A father has been jailed for three years for the manslaughter of his son who he shook as a baby, leading to the child’s death almost 15 years later.

Jack Doak Mitchell was four months old when his then 18-year-old father John Doak shook him and caused him serious injuries on May 22 2001 in Laindon in Essex.

A judge said that only the defendant knows exactly what happened, as he was alone with the child when the incident happened.

But David Emanuel, mitigating at Chelmsford Crown Court, said that according to an expert report “what probably happened was the loss of control temporarily while trying to stop him crying”.

Jack suffered severe brain damage, required 24-hour care, was blind and unable to talk, had limited ability to move and had a “very poor… if non-existent” quality of life as a result of the assault, judge Mr Justice Cavanagh said on Monday.

Jack died aged 15 on March 13 2016 after developing respiratory symptoms linked to the consequences of his injuries.

He had been looked after by foster carers since.

The judge told Doak, who is now aged 37: “The cause of his death was a shaking-type assault that you inflicted on Jack many years previously, on May 22 2001, when he was only four months old.

“In the intervening period, Jack suffered from brain damage and from other very serious health problems that were the direct result of your assault on him.”

He said he had seen photographs of Jack and he was a “lovely little boy”. He added: “Tragically, he did not have sufficient time for his personality to develop before the assault that led to his severe disabilities.”

The judge said that the degree of force used “is not known, but that it would be likely to be viewed as being an obviously inappropriate way of handling a baby if seen by an independent witness”.

He told Doak: “Only you know exactly what form the assault on Jack took on May 22 2001, or how severely you shook him, or why you did so.

“However I sentence you on the basis that you did not intend to kill him or to cause him really serious harm.”

The defendant, of Delgate Avenue, Spalding, Lincolnshire, admitted to Jack’s manslaughter.

He had previously been convicted at Basildon Crown Court in 2002 of inflicting grievous bodily harm upon Jack with intent.

In 2002, he was sentenced to four years in a young offender institution and served two years and eight months in custody.

The judge said he took this previous sentence into account when sentencing him for manslaughter “as it arises from the same incident”.

Mr Emanuel, mitigating, said that unemployed lorry driver Doak is married with three children and three step-children.

He said Doak “grieves for (Jack) every day” and is otherwise of good character.

Doak was jailed for three years and as he was led to the cells he shouted “wait til the truth comes out” and “love you” towards the public gallery as several family members wept.