A two-year old girl murdered by her mother's on/off boyfriend was killed in a "gross, cruel, brutal and catastrophic" act which was "totally devoid of humanity upon a defenceless and vulnerable child."

Ali Jayden Doyle died from a severe head injury she sustained in a house in the Park Avenue area of Dungannon in August 2021.

The toddler was murdered by Darryn John Armstrong (35) who initially blamed Ali Jayden's one-year old brother for causing the fatal wound by throwing a plastic toy at her which caused her to fall against a fireplace.

The murder occurred in Armstrong's home and Belfast Crown heard that the two children had been left in his care by their mother Jade Dempsey - which was in breach of a Child Protection Plan imposed by social services which banned Armstrong from having contact with the youngsters.

He has 77 previous convictions includes charges of domestic abuse and was the subject of a Probation Order when he murdered Ali Jayden.

Despite his initial claims, Armstrong later admitted that on the morning of August 6, 2021 he had Ali Jayden in his arms and that he threw the child who hit her head on the fireplace.

He also admitted that he was under the influence of cannabis at the time, was 'frustrated' and lost his temper.

Armstrong, whose address was given as HMP Maghaberry, was handed a life sentence in May after he admitted murdering Ali Jayden.

Dempsey (28), whose address is the subject of a reporting restriction, wasn't present when her daughter was killed as she was due to travel to Belfast to buy a double-buggy.

She pleaded guilty to wilfully neglecting and exposing Ali Jayden Doyle in a manner likely to cause unnecessary suffering or injury to health on August 6, 2012.

Both defendants will be sentenced on the charges at a later date by Mr Justice McAlinden.

During today's plea hearing, the senior judge was addressed by a Crown barrister as well as defence barristers representing both Armstrong and Dempsey.

Crown barrister Ciaran Murphy KC said Ali Jayden was murdered some time between 10.45am - when Armstrong sent Dempsey a video on WhatsApp of the toddler sitting on the sofa - and 11.04am when Armstrong called 999 for an ambulance.

Mr Murphy said that during this timeframe, a neighbour of Armstrong's heard the sounds of children "screeching" and "crying" coming from his property.

When the paramedics arrived, Armstrong said Ali Jayden's brother had thrown a toy at his sister which caused her to fall and hit her head on the fireplace and that this had occurred whilst he was in the toilet.

They were led to a bedroom where they located Ali Jayden who lying on a bed and covered with a towel and with wet hair.

Armstrong - who was described by paramedics as 'frantic' - said he had to call Dempsey, who arrived a short time later after running back to the scene from the bus stop.

He also told medics that he had thrown a cup of water round Ali Jayden in a bid to rouse her.

Mr Murphy said a doctor then arrived at 11.39am and noted that Ali Jayden was 'extremely unwell'.

She was transferred via ambulance to the Royal Victoria Hospital and arrived, with her mother, at 12.20am.

Despite the best efforts of medical staff at the hospital, the child was pronounced dead at 4.20pm and a subsequent post mortem concluded she sustained a severe head injury caused by impact against a solid surface.

The Crown KC told Mr Justice McAlinden that those who treated Ali Jayden determined that the nature of the fatal head injury was not compatible with Armstrong's version of how they occurred.

Following his arrest on suspicion of murder, Armstrong reiterated his claim that Ali Jayden has fallen and hit her head after her brother threw a toy at her and denied he caused the injury.

He subsequently admitted her murder and in a defence statement compiled in February, Armstrong provided an account which stated he was in the living room with Ali Jayden in arms.

Armstrong claimed his dogs came into the room and started 'going hyper', the two children 'started to scream' and that he 'threw' Ali Jayden who 'hit her head on the fireplace.'

The prosecutor said that when this statement was shown to Crown experts, one medic noted the severity of head injury and indicted "how he can envisage a scenario whereby the child was perhaps gripped by the torso and then with great force is swung, or slammed, or shaken against an unyielding surface."

This same expert added that impact head injury which killed Ali Jayden was akin to being  sustained in a high-speed traffic accident or a fall from a great height.

Mr Murphy said that whilst there was "no definite account" of what Armstrong did, "suffice it to say, on any assessment it was gross, cruel, brutal and catastrophic .. and it must rank as an action that was totally devoid of humanity upon a defenceless and vulnerable child in circumstances were he was left in a position of trust in relation to the child, despite the obvious reasons that he should not have been."

Mr Justice McAlinden was then addressed by Brian McCartney KC, who represented Armstrong and who said his client accepted responsibility for what he did.

Describing Armstrong's upbringing and background as "dysfunctional", the defence barrister said this included periods in foster care and attending specialist schools.

Armstrong's barrister Brian McCarney said Armstrong was born in Enniskillen and live there until he was aged 14. Following problems within his family he then moved to England.

He added that he attended special schools in Enniskillen and Omagh

Mr McCartney also spoke of Armstrong's "long-standing history of abusing both drugs and alcohol."

Dempsey's barrister Gavan Duffy KC revealed she had been the victim of domestic abuse in the past and whilst accepting she breached the social service plan which banned Armstrong from having contact with her children, she "relives the consequences" every day.

Highlighting the trauma and "life-long" impact she will suffer due to the "murder of her daughter", Mr Duffy added that she has already served a 12-month period on remand.

After listening to the submissions, Mr Justice McAlinden noted that both defendants "ignored" the social service Child Protection Plan which resulted in "tragic consequences."

He added that he needed time to reflect on what he had heard and would pass sentence at a later date.