A distraught wife went to the police station for help when her husband came home covered in blood, a jury heard.
Carol Rudwick feared her husband, Brian, had been involved in a fight with her ex-husband, Bill Davey.
But police already knew Mr Davey had been found dying in the road outside his home in Nuthurst Place, Whitehawk, Brighton.
Rudwick, 34, of Tarner Road, Brighton, a former jailer at the city's magistrates court, has denied a charge of murder.
He is accused of stabbing Mr Davey with a combat knife and slicing his throat from side to side on the night of February 15.
Lewes Crown Court heard there had been a history of ill feeling between the two men before the attack, which happened while Mr Davey was walking his dog.
Mrs Rudwick arrived at the police station in a distressed state.
PC Emma Wigglesworth said: "She was emotional, very upset and crying."
The officer said Mrs Rudwick believed her husband had been involved in a fight with her ex-husband.
Detective Constable Jason Feltham said he went to Rudwick's home to arrest him for murder.
Rudwick told the officer he did not know where the knife was as he had thrown it away as he walked home from Whitehawk.
He said he had changed his clothes and the ones he had been wearing were then in the washing machine, which had been switched on.
The jury heard Rudwick told police following his arrest he was suffering from post-traumatic stress disorder and could not remember anything that had happened.
Mr Davey, an electrician, had been due to stand trial at crown court on charges of sexual assault, which he denied. But he died 12 days beforehand.
The trial continues.
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