Brian Penn was convicted following a trial of inflicting blunt force trauma on Kaleb Penn’s head and body by unknown means and compressing his body on November 1, 2017 at a property in Ayr.
The baby was left so severely injured that he died two days later at the Royal Hospital for Children in Glasgow.
Penn, a former soldier, was also found guilty of assaulting Kaleb to his severe injury and to the danger of his life on various occasions between October 13 and 31 that year at a property in Ayr and elsewhere.
The 30-year-old had lodged a defence of incrimination blaming the child’s mother for the death.
Lord Weir sentenced Penn to 12 years behind bars when he was sentenced at the High Court in Glasgow on Wednesday, appearing by video link from prison.
Lord Weir said Penn had inflicted wounds on a "vulnerable baby lost to his family forever".
The judge added: “When Kaleb was born, he could have expected without realising it the loving parental care and nurture so vital to such helpless infants.
“The jury were satisfied that you inflicted blunt force trauma injuries to his head and body to sufficient seriousness [that] fractures appeared on an X-ray.
“The physical assaults you carried out were the antithesis for the care Kaleb looked to you for and his life was tragically cut short.”
Penn was originally charged with murder and attempted murder but was found guilty of culpable homicide and assault following his trial at the High Court in Glasgow.