ON Friday - day 42 of what had become the longest ever single-accused murder trial in Scottish history - the jury foreman rose to his feet in Edinburgh's high court and pierced the silence with a word that Jodi Jones's mother had waited more than 18 months to hear: Guilty.

The audible gasps and sobs that followed the verdict in court number three, however, contrasted starkly with the stony silence from 16-year-old Luke Mitchell. Handcuffed and flanked by two officers in the dock, the teenager did not collapse, shout or wail that a miscarriage of justice had taken place.

There was no visible anger when the verdict came. Instead, he faced straight ahead, and showed no emotion, just as he had done throughout the murder trial.

It was a calmness and stoicism that had become the trademark of the teenage killer, who, aged just 14, had in the most gruesome and calculated way strangled, stabbed, stripped and mutilated his girlfriend in woods near her home.

The words of the judge, Lord Nimmo Smith, were telling. He had sat patiently and intently throughout two months of the most harrowing evidence, and yet did not have an answer to the seemingly simple question: Why?

"It lies beyond any skill of mine to look into the black depths of your mind. I can only look at what you have done, " he told Mitchell. "I have no idea what led you to do what you did. Maybe it was a desire for notoriety, to achieve something grotesque.

I leave it to others to fathom."

Looking back at the judge and dressed in an open-necked blue shirt, black trousers and shoes, the ponytailed teenager again offered no clue as to his motive; just silence.

In his head, however, Mitchell must have replayed the moment he murdered Jodi on June 30, 2003, near the Roan's Dyke path that ran between their homes in Dalkeith, Midlothian. He would have recalled the detail of how, at around 5pm, he had met his girlfriend there and taken her over the wall into nearby woods.

It was here, according to forensic experts, that Mitchell punched Jodi several times on the face and then began to throttle her with his hands. At a time when she was likely to have been slipping in and out of consciousness he forced her to her knees and began a frenzied attack on her with his knife.

Jodi would have died instantly from a gaping wound that severed her major artery, but her neck had been slashed up to 20 times. Shielded only from the path by a wall, Mitchell then stood over his victim, stripped her of her trousers and scattered her clothes and spectacles around her.

Using her trousers to tie her hands behind her back, he continued the attack with ritualistic precision, mutilating his dead girlfriend's naked body by plunging his knife into her mouth, breast and abdomen. He slit her eyelids, being careful not to damage her eyes, and slashed her right arm twice.

When the pictures of the dead girl's body were shown in court, the judge described them as the worst he had ever seen. Nimmo Smith added: "What you did was to subject Jodi to a horrible death - and one can only hope mercifully quick. There must, however, have been a time before she became unconscious when she knew that you, her boyfriend, whom she held in affection and trust, whom she went out joyfully to meet, had turned into a fiend.

"You have been convicted of a truly evil murder, one of the most appalling crimes that any of us can remember, and you would rightly be regarded as wicked."

The brutal crime of a child killing another child has captured the public's imagination.

All are at a loss to understand how a schoolboy, still a year from sitting his standard grade exams, could become a cold-blooded killer.

It is still unclear, despite the biggest investigation mounted by Lothian and Borders Police in 20 years, whether the murder was planned or the result of an argument that began on that sultry June evening, perhaps about the girl, Kimberley Thomson, that Mitchell was seeing behind Jodi's back.

It was reported that the police chief in charge of the investigation had speculated that Mitchell killed Jodi after a row. Detective Chief Superintendent Craig Dobbie said:

"There is a potential Jodi found out about Luke's planned holiday with Kimberley that Monday. I think he told her at lunchtime.

"And if she found out about Kimberley, she would have challenged him."

Of course there are other theories. Did it happen because she had refused to have sex with him? Was it the product of Mitchell's interest in goth subculture, in satanism or his chronic cannabis use that led him to kill?

Was the killing rooted in the upheaval of his early years, the break-up of his parents when he was 10 years old? Or had he really been acting out some sick fantasy, as the prosecution suggested, of using his girlfriend to replicate the murder of Elizabeth Short, a Hollywood starlet, who had been killed in the 1940s in a similar way? The answers, more than 18 months on, are still curiously absent.

Certainly, nothing in Mitchell's early years gives any clue to the evil that would involve him as an adolescent. Two years before he murdered, aged 12, he is pictured at school in his uniform, his hair short and fair. A year later, another picture in the family album shows him uniformed, as a disciplined army cadet.

