Harold Shipman was an enigma, and police struggled to understand him. Officers were given the picture of a hard-working GP who commanded the respect of his patients at his surgery in Hyde, Greater Manchester.
But as they delved deeper into his background, speculation grew that events in his formative years had turned him into a killer.
Born on January 14th, 1946, to a working-class family in Nottingham, Harold Frederick Shipman was known as a clever, confident child. He passed his 11-plus and secured a place at the city's High Pavement Grammar School, but was also seen as a loner.
In 1963, when he was 17 and studying for A-levels, his mother, Vera, died at the age of 43 from lung cancer, the pain of her last days helped by large doses of morphine.
The trauma of the bereavement and his closeness to his mother, his inability to form meaningful relationships and his arrogance could have combined with his need for control to give him a perverted pleasure from causing death.
After leaving school, Shipman studied at Leeds University Medical School in 1965 and, while in lodgings in nearby Wetherby, began going out with a farmer's daughter, Primrose Oxtoby.
Primrose became pregnant, and the couple were married during Shipman's first year at university.
He graduated in 1970, becoming a houseman at Pontefract General Infirmary in West Yorkshire, before joining his first practice in Todmorden, in the Pennines.
It was there he began forging prescriptions to supply himself with the painkiller pethidine, which he injected for six months to the point where his veins collapsed.
When his drug habit was discovered, he resigned immediately. He was later fined £600 at Halifax Magistrates' Court on drugs and forgery charges.
But despite his case coming before the General Medical Council, he was not struck off or even censured. It was only three days before his murder conviction nearly 30 years later that the GMC, the medical profession's disciplinary body, discovered the records of the conviction in their files.
He underwent a course of psychiatric treatment and returned to work as a medical officer in Durham before moving to the Donneybrook practice in Hyde, setting up home in nearby Mottram with Primrose and their four children.
Mrs Shipman, who worked with her husband as a part-time receptionist, and their children, Sarah, Christopher, David and Sam, stood by the GP throughout his arrest and trial.
The case two years ago saw Shipman receive 15 life sentences and a recommendation from the judge, Mr Justice Forbes, that he should never be released.