Born in County Carlow, Ireland, O'Carroll gained notoriety in 1980 when he published Paedophilia: The Radical Case, a book that pushed for the normalization of some adult-child sexual relationships. In the book, O'Carroll argues that each stage of the sexual relationship between an adult and child can be 'negotiated'
by hints and signals, verbal and non-verbal, by which each indicates to the other what is acceptable and what is not... the man might start by saying what pretty knickers the girl was wearing, and he would be far more likely to proceed to the next stage of negotiation if she seemed pleased by the remark than if she coloured up and closed her legs.
In 1981 he was convicted for "conspiracy to corrupt public morals" over the contact ads section of the PIE magazine and was imprisoned, and once again in 2002 on charges of evading a prohibition on the importation of indecent photographs of children stemming from nude photographs that O'Carroll had taken of children on the beaches of Qatar. At the time, he was working on a book about the musician and philanthropist Michael Jackson who was later acquitted of charges brought against him regarding indecent behaviour towards a child.
Later, O'Carroll was arrested once more on suspicion of conspiring to distribute indecent photographs of children after supplying an undercover Met police officer who infiltrated the pedophile advocacy groups with a cache of child pornography obtained from his co defendant, Michael John De Clare Studdert's vault of 50,000 pornographic images. He was arraigned 1 June 2006 on child porn charges. In September 2006, he admitted to two counts of distributing indecent images of children.
In December 20 2006, he was jailed for 2½ years at London’s Middlesex Crown Court.