SHE called the police to remove her son from suspicion, but crucial evidence that followed from that telephone conversation led to him being charged with the rape and the brutal murder of six-year-old Alesha MacPhail.

Footage from the security cameras she had installed to safeguard her senile mother showed that the 16-year-old boy – who, like his 54-year-old mother, cannot be named for legal reasons – had left their home on Bute and returned three times during the night last July when Alesha died, on one occasion coming back without his dark hoodie.

That garment was found hours later on the shore by one of the searchers for the missing girl, collected by police, then thrown into a skip at the back of Rothesay police station, before it was realised it might be evidence, then retrieved.

The schoolboy, described by his friends as being good at maths, but with a dark sense of humour, is on trial at the High Court in Glasgow charged with abducting, raping and murdering Alesha. He denies the charges.

Statistically the island of Bute is one of the safest places in the country, at least since the US Navy departed and Glasgow holidaymakers swapped “going down the watter” for Spain and Portugal. So there was no reason to worry when the six-year-old left her mother Georgina Lochrane and home in Airdrie for a three-week holiday with her grandparents and her mother’s former partner, Alesha’s dad, Robert MacPhail. She had been there less than a week when she was found dead, naked and suffering from more than 100 injuries, in scrubland in the grounds of the former Kyles Hydro hotel, minutes from the house in Port Bannatyne.

The evidence the jurors have been hearing, and the crime scene photographs they have been shown, is extremely harrowing. The connection of the accused to Alesha, MacPhail and his new partner, 18-year-old Toni McLachlan, is that the couple sold the boy cannabis, as they admitted in court. Both, however, deny supplying him on the night the child was murdered.

On that night, Sunday July 1, the boy and around 15 of his friends had been partying in the family home, drinking and smoking cannabis. He had fallen out with his mother, a stool had been broken, and he went to bed shortly after 1am on July 2, the worse for wear.

It is the Crown's contention that he subsequently got up and left the house three times, captured on CCTV, abducted Alesha from the nearby grandparents’ house and subsequently raped and murdered her, by smothering and strangulation.

Two witness have described seeing seeing, on CCTV, someone in a dark hoodie holding what looked like a child, walking along the shore at around 2.30am. The forensic pathologist who carried out the post mortem on Alesha – who described the 117 injuries on her as the worst he had ever seen – confirmed that the soles of her feet were clean and agreeing the prosecution assertion that was likely she had been carried, barefoot, to the woods where she was later found.

Alesha had been put to bed that night by her father and Toni McLachlan. But shortly after 6am the grandparents discovered that she was missing and at 6.23am alerted police. Around 7am the search for her began.

A message was also posted on Facebook about the missing girl and calling for volunteers to help with the search. It was through this message, by the grandmother, that her mother Georgina, at home in Airdrie, first learned of the search.

She commented on the post, asking: “Someone tell me what’s happened that's my daughter.”

The noise made by the searchers looking for Alesha woke the mother of the 16-year-old accused, She checked her back garden, woke her son and asked if he had heard anything, she told the court. He answered “no” and went back to sleep. On another occasion he told her that he must have gone out trying to buy “weed”.

Footage from the CCTV cameras was played and she identified her son leaving home at 1.54am, wearing all black clothing and returning as 3.35am no longer wearing the hooded top. Nine minutes later the video shows a light being turned on in the bathroom and he is seen leaving a minute later, at 3.45am, wearing shorts and carrying a T-shirt. He returned at 3.52am wearing the top, but left six minutes later and is seen carrying a torch and jogging. He finally returns at 4.07am.

The mother described how she spoke to her son and asked him if he had been out. “He said, ‘Oh did I? I don’t know, I must have been looking for my phone’.” She said that his feet were dirty. She then told him about the missing girl and asked him if he knew anything about it. He said that he didn’t.

Asked by advocate depute Iain McSporran QC if she had spoken to him again before his arrest, she responded: “I talked to him and tried to explain that whoever had done this to this little girl, their DNA would be all over her.

“He was adamant, absolutely adamant, that he had nothing to do with it. He said there was no way they would find DNA on this little girl because he hadn’t been with her.”

The prosecutor asked her why she had called the police. She replied, “It was just to help the police. Maybe he had seen something that he would not tell me. It was to eliminate him from their inquiries basically.”

The 16-year-old has lodged a special defence, alleging the murder was committed by Toni McLachlan, the partner of Alesha’s father Robert. In her evidence McLachlan strongly denied it and said that the first time she had heard the allegation was on the first morning of the trial, last Monday. The accused boy claims that on the Sunday night of the murder he had sex with McLachlan in a woodshed, that he used a condom provided by her and that she had then “planted” the condom with his semen to implicate him. He also claims that he gave her a hoodie to wear because she was cold. McLachlan totally refutes his account.