However, it is at the age of 14 that those who knew him say he began to change from the neat and tidy schoolboy. Although many parents may recognise their own children in the description of Mitchell, a boy who became dismissive of authority, who grew his hair, who began to wear baggy black clothes and have body piercings, this 14-year-old's actions were entirely different from normal teenage rebellion.

He began smoking cannabis in dangerous quantities, he obsessed over knives and immersed himself in the world of satanism, scrawling macabre messages and the so-called devil's number "666" on school jotters. In class, he wrote essays praising satanism and scratched 666 into his forearm. He kept bottles of urine in his room.

In court, a 14-year-old witness, Keith Campbell, said that Mitchell carried a knife "everywhere", even at school. It was also heard that Mitchell and a small group of friends, including Jodi, would go to an area of Dalkeith called the China Gardens, during school lunch breaks "pretty much every day" to smoke cannabis. After the murder, a knife pouch with the initials "JJ" and the number 666 written on it was found in Mitchell's bedroom. The brown leather pouch, which could be worn on a belt, was also scratched with the dates 1989-2003, apparently signifying the birth and death of his girlfriend.

Professor Vincent Egan, a chartered forensic and clinical psychologist, of Glasgow Caledonian University, who has followed the Jones murder, says it is possible to point to several factors that could have led to Mitchell becoming a killer.

"Murders of this kind are unusual but we see similarities in the background of Mitchell and in the backgrounds of other delinquent kids going off the rails. With drugs, there's no casual experimentation, he's using drugs in really a chronic way; he's carrying weapons, and that's not unusual in people who murder.

"Of course, most people with that profile don't commit murder, but there is no doubt that Mitchell was a troubled kid. There was a ritualistic aspect to this killing."

Mitchell, born on July 24, 1988, was the younger of two sons. His brother Shane - who was to be a significant figure in the case - had been born eight years earlier in 1980, the year his parents were married at Corstorphine Old Church in Edinburgh. In the semi-detached home in Newbattle, Dalkeith, life seemed relatively normal: his father Philip was an electrician and his mother Corinne ran a caravan park. Teachers in the local primary school knew Luke as a bright and attentive pupil.

It was in his later years, as an adolescent, that his demeanour and his interests changed. At the Catholic St David's High School in Dalkeith, his teachers became so concerned about his behaviour that they say they advised psychiatric help. According to evidence given at the trial, the bright and popular pupil had become something of a loner who disrupted class and argued openly with his teachers. In an essay, titled Pain And Suffering, he wrote: "If God forgives everyone, then why the need to be sent to hell? If you ask me, God is just a futile excuse, at the most, for a bunch of fools to go around annoying others who want nothing to do with them.

"Are these people insane? Open your eyes.

People like you need satanic people like me to keep the balance. Once you shake hands with the Devil then you have truly experienced life."

After this, his English teacher Geraldine Mackie referred him to the school guidance teacher.

Ian Stephen, another forensic psychologist, who was a consultant to the TV programme Cracker, says: "Children who kill like this are few and far between but they tend to be reasonably intelligent children. Mitchell, by all accounts, was considered an intelligent boy. People like that are usually loners who are isolated or different from their peer groups. Often there are unusual circumstances in their family life. There is very clear evidence for all of this in this case."

He adds that in other rare instances where children have killed other youngsters - Mary Bell, and Jamie Bulger's murderers, Jon Venables and Robert Thompson - they have been considered to have been bright.

In the case of Bell, who was found guilty in 1968 of killing two young boys in Newcastle, she went out to help in the search for her victims after they had been reported missing.

It was this same act that led to Mitchell's downfall. His crucial mistake was to join the search for Jodi and then to "find" her at a place that nobody else had thought to look.

Stephen says: "When Mary Bell killed, she helped to look for the babies. To some extent it's about making yourself visible. There is an element of maintaining contact with the crime.

It's like making a hoax call to the fire brigade and staying to watch the fire engines turn up.

"In the Mitchell case, the murder may not have been a game but it may be that this has been done to act out his fantasies. Kids, and adolescents especially, have fantasies of killing. Most don't act on them but you find very often that serial killers will have had fantasies of killing which started in childhood."

