Joshua Davies, 16, was jailed for life on the 2nd September 2011 at Swansea Crown Court, for battering 15-year-old Rebecca Alyward to death with a rock and was told he would spend at least 14 years behind bars before being eligible for parole.
Davies was found guilty of luring Rebecca into woods near their homes. He tried to frame a friend over the killing and his barrister, Peter Rouch QC, told the court that he still insisted that he was not involved.
Mr Rouch said: "Although all murders are senseless, you can usually derive a reason or motive for the killing.
"In this case it is difficult to reason why it was that Rebecca came to be killed. All that we can say is that what happened in the forest that day had a terrible and ruinous effect."
The court was told that psychiatrists who had spoken to Davies found no condition that might explain his brutal attack. It heard that Davies had been a well-liked boy with no history of violence.
But the judge Mr Justice Lloyd Jones told Davies that he had a "deep-seated hatred towards Rebecca which eventually led you to kill her".
He said the teenagers had separated a year earlier with "bitterness" on both sides. He called Davies "devious, calculating and controlling".
Addressing Rebecca's family, the judge accepted that no sentence could make up for a lost life. Rebecca's killing was a huge shock in Maesteg, her home town, and the village of Aberkenfig, where the killing took place and where Davies lived.
The jury heard that Davies and Rebecca had known each other for some years and dated for three months.
After they parted, Davies began to talk about killing Rebecca, telling friends he would find a way of murdering her and getting away with it. He spoke of making a poison out of plants such as deadly nightshade.
Davies once asked his friends what they would give him if he carried out the killing. They say they did not take him seriously and promised to buy him breakfast if he did it.
On 23 October 2010 Davies and Rebecca arranged to meet in woods at Aberkenfig, a popular hangout for teenagers.
Rebecca wore an outfit she had bought the day before, possibly believing they were going to get back together. Before he left for the woods Davies smiled at one of his friends and told him: "The time has come."
After the attack, when a friend phoned him in the woods to ask him if he was with Rebecca, Davies coolly asked him to define what he meant by "with".
He later boasted to friends that he had attacked Rebecca, who was slightly built, from behind. She was screaming and the worst thing, he said, was seeing her skull give way. The rock he used to batter her was so heavy that in court during the trial an official struggled to pick it up with one hand.
Following the murder, Davies summoned a friend to the woods. The boy described in court how he "glimpsed" Rebecca's body lying face down, her arms splayed out. Davies was a "bit shaky" but "didn't seem upset at what he'd done".
The alarm was raised and a search was launched after Rebecca failed to return home.
Meanwhile, Davies updated his Facebook page to say he was "chilling" with friends. He had a cup of tea and watched Strictly Come Dancing and the film No Country for Old Men.
During the search for Rebecca he sent a text asking her to get in touch: "We're all worried," he wrote.
Rebecca's body was found in the woods the next day.