Minnie Simpson, 73, told the High Court in Glasgow yesterday she screamed for help as she comforted her dying husband James Simpson, 76, in the street.
Mrs Simpson was giving evidence at the trial of Christopher Grenfell, 25, who is accused of taking Mr Simpson's Land Rover Discovery from outside his home and leaving the retired lorry driver so seriously injured he died. Grenfell denies murder.
The jury heard how Mr and Mrs Simpson had been watching TV in Ashgill, South Lanarkshire, on November 29 last year when they heard the sound of glass being smashed.
Mrs Simpson told the trial: "My husband immediately got up – he was a very fast mover – and he shouted: 'They are stealing the car'.
"He was down the stairs in about a second flat."
She said Mr Simpson vaulted through the gap in the front door where the glass had been.
He then ran to his car and opened the driver's door to try to prevent it being stolen.
Mrs Simpson recalled shouting at her husband to "come back and leave it".
She added: "A great relief went through me when I saw the car going up the road. I was then very astonished when the car stopped suddenly and I went into despair when it reversed back to where it had been."
The pensioner said she remembered her husband was "whirled around and around".
Mrs Simpson said: "I shouted 'stop', but no-one was listening."
The court heard the Land Rover "went like a bullet" away from the scene before Mrs Simpson went to her husband's aid.
He was "half on the pavement and half on the road" near to his home.
The witness told the jury: "I said: 'You will be alright, Jimmy', but he was not looking at me. He was just staring. I was shouting: 'Help me somebody, help'. My neighbour, who is a doctor, came out and took his pulse. I was there screaming and screaming."
Grenfell's QC, Ian Duguid, later challenged Mrs Simpson's account of what happened that night. But Mrs Simpson said: "I will never forget it as long as I live. It flashes before my eyes and I cannot get to sleep because of it."
Mr Duguid said Mrs Simpson's memory could be "blurred".
The witness replied: "Not a chance."
Mr Simpson's neighbour, retired GP Dr Donald Hopkins, 76, ran out to help after hearing a bump and a woman scream.
He said there was a body lying on the road and even though it was his neighbour he didn't recognise him.
Dr Hopkins said the man's face was covered in blood and he tried to keep his airways open.
He added: "His pulse was steadily getting weaker and weaker and he was breathing less. And I thought I was going to lose him. About two or three minutes before the police arrived, he died."
He said at first he thought the man had been attacked, due to the state he was in.
He described Mrs Simpson as "frantic and at times hysterical".
Dr Hopkins said he didn't recognise Mrs Simpson either and added: "She is normally a well-groomed quiet person and this was a woman who was dishevelled and screaming."
Grenfell is joined in the dock by co-accused William MacVicar, 24. MacVicar, who is not charged with murder, is accused of acting with Grenfell and others to conspire to carry out car thefts.
The trial, before judge Lord Burns, continues.