With unbelievable speed of thought and coolness, 14-year-old Mitchell set about putting his cover-up plan in place almost immediately after he murdered Jodi. At 5.40pm he calmly phoned Jodi's house and spoke to Mrs Jones's partner, Allen Ovens. He asked for Jodi and was told that she had already left to meet him. Nobody in the house realised that it was, by then, some 50 minutes since Jodi had left, and no alarm bells sounded. Mitchell's alibi was that he has hung around, in and about his home, waiting for Jodi and eventually went off with some friends when she did not turn up. The group went to nearby woods to smoke cannabis. At no point was there a hint that Mitchell was agitated or distressed.

At 10.40, some 40 minutes after Jodi should have been home, the alarm bells began to ring.

Her mother sent a text message, intended for Jodi, to Luke's mobile phone. Using her pet name for her daughter of "Toad", the text said:

"Two weeks grounding Toad, say bye to Luke."

Again, with a composure that belied his age, Mitchell phoned back to say he had not seen Jodi all night. Panic set in, and Mrs Jones began phoning friends and relatives, and reported Jodi missing to police. During the calls, Mitchell agreed to search the path from the Newbattle end, and meet up with Jodi's grandmother, Alice Walker, her sister Janine and Janine's fiance Steven Kelly. What happened next became the crucial aspect of the trial.

Using torches in the dark, Mitchell began to search for the missing girl with his German shepherd dog Mia. In his statement to police, he said: "We walked past the V-shaped break in the wall and a few yards past that, not even 20 yards past that, Mia stopped and put her nose in the air and put her paws up on the wall as if trying to sniff over." He then went across the wall alone and continued searching. The statement continued: "I saw this white thing stuck out in the light. I could see it was legs, like a tailor's dummy. After I saw legs I just took another step then I recognised it was a body lying there. I could see it was female. There was blood on the neck. She was naked."

But three witnesses at the trial said there was no way Mitchell that night had gone anything like the distance beyond the V and then come back. He had headed straight to the V, gone over and immediately turned to his left rather than to the right or walked straight ahead. It was the fact that Mitchell appeared to know where to find the body and to see it from such a long way in the dark that led the jury to believe that only if he had known she was there in the first place would he have found her body.

Even as the verdict was announced, Mitchell never abandoned his cool demeanour. Despite being the subject of intense police and media scrutiny for more than 18 months, and especially in the first months after the murder, he did not crack.

As Luke was merely 14 years old, speculation is forming around Corinne Mitchell that she may have played more of a part in the murder than just the role of a mother. Police believe the 45-year-old's relationship with her son changed from parent to that of accomplice. Mrs Mitchell had claimed Luke had been cooking dinner at the time of the murder, even though her older son Shane said he thought the house was empty.

Some have said that the relationship between Luke and Corinne Mitchell went beyond the "normal" mother-son bond. The relationship was said to be extraordinarily physically close.

When police arrived to arrest the teenager they found him sharing a bedroom with his mother.

She explained she was comforting him because he had not been sleeping well.

At Jodi's graveside, she made a show of embracing her son for more than five minutes.

Earlier that day, when the teenager protested his innocence on television, she constantly stroked his neck to comfort him.

A former babysitter for the family has said:

"Corinne was really weird with the boys. She liked to dress them just like herself when they were young. If she wore leg warmers, they were put in leg warmers."

Others close to the family describe Corinne as a well-spoken women, fiercely protective of her sons. She was someone who appeared to "have a hold" over Luke. Under her protective gaze, Luke was to give an extraordinary television interview protesting his innocence on the very day Jodi was buried. The Jones family had told him bluntly that he would not be welcome to attend. In the interview, given to Sky News, mother and son had penned a poem in Jodi's memory, and Mitchell read it to the cameras.

With her son now awaiting sentence it is unclear whether Corinne will face new charges.

One of the most contentious issues raised in the trial was Mitchell's interest in so-called goth culture. His black baggy clothes and his interest in the singer Marilyn Manson came in for special scrutiny as it was suggested that the US singer may have influenced the killing.

At court, Detective Constable Adam Brunton said the postmortem photographs of Jodi were similar to images downloaded from the musician's official website. One of the images in particular was of interest to the police: a depiction of the unsolved murder of the actress Elizabeth Short in 1947, later labelled the Black Dahlia case. The US singer had professed an obsession with the case.

At the height of the Jodi Jones case, the jury were shown a series of paintings by Manson of the Short murder, which it was claimed bore a striking similarity to Jodi's killing.

