The two men had just finished prayers at the nearby mosque when they saw a horrifying sight - a young woman hanging from her fingertips from the ledge of a 20-floor tower block.

She couldn't hold on for long and plunged through the air and fell onto the concrete entrance at Norfolk Court in the Gorbals.

Horrified by what they had just witnessed, they called the police.

It was May 2002 and yet another tragic death in Glasgow.

The woman was 28-year-old drug user Joanna Colbeck.

Couple Rose Broadley, 38, and her partner Robert Butchart, 40, had taken pity on Joanna and given her a bed for the night.

Desperate for drugs, it looked as though Joanna had jumped out the window as they slept.

Broadley gave an interview to a reporter after the tragedy talking about how horrified she was at her friend's death.

But it seemed there was more to what had happened than what met the eye.

Joanna had told her mother she owed someone hundreds of pounds and was going to be killed if she didn't repay it. 

But despite her terror, she never revealed who the people were, except to say they lived at the flats where she would later die. 

Joanna's heroin habit had taken her from a respectable family home where her mum was an accountant to the red-light areas of Glasgow and Edinburgh. 

It emerged that Broadley, who had a string of previous convictions including assault to danger of life and robbery, sold heroin to Joanna and another street girl.

She would drive them from Glasgow to Edinburgh for sex work and took money from their earnings.  

A jury would later be told she had been violent towards Joanna and other girls who owed her money for drugs.

Broadley was said to treat Joanna 'like a slave' and had handed out vicious beatings with a baseball bat in the weeks before she died. 

Broadley quickly became a prime suspect.

However, there was one problem. No one had seen Joanna being pushed out the window.

Nevertheless, Broadley was charged with murder and stood trial at the High Court in Glasgow in 2004.

It was alleged that Joanna was regularly taken to the 20th floor flat at Norfolk Court in the Gorbals for beatings by her.  

One key witness, Joseph McCrimmon, described a number of occasions in which he had seen Joanna being attacked.

He recalled one particular incident when Broadley repeatedly punched and kicked her in the flat. Joanna had been taken into the kitchen and he could hear screaming and shouting.

One time he saw Joanna sitting on the floor, crying, with a cut to her face with Broadley calling her “a cow”. 

There was another occasion when he described Broadley as “going absolutely mental”, grabbing Joanna by the hair and shouting: "I'm going to kill you."

She had also shouted about stabbing Joanna and dragged her into a bedroom.

McCrimmon's partner, who also gave evidence, recalled Broadley punching Joanna and hitting her with a stick. 

She described an incident in which Joanna had said that she was going throw herself out of the window, to which the Broadley said: "Are you going to throw yourself oot the windae? Well, I'll help you!”

Before her death Joanna was living with Norman Morton in Sandyfield Place. 

He said that Joanna was terrified of Broadley and in debt to her.

Mr Morton was in the habit of going to meet Joanna on his bicycle at a video shop in the Saltmarket. To avoid bumping into Broadley they would take an alternative route home. 

One day as they were walking home, Broadley saw Joanna and confronted her in a tenement close after a chase and began threatening her.

It was at this point - the day before her death - that she was forced back to the flat in Norfolk Court by Broadley and Butchart.

CCTV showed Broadley frogmarching Joanna into a lift and whacking her across the face as it went up. 

A 14-year-old girl witness claimed Broadley told Joanna: "Wait till you get upstairs. I have got a surprise for you. Your name's written on it."

Another witness had overheard Joanna tell Broadley: “No Rose. Don't. My mammy's got money to pay you.”

It was in the afternoon of the following day, May 25, 2002, that Tasdaq Shah and Ahsan Ulhaque were in the car park of the mosque not far from Norfolk Court.

They spotted Joanna hanging from the window ledge with both hands and saw her letting herself go backwards and fall to the ground. 

They saw no-one else at the window and they heard no scream. 

The CCTV footage showed Joanna hitting the ground just after 2pm.

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Inspector James Steele told the jury that he later spoke to Broadley who seemed perfectly normal and said she hadn't heard or seen anything. 

The following Sunday morning Broadley and Butchart arrived at Mr Morton's house.

She told him that Joanna had jumped out of the window and was dead. 

They stayed with Mr Morton for the next few days while the police carried out their investigations at their own home.

However, during their stay an argument developed and Broadley allegedly told him: "Don't you start me, otherwise you'll be the next to go out the window."

It was also claimed during the trial that terrified Joanna was ordered onto a window ledge by Broadley and told: "See how long you can dangle."  

In his summing up at the end of the trial, prosecutor Geoffrey Mitchell urged the jury to find Broadley guilty of murder.

He added: "Joanna worked for Broadley and was terrified of her. 

"She wanted to get away from the vicious circle of heroin and was trying to avoid Broadley and dodging her. 

"She was treated worse than a dog and I suggest she was ordered to go out of the window as a punishment."

Mr Mitchell said one of the most important pieces of evidence was from Mr Morton who had been a friend to Joanna and who had been told by Broadley that he could be next out of the window.

Fingerprint evidence showed Joanna's prints on the window frame and sill. 

However, crucially, no fingerprints of Broadley were found.

She was in bed when Joanna went out of the window and had been later told by her son what had happened.

One thing was certain - Broadley had been in the flat when witnesses saw Joanna clinging by her fingertips from the window ledge before falling to her death.  

Her defence team had argued that Joanna had committed suicide while Broadley was asleep and there was no proof that she had been involved in Joanna's death.

However, despite the lack of fingerprint evidence a jury found the woman guilty by a majority verdict. 

Trial judge Lord Bracadale told Broadley she had been convicted of a “calculated and thoroughly wicked murder”.

In jailing her for life, Lord Bracadale said of Joanna: "It is plain she was in constant fear of you, and anyone who saw the CCTV film saw the fear in her face." 

Broadley was also found guilty of several assaults on Joanna before her murder in May 2002 at Norfolk Court, Gorbals. Butchart admitted an abduction charge.

In sentencing her to life, Lord Bracadale ordered Broadley to serve 15 years before being allowed to apply for parole.

However, in a dramatic development, the murder part of her conviction was overturned the following year following an appeal hearing in Edinburgh.

Broadley’s legal team said there was no evidence that Joanna had in fact been murdered as no one had seen her being pushed.

They argued that Joanna had committed suicide while Broadley was asleep in bed at the time.

Three judges at the appeal court in Edinburgh agreed and quashed the conviction.

However, Broadley remained behind bars as she was also serving a sentence for the attacks on Joanna.