Prosecutors claimed Timothy Walker, 39, inflicted multiple blows to Denis Shearer’s head with a blunt object as the victim lay in bed at a house in Bangor.
Walker, of Abbey Ring in Holywood, faces charges of murder and aggravated burglary. His partner, 38-year-old Natalie Brannigan, is accused of assisting him in events surrounding the attack on February 28.
Details emerged as the couple were refused permission to drink alcohol and extend their bail curfews for Twelfth of July celebrations.
Mr Shearer, 25, died in hospital nine days after being assaulted at a property on Fernmore Road.
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Crown lawyer Iryna Kennedy told the court: “He was killed as he lay in bed in his foster parents’ house.
“The post mortem concluded that the cause of death was blunt trauma of the head due to multiple blows from a blunt instrument.
“It is the (prosecution) case that was done by Timothy Walker.”
Walker allegedly fled from the scene, with the help of Brannigan, but was arrested on March 2 after voluntarily attending a police station.
During police interviews he stated that he could not remember his movements due to alcohol consumption and cited mental health issues, the court heard.
Mrs Kennedy said: “He did say that he heard voices in his head and he said voices in his head told him to ‘get him’, that is the victim, and that he had been drinking.”
Brannigan, with an address at The Green in Holywood, is a cousin of the victim.
She had previously made a complaint to police about Mr Shearer which may have provided a motive for the attack, according to the prosecution.
The court heard she allegedly collected her partner and drove him away in a bid to evade detection.
“Natalie Brannigan admitted that when Timothy Walker got into her car she said she confronted him and he stated that he had Denis ‘done’,” Mrs Kennedy added.
Opposing the couple’s bid to vary their bail terms, counsel claimed there had been heavy drinking at a party before Mr Shearer was targeted.
Defence lawyers stressed a limited relaxation was being sought so they could attend an eleventh night bonfire and family barbeque on the twelfth.
But denying both applications, Mr Justice Horner ruled: “I do not consider it appropriate to vary their conditions of bail, given the seriousness of the charges and the involvement of alcohol in the original murder.