A man was stabbed 18 times in front of his 14-year-old son after a "heated argument" over blocking the aisle on a London-bound train in January, a UK court was told.
Lee Pomeroy, 51, was attacked by Darren Pencille, 36, five minutes after boarding the train at Guildford, Surrey, on January 4, the Old Bailey was told.
The defendant's girlfriend, 27-year-old Chelsea Mitchell, is also on trial and denies assisting the offender, the BBC reported.
Prosecutor Jacob Hallam told the court that Pomeroy was killed the day before his birthday.
He said the victim and his son boarded the train at London Road Station at 13:01 GMT and within five minutes, he had been stabbed by Pencille.
"That wound to the neck was the first of 18 wounds with a knife that Pencille inflicted on Pomeroy that day," he told jurors.
"A little over an hour after he boarded the train, and despite the best efforts of the emergency services who rushed to save his life, Pomeroy was dead."
The prosecutor told jurors the events surrounding the killing were captured on CCTV and witnessed by other passengers.
Pomeroy and his son had boarded the same carriage as Pencille and made their way down the aisle, the court heard.
Hallam suggested they may have been "blocking" Pencille's way and the defendant had said: "Ignorance is bliss."
"That prompted Pomeroy to respond and ask what it was he meant. An argument began between them. It was an argument that became heated and became heated pretty quickly."
The prosecutor told the court Pencille rushed from the scene and was picked up by his girl friend Mitchell. The trial continues.