A letter from Ibrahim Halawa has been smuggled out of the Egyptian jail where he's been held for three years.
The 20-year-old from Firhouse in Dublin was arrested taking pictures of a Muslim Brotherhood protest while on holiday in Cairo in 2013.
Mr Halawa’s letter, which has been seen by the Irish edition of The Times newspaper, claims he has witnessed torture in jail.
He says inmates are strung up, with people hung from basketball hoops and “crucified” in hallways.
Ibrahim, who was 17 when he was arrested, faces the death penalty as he awaits the verdict of his mass trial on 29 June.
The trial has been postponed more than a dozen times.
Amnesty International has named him a prisoner of conscience and the Irish Government, the European Parliament, and the United Nations have all called for his release.