A father has been jailed for seven years after admitting killing his disabled seven-month-old son.
Nathan Pick, 38, lashed out at James-Lee because he could not get him to stop screaming at their home in Chaddesden, Derbyshire.
The baby, who was born with a heart defect and had to be tube-fed, suffered brain injuries and died the next day in hospital as a result of the blow to the back of the head.
Pick was arrested on suspicion of murder and and charged, but originally claimed to police that James-Lee had begun to fit and hit his head in his swing chair.
But on Wednesday, a week before his trial was due to start, he admitted manslaughter at Nottingham Crown Court.
In mitigation, Shaun Smith QC, defending Pick, said it had not been a deliberate act to kill or cause serious injury to the child. Mr Smith said: "He was frustrated by his inability to be accepted by his baby son. He is truly sorry for this. He would not want this to happen to anybody else."
The court heard James-Lee spent three months in hospital after being born with a heart defect in October 2011. His mother Hannah Goldby, who was Pick's partner at the time, called James-Lee "her little fighter". He required medication and care each day, the court heard.
Pick struggled to bond with his son and grew frustrated that he could not calm the child.
On May 7 last year, Pick "snapped" and lashed out at his son while the child was sat in his swing chair. He called Ms Goldby, who had gone to the fish shop, and said: "Come back quick. He's fitting. I think he's dead," then called 999.
Sentencing Pick, Mr Justice Julian Flaux said: "The stress caused you to snap. You did not intend to kill him or cause him serious injuries but you now accept that blow was an unlawful act."