Lewis Power QC for Ashdown said there were no issues around his fitness to plead before the 20-year-old answered guilty to the charge of murdering his friend.
“He knows it’s a life sentence,” Mr Power said.
“He will say he did not pre-plan the murder but at the scene he did form the intent and he did carry out that murder.”
Marc’s heartbroken family paid tribute to the cheeky boy who never returned home from a night out with his friends in May this year.
His family said: “Marc touched the hearts of so many people, and made their lives brighter with his loving, caring and thoughtful actions.
“We are feeling his loss every second and that will never change.
“Our hearts are broken.
“Rest peacefully, our cheeky boy.
“With so much love from Mum, Dad and your whole family.”
Ashdown pleaded guilty to murder between May 28 and May 31 this year.
He also pleaded guilty to having an offensive weapon.
He will be sentenced next month.
Twenty-year-old admits murdering his friend by stabbing him more than 100 times