Police began investigating sickening sex attacks attributed to Peter Chapman when he was just 15 years old.
Over the next 18 years he carried out a string of sexual assaults and rapes in different parts of the UK before being jailed in 1996.
To many he portrayed himself as a meek and mild individual, but police described him as devious and dangerous.
It was in late 2009 that he used an online photo of a handsome young man to attract Ashleigh Hall to her death.
He has been sentenced to life in prison after admitting her kidnap, rape and murder.
Chapman was born in January 1977 and brought up by his grandparents on the Hardwick Estate in Stockton.
In 1992, aged 15, he was the subject of a sexual assault investigation and four years later was accused of raping a girl he had befriended who became pregnant, although the allegations were later dropped.
But in December 1996 he found himself in court accused of attacking two teenage prostitutes.
He had stolen a car, fitted it with false number plates and cruised the streets of Middlesbrough before picking up a 17-year-old street girl, driving her into County Durham and raping her at knife point.
Two days later he did exactly the same thing to another prostitute.
Chapman was sentenced to seven years and on his release in 2001 moved to Merseyside where he had befriended a woman and moved in with her.
In 2002 he was arrested by Cheshire Police for the rape and kidnap of a prostitute in Ellesmere Port. The case was discontinued.
By June he had moved to Bristol, where he was arrested for deception offences and in February the following year was arrested in Liverpool for the rape and kidnap of a prostitute.
He had enticed her into his car and, because of his "meek and mild" looks and manner she agreed to go to a house where he kept some money.
It was there he produced a knife, tied her up, kept her prisoner for 14 hours and raped her. He was charged and remanded in custody, but the case was later discontinued.
Det Insp Mick Callan, head of Durham's Major Crime Squad, said: "She told police that at first she didn't feel threatened because of his manner.
"The truth is he is anything but meek and mild. He is a devious and dangerous individual and could well be responsible for other, similar offences."
In December 2007 he became linked to a single mother in the Runcorn area of Cheshire and moved in with her.
Ashleigh Hall had been smothered and dumped in a field
Chapman failed to comply with his sex offender conditions and the woman, who had a young baby, was informed of his past. She threw him out.
In 2009 he moved to the Thames Valley where he befriended another woman, but soon fell out with a neighbour whose house was later destroyed by fire.
Chapman disappeared shortly after the blaze, taking with him a laptop computer he had stolen. He eventually turned up back on Teesside last October having bought a car using his Runcorn ex-girlfriend's details.
He was living for a time at the Metro Hotel close to the A19 in Stockton and was very active on the stolen computer.
Sometime in late September or early October Ashleigh was attracted by a picture of a handsome young man that Chapman had posted on the web.
He pretended to be that young man and called himself Peter Cartwright. As such he was accepted as a friend by Ashleigh Hall whom he later raped and murdered.