued. The shocked patrol officers noted how McKie appeared ‘very cold, very emotionless and unmoved’ by the crying child who was waiting for him when he opened the front door.

He claimed to be worried because his wife had not returned from her late shift, although his calm and composed demeanour suggested otherwise. He reasoned he couldn’t drive as he’d drunk half of the bottle of Spanish red standing on the kitchen island. So he went out on foot instead, he said. He insisted he’d thrown away those trainers as they were ‘rubbing’ on his heel - another desperate lie.

The patrol officers left the McKie home to look for Leanne and her Mini, but to no avail.

McKie quickly put his clothes - which as a police officer he knew may well have collected evidence of his crime​ in their fibres - in the washing machine.

By complete chance, someone who had been out in Manchester and was worse for wear got off a bus and wandered towards ​Poynton Lake.

He got lost, and at around 3.45am, found Leanne’s body face down and ran from the woods, hyperventilating, to flag down a passing motorist. This was a key moment of fortune for the police - otherwise the body may have remain undiscovered for days.

Over the police radio, the grim discovery was relayed to the police officers who had escorted McKie back to his home, and so they were dispatched to Burford Close once more.

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There, they banged on the front door and woke the sleeping McKie. They stopped the washing machine mid-cycle. In his dressing gown, McKie was arrested on suspicion of her murder - and even then arresting officers noted that he remained ‘very calm and collected’.

Within a couple of hours, investigators had discovered the suspect’s blue New Balance trainers in a wheelie-bin.​ This was more good fortune for the authorities and bad luck for the killer - any longer and the bin would have been emptied and the trainers and key evidence would be gone forever.

Later, forensic experts would establish that the blood on them belonged to his wife.

The inspector claimed in interview he had never been to Poynton and didn’t even know it had a lake, but another expert concluded that soil found deep in the tread of those trainers came from Poynton Lake, not the garden of the family home.

His lies were quickly exposed.

Lying was something that came naturally to him, according to colleagues in GMP. He was viewed as quiet and inscrutable. He rarely invited chat about his family life. Some knew him as Spock, the Star Trek alien who struggles to feel emotion.

During his trial, McKie remained impassive throughout, taking notes in the dock and never once making eye-contact with his own parents, who dutifully attended every day to support their son.

One former police colleague said: “He was devious - wouldn’t think twice about telling bare-faced lies, just like in the trial.”

On one occasion, McKie is said to have allowed the entire shift under his control to clock off early when he was a sergeant. When his superior questioned him about it, he repeatedly denied it until he was told about CCTV footage which showed the officers leaving early. Only then did he admit what he had done.

Statements from friends and neighbours which were read out during the trial showed just how little they actually knew about the couple’s private struggles. Even before they married, he had somehow amassed his own debt of around £20,000. He had been in debt his entire adult life. The couple had once had to be bailed out by their parents to the tune of £91,000, including previous builders' debts. But still, the spending continued unabated, and the family outwardly enjoyed all the trappings of success, moving from one commuter suburb to another - from Sale, to Hale, and then finally Wilmslow.

Just ten months before the murder, McKie had told his wife ‘you hate me’, a claim she denied, during a series of heated exchanges via text about the move from their previous home at The Circuit in Wilmslow. Their move to Burford Close had two purposes: they were getting four bedrooms instead of three for their growing family and they managed to virtually wipe out​ their debt.

But, by then, their spending was out of control, regardless of how much they had reduced their debt.

In those texts, Leanne revealed she believed her husband thought she was ‘nagging’ or a ‘control freak’ when she asked about the family finances. He said ‘I knew it wouldn’t last’.

This picture of marital disharmony just wasn’t recognised by many of their friends.

One, Helen Baglin, told the trial: “Darren and Leanne appeared to have a brilliant relationship, and came across as a perfect united family... they were a lovely genuine couple who seemed to have a an amazing relationship.”

Another, Sarah James, said of the couple: “It seemed to me that they had the perfect family.”

But Leanne had been kept completely in the dark about the scale of the family’s financial problems and kept spending until her husband would tell her to stop, without ever explaining why.

She kept spending on her husband’s credit cards to pay for building work on the detached home on Burford Close, which they bought in February 2017 for £435,000 with the help of a £300,000 mortgage.

One builder was owed more than £17,000 and the balances on McKie’s credit cards topped £45,000 as part of a debt totalling more than £103,000 - not including the couple’s huge mortgage.

