The jury in the trial of a teenager accused of murder by stabbing a 16-year-old to death in an Aberdeen school has retired to consider a verdict.
Bailey Gwynne died after being stabbed in the heart at Cults Academy last October.
The 16-year old accused, who cannot be named for legal reasons, denies murder at the High Court in Aberdeen.
Judge Lady Stacey told the jury the question was whether the accused was guilty of murder or culpable homicide.
Advocate depute Alex Prentice QC, prosecuting, told the jury during his closing speech at the High Court in Aberdeen: "Bailey Gwynne had no chance."
He said: "This was a lethal wound inflicted by a lethal weapon."
He said it was a "silly trivial fight between two schoolboys".
Knife and knuckleduster
Mr Prentice started by asking the jury: "Why do you think a young man would carry a knife and a knuckleduster?"
He added: "You would have to have hearts of stone not to be moved by the emotion of this trial, but you must put emotion aside."
Mr Prentice asked the jury to convict the accused of murder, but added they could convict of the lesser charge of culpable homicide.
He also asked for guilty verdicts on the two charges of having knives and knuckledusters in school.
Mr Prentice said: "There was a stab wound to the heart inflicted by a lethal weapon that was routinely carried.
"It may be everyone in this room wishes they had the power to turn back time.
"If we could do that, what would we do? We would say 'get rid of the knife, school is no place for a knife'.
"This case demonstrates the dangers of carrying a knife. If you have a knife you have the ability to use it."
Mr Prentice said he did not suggest the accused set off intending to kill Bailey Gwynne.
But he added: "If he had not been carrying a knife the outcome of the conflict would have been a few bruises and perhaps a fat lip."
Defence counsel Ian Duguid QC said the jury was dealing with a "spontaneous event" which lasted about 30 seconds.
Mr Duguid said the accused had shown "extraordinary stupidity" but suggested Bailey Gwynne had shown "recklessness" in assaulting a fellow pupil.
To convict of murder, he added, the jury had to decide the accused had the state of mind to measure up to a deliberate killer.
He said: "This was a single blow".
Mr Duguid said a "trivial" matter started the fight, but said the accused was not a "fighting boy".
He said: "Of course if he did not have a knife that day there would be a burst nose and a fat lip but for who? Bailey Gwynne? I don't think so."
He said of the victim: "For his mother to be called fat was the spark to this terrible, tragic event."
Judge Lady Stacey said there may be feelings of "pity", "sympathy", "outrage" and "sheer sadness" but that the jury should look at the case calmly.
She directed the jury to convict the accused of two charges of having a knife and knuckleduster in school.
But she said the real question was charge three, whether the accused was guilty of murder or culpable homicide.
The trial has heard the accused stabbed Bailey in the school on 28 October last year and he died after his heart was punctured.
The murder charge against the 16-year-old claims he did "engage in fighting" with Bailey and struck him on the body with a knife.
In addition, the accused is also alleged to have had knives or "bladed instruments" as well as two knuckledusters at the school "without reasonable excuse or lawful authority" on various occasions between 1 August 2013 and the day of the alleged murder.