A murderer has made legal history by becoming the first person to be brought to justice after changes to the double jeopardy law.
Billy Dunlop had been acquitted of the 1989 murder of his former girlfriend Julie Hogg, of Billingham, Teesside.
He later confessed his guilt to a prison officer, while serving time for assault, knowing that he could not be retried for the same crime.
But the law was changed in 2005 and Dunlop, 43, pleaded guilty on Monday.
Under the previous 800-year-old law, anyone acquitted by a jury could not be retried for the same offence.
Dunlop could only be prosecuted for lying at his trial. He was given six years in jail for perjury.
After the law was changed in April 2005 Cleveland Police re-opened the case.
Miss Hogg, a pizza delivery girl, was initially reported missing.
Her body was discovered months later by her mother, behind a bath panel.
Dunlop, a labourer who lived nearby and had had a brief relationship with her, was charged with the murder.
He faced two trials, but each time the jury failed to reach a verdict and he was formally acquitted in 1991.
The victim's mother, Ann Ming, campaigned tirelessly for a change in the law and described Dunlop as "pure evil".
After the hearing she said: "We knew Dunlop was responsible and my husband and I were determined not to rest until he had been brought to justice.
"It's been a long and difficult journey to see him standing in the dock.
"He's done everything he could do to avoid justice, but his lying and scheming have eventually all been in vain.
"We made a promise to ourselves that Julie's killer would be punished and everyone we have approached over the years has helped me in some way to reach that goal.
"No-one can know what it is like to lose a daughter in such horrific circumstances. Our family will live with her death forever."
The Crown Prosecution Service area head Martin Goldman said: "William Dunlop has tried to escape responsibility for nearly 20 years and has put Julie Hogg's family through great suffering.
"Today, we have finally seen him accept that he, and he alone, was responsible for killing Julie and hiding her body behind a bath panel where it was discovered by her mother."
The case was adjourned for sentencing on 6 October.
Afterwards, Cleveland CPS chief Martin Goldman said: "We will be putting to the court that Billy Dunlop is an evil and very violent man and will be asking the court to sentence him on that basis."
The law change only applies to England and Wales. In Scotland the old double jeopardy rule still applies.