Gardai at the scene of the knife attack at the seafront in Dun Laoghaire

A 15-year-old boy who cut a woman's throat after meeting her through a social media app spoke in a "calm and controlled" voice during the attack, the Central Criminal Court has heard.

The youth had brought the victim (25) to the seafront in Dun Laoghaire to take a selfie when he put her in a chokehold and began knifing her, cutting into her windpipe.

The boy (now 16) has pleaded guilty to attempting to murder the woman, Stephanie Ng, at Queen's Road, Dun Laoghaire, on December 23, 2017.

Mr Justice Michael White adjourned sentencing after hearing a psychiatric report on the accused would be needed.

Psychopath

Det Gda Daniel Treacy said that when the boy and victim made contact through the Whisper app, he held himself out as being 19-years-old.

The accused asked the victim to participate in a threesome and she declined, making it clear to the accused that she was not interested in any form of sexual relationship with him.

He set out that he could not commit to girls, telling her "it's like being a psychopath, you don't feel it so it's pretty crazy feeling it for the first time".

He told her he had not developed feelings for anyone and had not had a crush on anyone, the court heard. They arranged to meet in Dun Laoghaire on December 23.

He indicated to her that "he would bring her to a secret spot" and she jokingly said it sounded like "he was going to murder her", the court heard.

He replied that he "did not think he could murder her".

They met at the entrance to Dun Laoghaire Shopping Centre that afternoon and their movements were tracked on CCTV.

He first brought her to a derelict house at York Road, asking her to come in and she declined. He was not able to gain entry anyway as it was boarded up.

He suggested they go to another derelict house and she again said no. The pair made their way to the seafront promenade, where she declined to go with him into the disused baths.

At his suggestion, they went to the lower path near the water's edge to take a selfie.

Ms Ng was facing out to sea when she was grabbed from behind by the accused, who put her in a neck lock and started choking her with his right hand, while brandishing a knife in his left, Det Gda Treacy said.

The victim raised her hand to protect herself and to try to catch a hold of the knife.

She suffered "significant lacerations" and the accused told her to stop screaming. He did this in a "calm and controlled voice".

The victim urinated as a result of the attack and the shock she was in, and passed out because of the stranglehold.

When she came around, Ms Ng was lying on the ground near the water's edge. Her hand was bleeding and there was blood around her head.

Det Gda Treacy said Ms Ng did not know if she realised then that her throat was cut or when she got to the footpath, where she collapsed.

People out walking noticed her and came to her assistance.

They saw she was very pale, her lips had gone blue and she was unable to speak.

One of those who helped her thought she was going to die.

Emergency services arrived and she was taken to St Vincent's Hospital.

She had a large 10cm-deep slash wound across her lower neck, from one side to the other, which cut through the trachea 75pc and damaged her voice box.

She also had stab injuries on her upper right arm and the base of her right thumb. In the thumb wound, the blood flow had been compromised and tendons were severed.

She had suffered significant blood loss and had aspirated blood into her lungs. Ms Ng was put into a medically induced coma so she could be treated.

Identified

The next day, she showed gardai her app messages and her attacker was identified.

The accused was arrested at his home on Christmas Day.

When gardai arrived, he was in his bedroom and said: "Is this about the stabbing of that girl? I haven't got the knife, I threw it in the ocean."

Gardai seized a book of drawings that included an entry on November 17, 2017, which "appears to show someone being cut up with a knife".

There was an entry with a reference to "serial killer might also be self-deprecator, self-praiser."

Gardai found the boy had deleted the Whisper app around midnight on December 24-25.

He had also carried out web searches about the stabbing.

The blood on his Leinster rugby backpack was a match for Ms Ng's.

Det Gda Treacy said there had been a "huge amount of pooling of congealed blood" at the scene, which suggested Ms Ng had been there "a while".

The victim was an Irish national living in South Dublin and working at two jobs at the time, said Paul Burns, prosecuting.

Patrick Gageby, defending, said the accused's school attendance in 2017 had been sporadic, "possibly due to mental health issues".

The boy, wearing a navy jumper, white open-necked shirt and blue jeans, was in court with his parents, who sat alongside him in the dock. His mother hugged and kissed him before and after the hearing.

He was remanded in custody.