Gerard McKerr, one of the 'Hooded Men', whose treatment during interrogation in Northern Ireland in 1971 is back before the European Court of Human Rights, has died.
Mr McKerr, who was 71, died in the early hours of the morning after being taken to hospital on St Patrick's Day.
He is survived by his wife Eileen, three children and eight grandchildren.
Mr McKerr's graphic account of his interrogation featured in last year's RTÉ Investigation's Unit documentary The Torture Files.
New evidence revealed in the programme led to the decision by the Government last December to apply to the European Court of Human Rights to revise its judgment in the 1978 inter-state case, Ireland v United Kingdom.
The hooding, white noise, enforced wall standing and sleep, food and water deprivation of the 14 Hooded Men was central to that defining judgment on what constitutes torture.
The programme revealed that members of the British cabinet had sanctioned the use of the torture methods and that evidence was withheld in the case by the UK.
Mr McKerr had battled illness for several years. Just over a year after his interrogation, he developed Hodgkin's disease, a form of cancer.
Sinn Féin leader Gerry Adams has expressed his condolences and sympathy to the family and friends of Mr McKerr.
Speaking from the United States where he is involved in a series of political engagements, Mr Adams said, he was "saddened to learn of Mr McKerr's death at his home in Lurgan on Thursday this morning."