The link between Manson and Jodi's killing have been dismissed as "nonsense". Dr Paul Hodkinson, author of Goth: Identity, Style And Subculture, and a lecturer in sociology at Surrey University, says: "The police actually used the various bits of popular culture as evidence. The number 666 written on pencil cases and jotters is a very common thing among teenagers, not just those who are involved with goth culture.

"There are a huge amount of people in society, not just young people, who enjoy elements of popular culture that involve angst, death, violence and sex . . . Instead of blaming Marilyn Manson for the death we should be investigating what is the difference between Luke Mitchell and the other 99.9-per cent of people who like Manson and who do not go on to kill. That would be an enormous investigation but we should be looking at his personality and his life rather than the singers he happened to like."

Jim Poyner, a photographer and formerly of NuArts, a community project involving Glasgow's goth culture, says: "These people are normally introverted. They are more likely to be discriminated against than to cause violence.

"The worrying thing is that this verdict will impact most heavily on goths when the fact is that the kid who murdered Jodi Jones could have been wearing anything. There has been more violence committed in the name of football than will ever be committed in the name of music."

In Glasgow, goths too dismissed the link.

Joseph Lochran, 17, dressed in the traditional goth look - sweatshirt, baggy jeans, and piercings - says: "If you like a certain kind of music you will be labelled a goth, but comparing him to us is f***ing ridiculous. If you are going to kill someone then you'll kill them, won't you? It wouldn't matter what kind of music you liked."

But there is no doubt that the trial provided an insight into today's teenagers and their culture. Jodi Jones herself was a goth, intelligent, shy, and yet she was heavily into cannabis and had self-harmed. Her diaries showed that she had considered death revealing her affection for Luke. She wrote: "God, I think I would die if he finished with me. When I am not with him, I want to be. He is the only person who makes me forget about most of the shit in my life.

"No matter what he says, I believe him and that is really dangerous. I will have to be very careful. I have had my trust broken too many times."

It also emerged that Jodi had started smoking cannabis before her relationship with Mitchell. While they were together, he was a regular supplier for her. Jodi's mother, Judy, had said she was "really, really shocked" at discovering her daughter's drug use. "I smoke and Jodi would not even pass the ashtray or touch my cigarettes."

Later, after the verdict was announced, Judy Jones released a statement. It read: "[ Jodi] had come to a point in her life of getting through her low self-esteem and was happy in having her first boyfriend. On this I will say no more, but that there can never be warnings of this type of evil.

"On the use of cannabis, there is no detriment to the clever and wise person she was. Many teenagers, wise and clever, go through these phases."

Julie Bertagna, the author who writes for adolescents, says the case may have opened up the eyes of parents to today's teenage culture. "It's such a short period of your life and everything seems more extreme, you are trying to find out who you are and it can be such a confusing time.

"Experimentation has always been a part of teenage culture. There seems to be more access to drugs and alcohol and with the internet you can get to see a lot more than you could in the past. The interests of teenagers may seem strange but perhaps you forget as you get older what it's like to be a teenager."

In Easthouses, where Jodi's body was found just over 18 months ago, long shadows loomed over the area despite the guilty verdict and the appearance of a piercing midwinter sun.

It is a village still numb from the shock of a crime of such violence that it would bring any small community to its knees. That the perpetrator of what the judge called a "truly evil murder" has left an understandable but ugly sense of bitterness in the area. There is little sympathy here for the killer that Donald Findlay QC, his defence lawyer, described as "just a 14-year-old boy".

"He should be killed in jail if you ask me, " says Kenneth Quinn, 17, one of very few people who agrees to be identified. "He definitely deserves everything he gets." Quinn says far more besides, none of which is printable.

A woman on the street outside Jodi's mother's house, which sits in a neat little estate just a few hundred yards from the wooded spot where Jodi was stabbed to death, echoes Quinn's sentiments, if in a slightly more restrained manner. "I'm glad they've nailed him. He deserves everything that happens to him. I'm just really glad it's over and they've sorted him. You do eventually move on, but you never forget. You learn to live with it. There's nothing else we can do. I'm just glad it's done. I'm glad they've got him."

She says that there had never been much sympathy for Mitchell on this side of Roan's Dyke, the shaded path running from Easthouses to Newbattle which the two young lovers used to frequent.

