The sister of a teenage girl who was murdered and set on fire was terrified she would be the killer's next victim after he showed her the body, a new TV documentary has revealed.
Robert Bayne beat 17-year-old Zoe Nelson to death before burning her body in woodland near her home in Wishaw, Lanarkshire, in May 2010.
The bodybuilder, who was then aged 20, had been going out with Zoe but he was also seeing her younger sister Laura Anne, then aged 16.
Bayne showed Laura Anne her sister's charred remains but she kept quiet for five days before telling police after he threatened to kill her.
The horrific case is featured in a new episode of Crime+Investigation documentary series Murdertown, presented by Anita Rani.
Retired Police Scotland Assistant Chief Constable Derek Robertson, who led the murder investigation, told the programme Laura Anne was frightened of revealing the truth at first because of Bayne's fearsome reputation.
He said: "Laura Anne was interviewed by specialist family liaison investigators, we thought she could help us because she knew her sister and what was going on in that community.
"But we just weren't getting that information. It was as if she shut down inside, she just withdrew into herself.
"I remember speaking to her mum and her aunt about it and they said 'That's just who she is, she's very shy'.
"We knew there was more to give, we always knew that, but the reasons why we didn't have a clue on to be honest."
The former detective praised Laura Anne for having the courage to speak out and help them catch Bayne.
He added: "We had witnesses who had seen Robert Bayne with Zoe but we did not have him at the scene, we did not have him actually doing the murder.
"Laura Anne was a very introverted character, shy and nervous, and we worked very hard with her to get information.
"On the Friday afternoon late on that was when she said 'I know he killed Zoe. I know he killed Zoe because he said to me he killed Zoe'.
"She basically said she had been seeing him and her sister had been seeing him and they fell out.
"The day after she went to return clothing to Bayne and he took her to the murder scene and pointed Zoe out. She recognised her from a tattoo and Bayne told her 'If you say anything that will be you'.
"Robert Bayne towers over her, massive muscles, dominating, controlling, threatening. You can imagine the fear in the girl.
"That shut Laura Anne down and made Robert Bayne feel even more confident as the week went on that she hadn't spoken."
Bayne's trial heard a member of the public found Zoe's badly burned body the day after the murder but believed it was a charred tailor's dummy before realising it was a corpse.
He disposed of Zoe's mobile phone and later told officers another person had admitted to killing the student. When the unanimous guilty verdict was read out, Bayne went berserk, shouting vile abuse at his victim's family and headbutting a security guard.
Bayne claimed the length of sentence was "excessive" and launched an appeal but two judges rejected the move in January 2012.
Lord Reed agreed the sentence was at the "upper end of the scale" but ruled it was appropriate due to the gravity of the case.
The episode of Murdertown on Zoe's killing will be shown on the Crime+Investigation channel on Monday at 9pm.
Don't miss the latest news from around Scotland and beyond - Sign up to our daily newsletter here .
