Gangland killer Nathan Killeen is challenging his 23-hour lock-up regime at the Midlands prison.
The 25-year-old from Hyde Road, Prospect in Limerick is serving life for the murder of businessman Roy Collins who was gunned down at the Roxboro Shopping Centre in 2009.
The court heard convicted killer Nathan Killeen was placed in isolation at the Midlands Prison on May 3, and remains on 23-hour lock-up.
The Midlands Prison.
His laywers say his punishment is arbitrary because the prison authorities have failed to provide any reasons for his solitary confinement other than that his behaviour is a threat to the maintenance of good order.
Barrister Micheál O'Higgins conceded Nathan Killeen was caught with drugs in prison two months ago but he said no disciplinary proceedings have been brought against his client.
Judge Raymond Fulham has given the prisoner permission to bring a full legal challenge to his continued segregation on grounds that it is allegedly in breach of prison rules and fair procedures.