A healthy 13-day-old baby boy was left with "catastrophic and irreversible" brain damage after being shaken by his father, a court has heard.
Daniel Sanzone is accused of deliberately inflicting what medical experts described as some of the most extreme brain injuries they had seen when he attacked Joshua Millinson at home in October 2015.
Sanzone, who denies murder, was alone in the lounge with the infant when the baby suffered a collapse.
Post-mortem examinations also revealed a catalogue of older fractures to the child's lower legs and rib cage, which doctors said were consistent with "twisting", "squeezing" and "being gripped forcibly".
Joshua's mother Zoe Howell, who is charged with causing or allowing the baby's death, told police her partner could "sometimes be a bit rough" with the child but said she had never seen him hurt the boy.
She later told officers: "I can't believe the dad has done it."
The pair are on trial at Birmingham Crown Court where on Friday a jury heard that it was the view of a host of medical experts that "Joshua sustained catastrophic and irreversible damage to the brain and brain stem" consistent with "shaking".
Opening the case for the Crown, Sally Howes QC told jurors: "It appears that there is little challenge to the medical, pathological and expert evidence that Joshua died as a result of deliberately inflicted injuries, causing a catastrophic collapse on October 24 and his death on November 21.
"The main issue for you to resolve is not what happened to him, but who is responsible."
Throughout the hearing Howell sat weeping uncontrollably and clutching a teddy bear in her lap, while Sanzone had his head in his hands.
Jurors were told that Joshua was born on October 11 at 39 weeks, a "normal, healthy baby".
During a routine medical examination four days later, a doctor described the baby as "active and alert".
A community midwife who saw Joshua at home - where he lived with Sanzone, Howell and her mother Sharon Howell - on October 17, described him as "pink in colour with good muscle tone, and alert".
But two days later, the couple turned up with their child at Wolverhampton's New Cross Hospital's accident and emergency department reporting that Joshua had a rash on his forehead.
He was examined by a nurse and doctor who diagnosed a milk or heat rash, but found the baby was otherwise normal.
Ms Howes said: "The doctor noted he didn't cry when his limbs were moved in order to remove his clothes."
But against the advice of the medics, Howell then self-discharged her child "as she was adamant she wanted to take him home".
The prosecution said a bone specialist who examined Joshua after his death concluded the leg and rib fractures may have happened before that hospital visit.
Three days later, the couple again brought Joshua to the hospital's emergency department with 23-year-old Sanzone complaining a midwife had caused his son's left leg to swell up after taking a blood sample at their home in Whitburn Close, Pendeford, Wolverhampton.
Ms Howes said Sanzone told medical staff "he was going to sue".
When the baby was examined by doctors, they found "no bruising or deformities of the arms and legs" and the child was discharged to come back for a check-up the next day.
However, Ms Howes said, "they failed to attend that review with Joshua".
On the night of October 24, Howell and her mother were at home with Sanzone, who was alone in the living room with Joshua.
Howell later told the police she was in the kitchen when she heard a "thud" from the lounge, and the baby "started screaming more than he normally would".
Taking up the defendant's account, Ms Howes said: "She went to the living room where she saw Joshua on the settee and Daniel hovering over him as if he was going to change him.
"Joshua was screaming, flat on his back, and when she asked what the noise was, Daniel reported that 'I dropped the remote'.
"But she noticed it (the remote) was still in its usual place."
Sanzone picked up the baby but he was "floppy" and "lifeless".
Ms Howes said: "He (Joshua) was no longer screaming, he just stopped and was gasping for air."
Howell, 19, became "hysterical" as her mother Sharon Howell stepped in and started CPR, in a desperate bid to save the child.
Paramedics arrived within moments and described Joshua as "grey".
He was taken to hospital and transferred to Birmingham Children's Hospital, with Sanzone allegedly telling doctors: "If something f***ing happens now, there will be trouble - someone's getting sued."
At hospital, the gravity of Joshua's "profound" injuries were revealed with a scan showing his brain had been starved of blood and oxygen.
Ms Howes said: "Sedation was discontinued, but despite this, there was no purposeful movement by Joshua.
"His pupils became continually fixed and dilated - he was just staring.
"From this day until the day of his death on November 21, Joshua remained unresponsive."
Jurors heard the authorities successfully applied to the High Court for permission to withdraw life support after an objection from Howell, and baby Joshua passed away peacefully in his mother's arms.
After his arrest but before his son's death, Sanzone gave an account to police describing how Howell's mother - who desperately tried to revive the child - had rocked the baby after its collapse, with him telling her "you don't shake a baby".
But Ms Howes said: "It's the Crown's case it is Daniel Sanzone who was alone with Joshua at the time of this collapse.
"Joshua had been fine and suddenly he was not.
"It is Daniel Sanzone, say the Crown, who is responsible for the collapse because it was him who inflicted these fatal head injuries by some form of shaking."
The prosecutor added it was "absolutely inconceivable the mother of such a tiny baby would be unaware there was something happening to him when he was with Daniel Sanzone".
Sanzone - charged separately with murder - and Howell deny causing or allowing their son's death, and child cruelty between October 15 and 24 2015, and the trial continues.