Care worker Stephen Nicholson brutally murdered schoolgirl Lucy McHugh after their "secret sexual relationship turned sour" and he had to silence her.
The 25-year-old grew concerned Lucy, 13, was going to blow the whistle on their intimate secret, revealing him as a paedophile to her family who had taken him in and given him a home.
Prosecutor William Mousley QC told jurors last week the case against Nicholson was "compelling" and the only obvious verdict was that he was guilty of the vicious murder and of having sex with the child.
On Wednesday, the jury agreed, finding him guilty of her murder.
Nicholson was also found guilty of sexual activity with a child in relation to another girl in 2012, who was aged 14.
He was acquitted of a charge of sexual activity with a child on multiple occasions when Lucy was aged 13.
Nicholson, originally from Southampton, lured Lucy to her death in woodland at Southampton Sports Centre on July 25 last year.
When she arrived, prosecutors said he "brutally" stabbed her, leaving almost 30 knife wounds which included three "very dangerous" cuts to the carotid artery in her neck.
He then fled the scene, changing out of bloodstained clothes and dumping them in a small stream on the journey back to his home.
Despite admitting in court the clothing found in the stream, known as Tanners Brook, was his, he said he had "no idea" how it got there.
Describing Nicholson's evidence in his closing speech today at Winchester Crown Court, Hants, Mr Mousley said: "This is a case of lies and more lies in the face of an overwhelming case.
"There were times during Mr Nicholson's evidence that I was reminded of an old blues song called 'Born Under a Bad Sign'. It's a tale of someone who, through no fault of his own, was just always getting in trouble."
The prosecution said that Lucy became "scared and worried" after her relationship with Nicholson turned sour.
Key evidence in Facebook messages remains hidden
The investigation into Lucy's death, described by the CPS as "one of the largest in criminal history" was hampered when Nicholson refused to give police his Facebook password.
After applying through the US courts for access to his account, prosecutors only received a log of his Facebook contacts with Lucy but not the content of any messages. It finally arrived the day that the trial started.
The defendant, who admitted dealing cannabis, claimed he had not wanted to reveal his drug contacts via his Facebook account out of fear they would attack his family.
Nicholson, a tattoo artist, was convicted of targeting another girl aged 14 who he had sex with as a trade for giving her a cheaper tattoo.
The defendant denied having an appetite for sex with underage girls and said he did not have a relationship with Lucy.
He claimed Lucy had been "stalkerish" towards him and he had been at the home of an elderly friend when she was murdered.
Nicholson was linked to the murder through DNA evidence from both him and Lucy found on clothing, described by prosecutors as his "murder kit", which was discarded in woodland in Tanner's Brook, about a mile from the murder scene.
He also tried to cover his tracks by inflicting wounds on Lucy that could be interpreted as self-inflicted and also posed in different clothing on CCTV at a Tesco Express store.
The court heard that Nicholson, a father-of-one, had a love for reptiles and had a collection which included 12 pythons, chameleons, geckos and corn snakes.
Nicholson also told how he enjoyed "soft choking" women during sex which involved squeezing their neck to intensify the sexual effect.
After the verdict, Detective Inspector Lee Macarthur read a statement on behalf of Lucy's mother, Stacey White, outside court, saying: "I would like to thank from the bottom of my heart the support from our close family and friends during this harrowing time.
"The dedication from Hampshire Constabulary, the specialist teams across the country and the local communities helped to get justice for my precious daughter Lucy."
Difficult home life of Harry Potter lover Lucy
Lucy McHugh lived a chaotic last few months before she was murdered by the best friend of her stepfather.
The 13-year-old was described by her mother, Stacey White, as her "smiling lip gloss angel" who was loved for her "generosity and kindness".
But the trial at Winchester Crown Court heard the family home in Mansel Road East, Southampton, was plagued by arguments, primarily between Lucy and Stephen Nicholson and also between Lucy and her mother's partner Richard Elmes.
Nicholson had lived at the house as a lodger for about a year after being invited by Mr Elmes because he had fallen out with his mother.
The court heard Nicholson - who had been best friends with Mr Elmes since they were children - would keep pet reptiles in the house and he said he stored cannabis in a kitchen drawer to sell to friends and clients.
The extent of the arguments meant Lucy repeatedly decided to leave home and live with her grandparents, Dawn and Darren White, including for one period of six months until about May 2018.
Mr Elmes told the court there would be arguments "the majority of the time" in the house, saying many were between Lucy and Nicholson, which led to him asking the defendant to leave the house just a few days before the murder.
He described witnessing one argument between Lucy and the defendant as like walking in on a "war zone".
Nicholson told the court he had sworn at Lucy and pushed her violently, and he admitted his behaviour towards her had been "too much".
Lucy had written in her diary of having to barricade her bedroom door to stop Nicholson forcing his way in on one occasion.
Mr Elmes said in court that he argued with Lucy as well.
He admitted sending a message to the teenager's mother Ms White saying: "I'm going to end up punching Lucy."
Ms White replied: "If you punch a child you will end up in jail so is it worth it, seriously?"
