The real killer of a 15-year-old schoolgirl escaped justice for 40 years while another man went to jail, a court has heard.
Stephen Hough, 58, allegedly choked Janet Commins to death as he brutally raped her but was only arrested 40 years later after a billion-to-one match of his DNA from samples taken at the time of the 1976 murder in Flint, North Wales.
In the meantime, another man, Noel Jones, pleaded guilty to manslaughter and was jailed for 12 years, Mold Crown Court heard.
But while Jones did not challenge his conviction, he maintains he is innocent and "only confessed due to pressure placed upon him at the time", Mark Heywood QC, told the jury as he outlined the prosecution case against Hough at the start of his trial.
"The prosecution case is that, when you consider all the evidence in this case, there is support for Jones' claim that he was not Janet's killer and, in all the circumstances, you can be sure that Stephen Hough was," Mr Heywood said.
Janet, an only child, disappeared on January 7 1976, after leaving a note for her parents, Eileen and Edward, saying she would return to their home in Flint at around 8.30pm that evening.
Four days later her body was found by children playing hide and seek, in a thicket near Gwynedd School in Flint.
Injuries and tears to her body showed she had been forcefully raped while being choked, Mr Heywood told the jury of seven men and five women.
Semen and cell samples were taken from her body, preserved and stored on the police database.
As part of the large-scale murder inquiry, all local young men up to the age of 22 were visited by police and asked to account for their movements on the night Janet disappeared.
Hough, aged 16 at the time of the murder, a keen rugby and ice-hockey player and "very fit young man", told police he had been stealing petrol that night. He was charged with theft and fined, and went on to join the Army at the age of 21.
Police also interviewed Jones, then aged 18, who was eventually charged with murder before pleading guilty to manslaughter and serving six years in jail. While his conviction still stands, he asserts he is not the killer, the court heard.
In the 40 years since the murder, forensic science has "developed considerably beyond their past limitations", the prosecutor said.
In 2016 police took a sample of Hough's DNA in circumstances "that are of no significance to this case", Mr Heywood said - but it matched the sample taken from the victim in 1976.
The jury heard that the DNA profile taken from sperm cells at the crime scene matched Hough's profile, and it was calculated to be a billion times more likely to have originated from him than anyone else.
On September 4 last year he was arrested on suspicion of murder.
He maintained that the night Janet went missing was the night he was caught stealing petrol and denied knowing her.
The defendant made "no comment" when detectives put the DNA evidence to him, the jury was told.
Hough, of Flint, denies murder, rape and buggery, between January 5 and January 12 1976.
The trial, scheduled to last up to three weeks, continues.
A statement from Eileen Commins, Janet's mother, said she had told her daughter she could not go to the swimming baths with friends on the night she disappeared as she did not look well enough.
Janet had gone into a bit of a sulk in her room and then later "sneaked out", her parents finding her open pencil case and a note in her bedroom saying she would be back by 8.30pm.
They were not "unduly worried" at first, but as time went on Mrs Commins, a nurse, and her steelworker husband later called on her friends, began a search and then eventually called police.
Janet was last seen wearing flared trousers, a blouse, navy blue coat, wedge shoes and knee-length socks.
Cheryl Macklin used to walk home from school with Janet each day. In a statement, she said Janet was keen on hockey and music and "rubbish" at science.
She added: "The death of Janet had a dramatic effect on me and the whole of Flint.
"I constantly felt Janet should be with me enjoying life.
"Janet was a nice girl with an outgoing personality.
"The whole community changed overnight. It was as though my freedom had been taken away from me.
"Children would not be allowed in the street to play as they once had prior to the death of Janet."
The trial was adjourned until Wednesday morning.