A teenage father was jailed for 18 months today for killing his four-month-old son.

James Tuffs, now 21, Onehouse near Stowmarket was found guilty of manslaughter in July for the January 2004 incident at his home in Stowmarket, Suffolk.

But the judge dismissed prosecution claims that he may have killed his son Byron because the child had disturbed his video game playing.

His partner, Zoe O’Leary, now 18, had told the court earlier how she found Tuffs lying on the sofa with Byron’s leg sticking out from under him.

“James was lying on him. I started shaking and screaming at him to move. He got up and picked up Byron. I said, ‘Oh my God you’ve killed my baby’,” she told Norwich crown court.

The court was told that Byron was “grey and floppy” when he was found, and doctors confirmed that he had a fractured skull and two fractured ribs.

Tuffs would care for Byron and his twin brother Tyrese downstairs while Zoe looked after their daughter Aaliyah, now two, upstairs.

Tuffs told police that he must have suffocated Byron after falling asleep with him on the sofa, but prosecutor Oliver Sells QC said that medical examinations of the children revealed injuries that could not have been accidental.

“These serious and extensive injuries were caused by this defendant who must have operated a persistent regime of cruelty,” he said.

Tyrese was found sleeping on the floor with fractures to his skull, ribs, arm and legs.

Several weeks before Byron’s death Tuffs had told Ms O’Leary that Tyrese had stopped breathing and needed mouth-to-mouth resuscitation, but a health check-up found that he was well.

The jury of eight women and four men found Tuffs not guilty of cruelty to Tyrese but took two hours to find him guilty of the manslaughter of Byron.

The prosecution had linked these injuries to Tuffs’ obsession with his Nintendo GameCube computer game console.

Ms O’Leary said that he would allow the twins to fall asleep on the sofa while he played computer games and was excited about buying a new computer game called True Crimes shortly before Byron died.

He once had an outburst of swearing at her when she stepped in front of his view of the screen, the court was told.

“He would look after the twins downstairs in the room where the sofa was. After changing them he spent a lot of time watching television, playing computer games into the night,” said Mr Sells.

“You will hear something about his moods, irritable if his computer games were interrupted, on occasion shouting. He would rather play computer games than anything else.”

The family had regular visits from medical officers but neither of the children had external injuries and the extent of damage only emerged in X-ray examinations.