A teenage boy used a sledgehammer and a lump hammer to bludgeon 51-year-old Lorna Woodnutt to death.
He then posted a video on Snapchat and sent a selfie with the victim's faceless body, his trial has heard.
The victim's niece told the Central Criminal Court on Monday how she discovered her aunt had been brutally murdered when she received content that she described "as something a terrorist would create".
The boy told detectives he recorded and shared the video on Snapchat with "everyone in his contacts", which the court heard was "a three-figure number" so officers "would come".
His Snapchat friends could view the video for 30 minutes before the teen took it down when gardaí arrived, the court was told.
The court also heard during Monday's sentence hearing that the now 17-year-old defendant, who cannot be identified because he is a minor, was diagnosed with autism spectrum disorder at 18-months-old and there had been an increase in his aggressive and oppositional behavioural issues towards staff and students in his school in the weeks leading up to the killing.
Laboratory technician Ms Woodnutt had suffered fatal blunt force injuries to the head, face and chest in the attack when she was sitting at a kitchen table working on her computer.
A post-mortem examination report revealed that Ms Woodnutt's facial features were absent, with a defect in the face exposing the skull "without any extracranial content present". There was a loss of the anterior facial skin and soft tissue from the forehead to below the chin.
The boy appeared in court for his sentence hearing having pleaded guilty earlier this month to murdering Ms Woodnutt (51) at a property in a rural area outside Tullamore, Co Offaly on September 29th, 2023.
The court heard another boy had described opening the Snapchat video in his statement to gardaí, which was posted by the defendant at lunchtime that day.
The boy saw a body in the video with "feet up on a couch and a face with a big hole". A sledgehammer and a lump hammer were beside the victim's body in the video, the court heard.
The defendant had also sent this boy "a selfie" with Ms Woodnutt's body in the background and a caption.
'I did it'
The boy called 999 on two occasions after he murdered Ms Woodnutt, and gardaí also received a phone call arising out of the video posted online.
When the garda asked the defendant who else was with him, he nodded in the direction of Ms Woodnutt's body, saying: "Her, I did it."
In his interviews, the teenger told gardaí he got angry and had "lost the head" when he had an argument with Ms Woodnutt.
"Now I regret it as I'm stuck here. I just whacked her, I don't know what got into me, it just built up over the years," he added.
The defendant also told gardaí: "I hit her as hard as I could, 20 to 30 times. I normally wouldn't do this kind of thing, it isn't me".
The boy said he "came at" Ms Woodnutt with a hammer and had "overpowered" her. He said he could see she was still breathing on the ground, so "kept going until she stopped".
He also said he had put the video on Snapchat as he knew gardaí would not want "me to do that".
An analysis of the boy's phone revealed Google searches about hammer attacks, Garda abilities to track phones and searches about the behaviour of psychopaths, the court was told.
In an emotional victim impact statement read to the court, the deceased's niece, Jessica Woodnutt, said she discovered her aunt had been brutally murdered when she received a video "with content that I can only describe as something a terrorist would create".
The now 20-year-old added: "My legs turned to jelly. I was home alone.... I could not watch the entire video and only clicked into it to find out it was actually Lorna who had been murdered, hoping that it was some sort of mix up.
"Her head was destroyed, and her beautiful face was no longer there. Instead, at her shoulders was a pool of blood. I was immediately distraught and entered a state of denial.
"I phoned the local Garda station and asked that they check on my auntie... I feared this video was being mindlessly shared on social media as my auntie lay lifelessly at her home without help.
"The guards could not tell me much over the phone but just said that they were looking into something at this time but could not reveal details. This was enough to confirm to me that I was in fact living in what could only be described as my worst nightmare," Ms Woodnutt said.
Alison O'Riordan
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