When they bought ​Burford Close in February 2017, their joint income of almost £68,000 (he earned £51,000 per year while his wife got £16,500 for working two days a week) was nowhere near covering all their bills.

The trial heard the couple were living ‘well beyond their means’ and after their bills had been paid they had just £84 left every month​ ​to pay for food and other essentials.

Regardless, the family splashed out £4,500 on ​​a​ one week holiday to ​The Algarve, ​Portugal that summer, and ​h​is Audi and her Mini Countryman had both been purchased on finance agreements.

An economic analyst told the trial that during the previous eight years the couple spent about £30,000 on holidays and flights, as well as about £70,000 at supermarkets. Some £12,846 of this was spent at M&S.

In 2017, on average, they were spending £58,000 more than they earned every month, with money being lavished on underfloor heating, granite worktops and top-of-the-range goods from The Bath Store to complete their dream home.

Leanne McKie, who would go to work with her DKNY handbag, liked the finer things, just like her husband.

While an extension was built, the family rented another home for £1,495 per month.

Leanne McKie, according to her husband, buried her head in the sand as the debt mounted. Police say this was simply not true - he never told his wife about the scale of their debt.

Unaware of their huge and mounting money problem, Leanne started an Instagram page dedicated to telling her pals about the unfolding renovation project at Burford Close.

Her final post came on September 27 last year, the day before her husband murdered her. It shows a picture of the front of their home which she says ‘looks so untidy’. Shutters for the windows ‘are on order’, she writes, joking that her family ‘look like the clampets!!’

The family had moved in just eleven days earlier, as she revealed in another post which showed a celebratory Domino’s pizza and a bottle of Prosecco.

She was to be killed by her own husband the day after her final post, after she had opened a letter about a £54,000 loan her partner had applied for behind her back.

It was just one of a series of desperate applications Darren McKie had made to loan companies and high-interest pay-day lenders as their builder sought the money he was owed.

Police believe he had forged her signature to make these applications - most of which were turned down - and even persuaded his wife to hand over her work log-in so he could get a payslip to back up the £54,000 loan application he made without her knowledge.

But, when DC McKie opened the Fluent Finance letter on the morning of September 28, she realised her husband was up to something.

Furious, she texted her husband: “You liar! Just got back a loan application with my passport and my name. Wtf.”

She looked at the search history of her iPhone, which was linked to her husband’s iPhone, and realised he had searched ‘Fluent Money’ on the internet.

She sent another angry text: “I asked you and you promised. Fluent finance? Who are they? Are we in such a mess? Why again? The kids need clothes and shoes what’s going on.”

The letter opened up an old sore for Leanne McKie. The family had been in financial trouble in 2013, only to be bailed out to the tune of £80,000 by their parents.

A flurry of calls she made to her husband that day went unanswered, even though his colleagues could see he was distracted and playing with his phone during a meeting. He had seemed distracted for weeks, although no-one knew the cause or how serious his problems were.

Without telling anyone, he picked up his rucksack and walked out of Stretford police station, committing a crime that shocked police and public alike.

A huge police investigation uncovered no gambling problem or extra-marital affairs - the background to this crime was simply the family’s spending and huge debt. Despite the evidence against him, despite knowing the police and prosecutors' ability to unravel killers' lies, McKie clung to the hope he would get away with it until the very end.

In his defence case statement - the document in which an accused person lays out their case - he claimed that after they argued for the last time, Leanne had driven off in her Mini, and that he had never seen again.

He stood by that account until trial, where it became blindingly obvious he had blood on his hands. Then, on the eve of his defence case - the point when he had the opportunity to tell the jury, his family, and their friends what had happened - he dramatically changed tack.

He pleaded guilty to manslaughter, but continued to deny murdering the mother of his children, whilst refusing to utter a word about what had gone on - leaving his lawyer to argue that jurors couldn't really be sure he'd meant to kill her, even though he had choked her for a least a minute, with such significant force two bones broke in her neck.

Detective Superintendent Aaron Duggan, who led the enquiry for Cheshire Police, said: “It’s a very tragic case. Leanne has been murdered by her husband.

"She has three beautiful children who now haven’t got a mother. The fact Darren has put then through this whole trial and kept them waiting for six months for this justice is ultimately the shame. We hope this conviction brings some comfort to his family.”