A 15-year-old youth was given a life sentence for stabbing a student to death in a row over conkers.
Architecture student Steven Grisales, 21, died in August last year, after he challenged youths who were throwing conkers in their spiky husks at him.
He had been shopping for his grandmother and was on his way to Silver Street station in Edmonton, north London, when he was attacked in College Close.
The youth, who cannot be identified for legal reasons, denied being the killer but was found guilty of murder at the Old Bailey last month.
Judge Richard Marks ordered that the youth be detained at Her Majesty's Pleasure with a minimum term of 10.5 years.
Judge Marks said Mr Grisales was "an outstanding human being in many ways".
The defendant had been in court for robbery and burglary and was subject to electronic tag monitoring as part of a rehabilitation order imposed the previous month.
The prosecution told the Old Bailey that the youth had removed the tag two days before but the incident happened before his 9pm curfew.
Judge Marks said his pre-sentence report made "grim reading" and mentioned two incidents with knives, one at school and the other involving his mother.
Andrew Edis QC, prosecuting, told the trial: "This was a sudden, unnecessary killing as a response to a confrontation which took place in the street, which was about nothing very much.
"It was about throwing some conkers. Horse chestnut trees in north London shedding their conkers, people picking them up and throwing them about."
After the verdict, Detective Inspector Richard Beadle said: "Steven did no more than stand up to unruly youths and for that he has lost his life.
"The defendant's arrogance and contempt for others belies his age."
Mr Grisales' mother, Jasmid, of Enfield, north London, said in a statement: "Steven was always loved by every person who had the privilege of knowing him.
"He always gave without expecting anything in return and he always tried for everyone around him to be happy.
"This result can show that in a way it is justice and people should start learning that for every wrong you do, sooner or later you have to pay the price."
Mr Grisales had returned to Britain from Argentina to take up a scholarship to study architecture at Westminster university.
His organ donations following his death helped to save the lives of three women.