A 17-year-old boy tapped a kitchen knife on his leg a number of times before he lunged forward and stabbed a student in the neck in Cork last January, the Central Criminal Court heard today.

The teenager has pleaded guilty to the murder of 20-year-old Cameron Blair, who tried to act as "a peacemaker" at a house party on Bandon Road on 16 January.

The biochemistry student had earlier allowed the accused and his two friends into the party.

He also acted as a "good Samaritan" when he brought a drunk sleeping homeless man into the house because he was concerned about him.

The court also heard that Cameron did not realise he had been stabbed and laughed it off before he collapsed and later died.

His final words were "don't worry lads, I don't want to be fighting", before he smiled and closed his eyes.

Defence counsel Brendan Grehan read an apology from the 17-year-old in which he said he was "deeply remorseful" for what he had done.

He is due to be sentenced later this month.

Cameron was a sportsman, a rugby player, a student in Chemical and Biopharmaceutical Engineering and a black belt in karate.

The 20-year-old went to a student party at a house on the Bandon Road in Cork on 16 January this year and agreed to watch the door.

The 17-year-old who killed Cameron arrived with an 18-year-old, a 14-year-old and a drunk homeless man and although the others in the house did not want to admit them, Cameron said they were "tome" which means "sound" and let them in.

The three drank with the students inside but at one stage went into the kitchen and armed themselves with knives. 

The court heard they had become paranoid.

One of the students got them to arrange a cannabis deal for him and bought €50 worth, another got worried and got them out of the house by telling them the party was finishing and that everyone was going into town.

The 17-year-old had the large kitchen knife down his trousers and got one of the students to buy him more drink at the off licence. 

When he returned to the house, Cameron was at the door preventing them from getting back in.

The court heard he was "acting as the peacemaker and trying to keep the situation calm".

A number of students called gardaí and said there were men outside with knives trying to get in, but Cameron insisted they were "sound".

He said to one of the three "will you tell your friends to relax" and shook his hand.

CCTV footage of the murder was also shown to the court.

Detective Sergeant Martin Canny said that the 17-year-old "paced up and down" and "tapped the knife on the back of his leg" a number of times before he lunged forward in a downward motion and stabbed Cameron once in the neck.

The accused waited around 12 seconds before he ran and caught up with the 18-year-old and a group including those who had sold the student the cannabis.

The 14-year-old ran in another direction. Gardaí saw them running away as they rushed to the scene.

The 17-year-old had been wearing gloves and threw them and the large kitchen knife, the murder weapon, down a steep embankment that night before going to stay with his grandfather.

The area was described in court as "impenetrable" and it took gardaí two days to recover the items. 

His DNA was found on the gloves while Cameron's was found on the knife.

When asked for his clothes, he first gave gardaí a different set other than those he was wearing on the night, but when they retrieved them Cameron's blood was found on the boy's jacket.

Cameron's parents and brother gave victim impact statements in court today. 

His mother Kathy said she screams at the injustice of this, she is no longer living, only existing, and that positivity and kindness came naturally to Cameron. 

"The price of immense love is immense grief when that person is taken from you" she said, "we will be paying that price for the rest of our lives," she said.

Noel Blair said the sight of his son on a trolley will haunt him to his dying day, adding "the full weight of what you have taken hits me hard".

He said: "The death of a son is described as the ultimate grief and I now know this to be true."

His brother Alan said he stares in disbelief at Cameron's name on the plaque in the graveyard.

"You have robbed me and my brother of his life," he said. 

He also said Cameron wrote a wish list that he was ticking off, which included learning to drive, studying and living to 100.

In his apology, the 17-year-old said Cameron "was nothing but nice to me on that night".

"He did nothing wrong to me. I think about that night first thing in the morning and last thing at night. If only I could turn back the clock and walk away. I will never forgive myself."

Mr Justice Paul McDermott said cases where a juvenile is convicted of murder do not attract the mandatory life sentence appropriate to an adult.

He said the court has to consider the appropriate sentence to be imposed under the Children's Act 1908 and could dispose of the case today.

The judge said he was sorry the case cannot be brought to a conclusion today and put it back until later in the month.