Trevor William Hamilton was born on 19 June 1982 and raised in Sion Mills, County Tyrone, Northern Ireland. He was described by residents of the area as a "depraved loner", with a documented IQ of 68, suggesting borderline intellectual functioning. From a young age, Hamilton engaged in increasingly disturbing sexual behavior. In his teens, he became known to local law enforcement for repeatedly exposing himself to women while masturbating along rural roads. He was convicted of five counts of indecent exposure in December 1999, resulting in a sentence of two years' probation.

Hamilton, who did not possess a full driver’s license, frequently cruised the back roads of Sion Mills, often evading police. He later claimed he was locally nicknamed "The Bandit" for his ability to escape detection.

On 16 February 2000, at age 17, Hamilton committed a brutal and premeditated rape. He offered 29-year-old Helen Harpur a lift into Newtownstewart but instead drove her to his family home on Concess Road. There, he strangled and dragged her by the hair into a caravan and raped her for over an hour while beating and threatening to kill her. The attack ended only after he ejaculated and forced her to swear on her son's life not to contact the police. Despite this, she reported the assault immediately. Police found Hamilton removing the plates from his car and attempting to alter his appearance by shaving his head. Forensic evidence and victim testimony linked him definitively to the crime.

Although he initially denied the charges, Hamilton changed his plea to guilty as the trial opened in March 2001. A pre-sentence report noted that while his IQ was low, he understood right from wrong and had "major difficulties in controlling his sexual urges." Originally sentenced to four years in a young offenders’ institution and three years' probation, the Attorney General appealed the leniency of the sentence, and it was increased to seven years imprisonment.

Hamilton was released on licence in mid-2003 after serving only half his sentence. He was assessed as high-risk (level 3) to the public, particularly to adult women.

On 11 December 2003, Trevor William Hamilton abducted and murdered 65-year-old Attracta Harron. She was returning from Mass in Murlog, Lifford, County Donegal. At the time, Hamilton had recently been released from prison after serving half of a seven-year sentence for rape and other offenses. His risk assessment indicated a high danger to the public, particularly adult women.

Attracta Harron's body was discovered on 5 April 2004, four months after she was last seen. Her body was hidden in a riverbank less than 50 yards from Hamilton's home. Investigators connected him to her disappearance and arrest followed.

Hamilton was found guilty of her murder on 12 April 2006. During the sentencing on 4 August 2006, the trial judge recommended that he should never be released from prison. This was a notable decision in Northern Ireland, though similar sentences have been given in England and Wales.

On 27 June 2008, the Court of Appeal revised the sentence, ruling that Hamilton would have to serve 35 years in prison before he could be considered for parole. This decision meant that he would likely remain incarcerated until at least 2040, when he would be 58 years old.

In 2006, a serious case review was conducted regarding Hamilton's crimes. Later that year, while in Maghaberry Prison, he was attacked and beaten by another inmate. Throughout this time, Hamilton maintained his innocence concerning the murder of Attracta Harron.