A convicted murderer has won an appeal against being put in solitary confinement for an attack on a sex offender held in the same jail.

Darren Hart, who is serving a life sentence for stabbing a teenager to death in Newry, Co Down, was challenging a decision to detain him in the Special Supervision Unit at Maghaberry Prison.

Hart (23) was segregated after a governor was told he had been a ringleader in the serious assault in November 2007.

The killer’s application for a judicial review of this and other decisions was previously dismissed in the High Court.

But three judges sitting in the Court of Appeal yesterday backed his case that it was wrong to confine him for the attack under a section of the Prison and Young Offenders Centre Rules (Northern Ireland) Order 1995 which permits the separation of a prisoner who is to be charged with an offence against discipline.

“We must allow the appeal to the extent of declaring that the decision purporting to have been made under Rule 35 (4) to keep the appellant separate from other prisoners was bad in law,” Lord Justice Girvan said.

Hart was jailed for stabbing 18-year-old Brendan McCabe, pictured, in front of the victim’s mother at Canal Street, Newry in February 2002. At the time of the murder he was aged 16.

Both teenagers were from the Mourneview Park estate in the city.

Hart’s legal team argued that the rule allowing the governor to order his confinement for the assault only comes into play, pending adjudication, when it has been decided that charges are to be brought.

Judges were told there was no evidence to suggest that Hart was ever going to be charged with an offence against prison discipline in connection with the assault on the sex offender.

They decided to allow his appeal only to the extent that there was no power to separate him from other prisoners under Rule 35(4).

Hart did not challenge other aspects of the High Court judgment which upheld an adjudication decision where he was found guilty of attacking another prisoner a day earlier and given seven days cellular confinement.

With costs also awarded against the Prison Service, Hart’s solicitor, Fearghal Shiels of Madden and Finucane, claimed the case had important implications for prison governors.

“Rule 35(4) of the prison rules provides for the detention of prisoners pending an adjudication,” Mr Shiels said.

“There was no evidence to suggest that our client was ever going to be charged with an offence against prison discipline.

“This decision has important implications for the manner in which prison governors, to date, have been effectively able to penalise prisoners in circumstances not expressly provided for by the prison rules.”