"To me, from day one, I really thought it was him. I walk past here every day. To see it every day . . . for the family's sake, I'm glad it's over" Her reaction was typical of the feeling in this former mining village, some 10 miles south of Edinburgh. Although once close-knit, the community here has been unravelling since the mines started closing: the Lady Victoria Colliery in nearby Newtongrange, once the showpiece of the Scottish coalfields and now a mining museum; Easthouses, which closed at least 20 years ago; and Bilston Glen, one of deepest mines in Europe, which was shut in 1989 after flooding during the miners' strike. This is a traditional mining area without a mine.

The bitter irony is that the murder seems to have brought the community closer together again. Residents have responded to every call by the police for information, they have shared every rumour and followed every twist of the court case. Now they seem united in their disgust, yet unable to escape the tragedy that has hit their community.

Paul Neilson, of Newtongrange, emerges from the Balmoral Motor Company, immediately adjacent to a temporary roadside shrine to Jodi, where flowers and a teddy bear are still taped to a lamppost. He says he felt that only one man had ever been guilty, and that man was Luke Mitchell.

"My personal reaction and the reaction of my mother and father is he deserves what he gets. The people in the streets and pubs all feel the same way."

For months after Jodi's death, this garage was plastered with police posters calling on the public to come forward with any information on the murder. It has since changed hands.

At the other end of the village, past the two carry-out shops, roofing business and a property agent which make up Easthouses's only retail outlets, sits the local corner shop. It too has changed hands since the murder. The changes in ownership may not be connected to the murder, but it would be far from surprising if some people felt the need to move away from Easthouses after what has happened here.

In particular, the revelations of drug taking among school pupils have shocked onlookers.

The only acknowledgement here is that Mitchell "must have led them on", as one man puts it.

However, Professor Neil McKeganey, founding director of the Centre for Drug Misuse Research at Glasgow University, says studies have shown that outlying communities similar to Dalkeith and the former mining villages of Easthouses and Mayfield were open to a "ready flow" of drugs from the urban centres.

"That has been noted in a number of ex-mining villages, " says McKeganey. "The impression that drug use, exchange and sharing is something that occurs only in cities is certainly not the case."

McKeganey says the level of cannabis use attributed in court to Luke Mitchell - up to 300 joints a week - seemed "frankly impossible".

But he adds: "The young man seemed to have an exceptionally high level of cannabis consumption, and cannabis has been associated with psychotic episodes."

Inside the Miners' Welfare Club, the nearest thing to a focal point that the village possesses, men sit or stand around with pints or halves as they watch a televised press conference of the police reaction to the trial verdict.

"Ijust feel it's the right verdict for the family, it helps them, " says one local, who only gives his name as Tam. "The village has gone through a lot with what's happened. The whole community got right behind the family when the thing first happened. It's one of those communities where they tighten up and keep things to themselves. Being a mining community, that's the sort of thing that always happened. They just gathered together and stuck together."

On the television, Detective Superintendent Craig Dobbie, the officer who lead the investigation, cannot shield his emotions as he says the guilty verdict might provide "some answers" to the anguish Jodi's family had suffered during the past 18 months. He previously described the murder as "monstrous" and one of the worst he had witnessed in almost 30 years in the job.

Nowhere here is there much doubt that Mitchell is the murderer. The impression given is that everyone has presumed his guilt from the very beginning, even if most were reluctant to say it publicly before.

Even so, Tam was not alone in feeling a sense of relief at the verdict. Many in Easthouses thought the jury might not be as convinced of Mitchell's guilt as they were. "We all say in the village that he's guilty, " Tam says, cradling a half. He pinches his thumb and forefinger together. "And he was that close to getting off.

"It has been proved there have been lies told. Thankfully the jury have seen through it.

I take my hat off to the jury, what they have had to go through and what they have had to see. There's a sigh of relief now."

He adds that the Mitchell family would most probably have to move away from the area.

By now, Sky News has started re-running the interview Mitchell gave on the day of Jodi's funeral, an interview that criminal psychologists pored over for clues to the slaying. Everyone pauses, drinks held in mid-air, as the tape from the summer of 2003 shows Mitchell protesting his innocence.

"Aye, right son, " says one man. "Lying bastard."

Down the road in a small park that overlooks Jodi's family house and onward to the snow-dotted Pentland hills beyond, an elderly man limps along with his spaniel in tow. Even here, so close to the murder, there is no hint of an answer as to what drove a 14-year-old boy to murder Jodi.

"Hopefully they've got the right man, and hopefully the mother can move on now, " the man says. "But people here will not forget this."