A London paramedic has been jailed for breaking his three-month-old son's arm in "an appalling act of violence".
But Gavin Gibbs, 41, was cleared of murdering his baby Charlie who died from a brain injury two days after being admitted to hospital.
The Old Bailey was told Gibbs whispered "please forgive me" as the child's life support machine was switched off in October 2008.
He claimed he was saying sorry for not saving the boy's life.
Sentencing him for causing grievous bodily harm, Judge Timothy Pontius told him: "Such an appalling act of violence by a powerfully-built man upon a helpless baby merely weeks old must be punished by an immediate prison sentence."
After the child died, it was discovered he had sustained a series of other injuries, including a fractured skull, a broken arm and a fractured rib from when he was two months old, and two more recent fractures - the result of pulling or twisting - to his left leg.
He had also suffered a fractured ankle shortly before his death. His twin sister had broken four ribs.
Jurors accepted Gibbs's claims that he had not hurt either child - except on 6 October when he broke Charlie's left arm.
Gibbs, of Brook Vale, Erith, south London, told the court that two days before Charlie's death, the baby had collapsed and he tried to resuscitate him.
Charlie had fallen off a sofa on an earlier occasion when Gibbs had gone to look for a camera to take a picture of him, he said.
Defence experts also said there may have been a medical reason for Charlie's brain injury.
Defending Gibbs, Judy Khan QC, described him as a "loving father" but the court heard that his stressful job led him to "deliberately and seriously hurt" the child.