Ashley Palmer was originally charged with Grievous Bodily Harm (GBH) after leaving a 38-year-old Bernard Farrell, of Birmingham, in a critical condition following an attack on November 3 last year.
But 10 days later, Mr Farrell died of his injuries and Palmer’s charge was changed to murder shortly afterwards.
A trial opened at Northampton Crown Court last week, and this morning the jury of seven women and five men found Palmer, of Moss Walk, Corby, guilty in a unanimous verdict.
He will be sentenced at Birmingham Crown Court, “in due course,” according to judge Rupert Mayo, who said he wanted to give probation officers time to draw up reports on the defendant.
The judge told the court: “There is only one sentence I can pass and it will have to be a life sentence.
“But before passing this a judge has to hear more information and has to set a minimum tariff for which he is eligible for parole.
“He will remain on licence for the rest of his life either way, which is why it is a life sentence.”
Palmer, who appeared at court in a light blue shirt with short dark hair, showed little emotion as the verdict was returned.
Thanking the jurors for their efforts, Judge Mayo said they had been forced to study a “harrowing piece of CCTV” taken outside the Oakley Road KFC on the night of the assault.