A man has been jailed for a second time for an attack on a man who later died from his injuries.
Michael Newson, 23, was jailed for three years for causing Peter Collins, 56, grievous bodily harm following an attack in Milton Keynes in July 2008.
Mr Collins died in October 2009 having never left hospital.
Newson, who was released half-way through his original sentence, pleaded guilty to manslaughter at Luton Crown Court and was jailed for 18 months.
Prosecutor Benjamin Gumpert told the court that Newson, then aged 20, had been drinking heavily and there had been an incident in a bar in which he was spoken to by police and warned to go home.
Mr Collins was walking home through Lloyds Court when Newson appeared to have confused him with an adversary, the court heard.
Mr Gumpert told the court: "He ran after him and punched him hard in the back of the head causing him to fall and strike his head on the ground. An eye witness' impression was that the blow knocked him out and he was unconscious before he hit the ground. He was pole axed.
"The victim's skull was shattered and his brain severely damaged. He never recovered consciousness or left hospital. He died in October last year as a result of the head injury."
Barbara Humphreys, 60, Peter's elder sister, said: "This protracted living death must have been horrendous for Peter.
"Sometime we thought he did respond to our presence but we never knew if his response was intentional or instinctive. We did not know whether the facial grimaces and contortions and clumsy body movements were voluntary or otherwise. There were times when he cried.
"Invariably I cried all the way home and each visit would be followed by days of emotional turmoil."
Newson, from Hudson Lane, Milton Keynes, is due to be released next August.