Neil Charles, 47, was stabbed in the chest in June 2021 in Bury St Edmunds, Suffolk. He had been seen earlier that evening attempting to open car doors.
Both David King, 55, and Edward King, 19, of Radnor Close, denied murder, with the father claiming that Mr Charles had run on to the knife.
They will be sentenced at a later date.
Ipswich Crown Court heard during the trial that David King was shown CCTV footage of Mr Charles on his driveway by his son and wanted to “stop and detain him.
Suffolk Police said they received a 999 call from David King around 3.55 a.m. on June 20th, stating that a man was attempting to steal from his car on the Moreton Hall estate.
King informed the call centre that he had attempted to apprehend the man who had fled.
He was unsure whether Mr Charles was injured or “acting,” but he may have been hurt when he ran at the knife he was holding.
Prosecutor Christopher Paxton QC stated during the trial that the two defendants were armed with a sword and dagger and desired “rough justice.”
Mr Charles was found seriously injured in Winsford Road by police, and he died two days later.
A post-mortem examination revealed that he died as a result of a single 12cm (5in) stab wound to the chest.
The dagger was used to inflict the fatal wound, and the sword caused a horizontal wound above Mr Charles’s left knee, according to police.
During the trial, both men denied intentionally killing Mr Charles, with David King claiming that he had disturbed Mr Charles while attempting to break into his car and that he had then run on to his knife.
Mr Paxton QC, on the other hand, claimed that the father and son had gone out to find and attack Mr Charles.
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