A young motorist gestured at the driver of a car he had been tailgating moments before crashing and fatally injuring a pensioner, a court was told.
Alison Bedwell, who was in her 60s, was cut free from the wreckage but died in hospital almost three weeks later.
Christopher Tinkler, 20, denies causing her death by dangerous driving.
He wept into a handkerchief in the dock while the jury at Lewes Crown Court was told how the crash took place on the A26 near Eridge on June 12 last year.
Mrs Bedwell, whose husband was in the passenger seat of their Austin Metro, had been driving to their home in Crowborough after spending the morning shopping.
Anthony Niblett, prosecuting, said Tinkler, of Sheepstreet Lane, Etchingham, near Robertsbridge, was responsible for a prolonged piece of dangerous driving over about 1.5 miles before the collision.
Witnesses had seen Tinkler tailgating a Mazda as he drove north at speed with his girlfriend in the front passenger seat.
When the Mazda overtook a lorry, Tinkler followed and then tried to overtake the Mazda.
As he passed the Mazda in his Peugeot 306 he gave the driver "the finger" and deliberately swerved to cut him up.
But Tinkler lost control and swerved across the road directly into the path of oncoming traffic.
Mr Niblett said before the crash Mr Bedwell, who was also injured, only had time to shout out to his wife to look out.
There was nothing she could do to avoid the collision and there was, as her husband described, an almighty impact.
Another driver, who was unable to avoid crashing into the wreckage, had minor injuries.
Mr Niblett said: "As the defendant passed the Mazda he leaned across his passenger and raised his finger in the well-known insulting one-finger gesture to the occupants of the Mazda car he had been following so closely.
"His car spun out of control and rotated into the path of the Metro with tragic consequences."
The court heard Tinkler, 19 at the time, needed hospital treatment after the crash.
The trial continues.
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