Two teenagers were branded cowards as they admitted killing a high-flying graduate in a "trivial" row over a discarded chocolate bar.
Evren Anil, 23, was punched in the face after remonstrating with the two youths after one of them threw a half-eaten Lion bar into his car.
He crashed to the ground "like a doll", his head bouncing off the pavement, and he died of severe head injuries eight days later, the Old Bailey heard.
Joanna Korner QC, prosecuting, said: "It was an argument over the most trivial of matters."
The victim's sister Elif Anil, 26, condemned the "vicious and callous attack" by "two heartless cowards".
Mr Anil had recently graduated with a first class honours degree in IT from Kingston University and had landed his "dream job" as a programme developer.
Miss Anil was driving him to a friend's house in her Peugeot 307 when he was attacked at traffic lights at Gipsy Hill, south east London in August last year when the older of the two youths threw a half-chewed Lion bar through the car's open window, and Mr Anil got out and threw it back at them.
Miss Anil urged him to get back into the car but he was punched in the face and fell to the ground so hard that his skull was fractured. He suffered a haemorrhage that moved his brain 16mm across his head.
A youth aged 17 from Tottenham, London, has admitted throwing the chocolate bar, and delivering the fatal blow to Mr Anil. The younger boy, aged 16 from Thornton Heath, London, threatened Mr Anil as well as a passer-by who tried to intervene.
Both have pleaded guilty to manslaughter and knife possession, and were remanded in custody to be sentenced on April 4.
