A seven-week-old baby died after being bitten on the nose and violently shaken or swung by his teenage father, a court has heard.
The infant suffered fractures to his skull, leg and ribs at a flat in Southampton in February.
The 17-year-old, who cannot be named for legal reasons, denies murder.
The baby's 19-year-old mother denies a charge of cruelty to her son, by failing to protect him from the attack and by failing to summon help quickly.
The trial at Winchester Crown Court was told the baby died in hospital about two hours after the alleged attack.
Adam Feest QC, prosecuting, said neighbours heard "blood-curdling or painful screaming" in the early hours of 11 February.
The boy "met a violent end as a result of an assault or assaults in the flat" some time before 03:45 GMT, Mr Feest said.
The barrister said the cause of death was a "blunt trauma impact to the back of the head" causing an "extensive complex fracture".
The baby also had a spiral fracture of the left leg, which would have caused "indescribable distress and pain".
Mr Feest told the jury the injuries suggested the child had been "swung by the legs with his head striking a firm surface".
The father had previously inflicted further injuries including fractures to the ribs, leg and collarbone in the days leading up to the baby's death, the prosecutor said.
Mr Feest told the court that police found a bloodstained baby grow tucked into the arm of a sofa in the flat, as well as bloodstained baby wipes in the bin. The prosecutor said this was an attempt to clean the baby after his nose was bitten.
At about 04:30, the mother called a downstairs neighbour for help.
By that stage, the baby's skull was clearly showing the shape of an injury, the court was told.
The mother told the neighbour she had not called an ambulance because she did not want to lose her partner or her son, Mr Feest said.
Paramedics arrived shortly afterwards and gave the infant CPR and an electric shock to restart his heart, but the injuries were "almost certainly non-survivable", the prosecutor said.
The jury heard the father told a neighbour, "What have I done?", as they waited for news of the baby's condition from the hospital.
The teenager later told police the baby had accidentally fallen on to the floor, the court heard.
Mr Feest said the bite mark on the infant's nose was consistent with the father's dental pattern.
He said the teenager's partner at the time either saw the attack on the child or "must have been aware very shortly afterwards" but failed to raise the alarm.
The trial continues.