BROTHERS John and Desmond Dundon, who are serving life sentences for murder, have mounted a legal challenge to being housed in the segregation unit at Portlaoise Prison.
The brothers' lawyer told the High Court that they, along with a third man, Nathan Kileen, are on a 22-hour lock-up in "the block".
Micheal P O'Higgins asked why segregation required a denial of education and gym facilities and vocational training. He was opening the challenge brought by the Dundons and by Kileen, seeking orders that their continued detention be declared unlawful.
John Dundon (29), Hyde Park, Limerick, was jailed for life last August after being convicted of the murder of rugby player Shane Geoghegan at Dorradoyle in 2008 in a case of mistaken identity.
Desmond Dundon (31) is serving a life sentence for the murder of rival Limerick crime boss Kieran Keane in 2002.
Nathan Kileen (22), also from Limerick, is serving a five-year sentence for violent disorder.
The case continues.