Ms White sent another message saying: "She is going to end up in care, she is accusing all of us of hitting her and throwing her about."
Lucy was described by prosecutor William Mousley QC as "vulnerable" and was receiving care from Child and Adolescent Mental Health Services, which had diagnosed her with attention deficit hyperactivity disorder.
Detective Superintendent Paul Barton, of Hampshire Police, said Stephen Nicholson had exploited Lucy's family who had taken him in as a lodger when he had nowhere else to live and used their hospitality to target the 13-year-old for sex.
He told PA: "I would describe him as cold and calculated, I would describe him as a paedophile and I think he is someone who only thinks about himself and has taken full advantage of this family that have looked after him, provided a roof over his head.
"He has targeted Lucy, taken advantage of her and when she wanted a relationship with him, he has taken the decision to silence her once and for all by brutally killing her."
Mr Barton said he believes the murder of the 13 year old was premeditated as Nicholson had taken steps including ordering new trainers in advance, showing himself in different clothing on CCTV at a Tesco Express and by luring Lucy to the sports centre despite not being on talking terms with her.
He said: "There are a lot of signs which would suggest that Nicholson had been planning this, maybe only for just a few days.
"All these things indicate to me that he knew exactly what he was doing, which makes this even more vicious."
Mr Barton said Nicholson might have attempted to cover his tracks by inflicting wounds on Lucy that could have been interpreted as having been self-inflicted.
He said: "He probably knew that Lucy was vulnerable and there is the suggestion that vulnerable children try to self-harm to get attention, so he may well have been doing that."
Mr Barton said Nicholson could have been using his second job as a tattoo artist to target underage girls.
The defendant was also convicted of sexual activity with a 14-year-old girl in 2012 who had contacted him to have a tattoo, and another girl described how he groped her upper thigh while giving her a tattoo.
Mr Barton said: "This investigation has uncovered that he has an unhealthy interest in young girls aged under 16. We heard of his tattoo business where he has tattooed young children and it has been established he has had sexual relations with Lucy and another girl who was underage.
"He's a predatory paedophile who took those opportunities when he identified vulnerabilities with young girls and took that to the next level by sexually abusing them."
"She had told a number of people she was pregnant with his child"
John Montague, senior prosecutor for the CPS in Wessex, said Nicholson killed Lucy to prevent her telling people they had a sexual relationship and claims she made that she was pregnant with his child.
He said: "The motive is that she was in a relationship with him and had been for a significant period of time and he had to shut her up in one way, and that's the only way he thought he could do that and he stabbed her round the throat.
"The post-mortem indication was she wasn't pregnant, I do not know what she was thinking at that particular time, perhaps she had missed her period, she had told a number of people she was pregnant at that time with his child.
"She was a child abused by Nicholson for a significant period of time. In my mind the sexual element is clear from the evidence I reviewed."
He added the evidence collected against Nicholson was gained from "one of the biggest searches in criminal history".
Mr Barton said the "major breakthrough" came when Nicholson's phone was identified as having entered an area of woodland called Tanner's Brook on his way home on the day of Lucy's death.
On the first day of searching the area, police found clothing that has been described as the defendant's "murder kit", comprising of a blue hoodie and other clothing which had DNA links to both Nicholson and Lucy.
Mr Barton said: "Our case at that point was a strong circumstantial case but by having the DNA evidence, that was the final nail in the coffin for Nicholson.
"This is one of the largest murder inquiries that Hampshire Police have seen over the years, we had hundreds of people working on this for many months, putting together a really comprehensive case which fortunately has seen Nicholson found guilty now.
"At any one time about 200 officers at the height of the investigation, we had a large search team that was using additional resources from other police forces, we had additional investigators being brought in from other police forces, so it really was a huge investigation at a time when resourcing was a challenge for us over the last summer period.
"CCTV was a massive line of inquiry for us, we had over 15,000 hours of footage that we needed to go through to try to identify Lucy, also Nicholson and any other witnesses."
Mr Elmes told the court she had self-harmed and the kitchen door was kept locked to keep her away from knives.
The lack of stability in Lucy's life was also shown by her changing secondary school after just one year.
Southampton City Council's social services were alerted by her schools after Lucy told friends that Nicholson was her boyfriend.
She also told friends he had got her pregnant and she had an abortion.
Ms White released a tribute to her daughter on what would have been her 14th birthday in October last year.
She said Lucy was killed as she was just beginning the "adventure" of her life.
Ms White described her as "a mixture of fun, laughter, generosity, kindness and whose biggest critic was herself".
She continued: "A smiling, content little dolly who everyone adored and cherished.
"You soared through your life doing so many things, you never let anything stand in your way.
"You loved so many activities: sports, art, drama, music, travelling, beaches and so much more."
She added that Lucy had a love of Harry Potter and trips to theme parks and to Cornwall.
"Cold and calculated predatory paedophile"
Stephen Nicholson was a "cold and calculated predatory paedophile" who preyed on vulnerable girls to satisfy his sexual appetite, according to the detective in charge of bringing him to justice.