THE man accused of murdering Helen Scott and Christine Eadie is one of Scotland's most violent criminals.
Angus Sinclair's crimes, details of which were kept from the jury, include the murders of two girls aged eight and 17 and numerous child rapes.
Police also suspect he may have been involved in other unsolved crimes.
A Jekyll-and-Hyde figure, Sinclair was someone who could be polite and even charming but would resort to brutal, extreme violence, often to satisfy sexual demands.
Born in Glasgow on 7 June, 1945, the son of Angus and Mary, Sinclair was brought up in a council home in St Peter's Street.
The youngest of three children, he had a fairly typical working-class upbringing.
Sinclair was 13 when he committed his first offence, stealing a collection box from a church in Glasgow. But as he grew up, Sinclair's offences became more sinister as he developed a pattern of sexual offending towards children.
On 20 January, 1961, aged 15, he was convicted at Glasgow Sheriff Court of lewd and libidinous practices towards an eight-year-old girl, and placed on probation for three years.
Later that year, Sinclair lured eight-year-old Catherine Reehill into his home, sexually assaulted her, strangled her to death and threw her body over the stairwell balcony.
Passing sentence, Lord Mackintosh described Sinclair as "callous, cunning and wicked" and said Sinclair was so obsessed with sex that he would not even stop short of taking a life to gratify his lust.
However, he spent only seven years behind bars for the crime. Sinclair later settled in Edinburgh's Southside, where he met his future wife, Sarah Hamilton.
He and Sarah moved to Glasgow in 1972 and had a son, Gary, the following year.
At the time of the World's End murders, Sinclair and Sarah lived in Horndean Crescent, sharing their home with Sarah's brother, Gordon.
He and Sinclair would often go on weekend fishing trips in a Toyota Hiace van Sinclair had bought. Sarah later told police that they never came back with any fish.
In 1979, Sinclair was convicted of illegally possessing a firearm and ammunition and sentenced to nine months in prison.
Around this time, Sinclair committed a string of rapes and indecent assaults against children, both boys and girls, aged from eight to 12. In total, he was thought to have carried out an estimated 20 to 30 child sex attacks.
While serving a life sentence at Peterhead Prison, it emerged that Sinclair had murdered 17-year-old Mary Gallagher in Glasgow in 1978.
She was raped and stabbed near a railway line as she went to meet a friend.
Sinclair was successfully convicted in 2001, after new DNA evidence extracted from a hair linked him to the crime.