A 10-month-old baby died after his nanny "dangerously and excessively" shook him, the Old Bailey has heard.
Joshua Paul was being looked after by Viktoria Tautz at his home in Haringey, north London, on 29 August 2014.
Almost 30 minutes after his mother left for work, he collapsed and was taken to hospital. He died on 1 September after being moved to Great Ormond Street.
Ms Tautz, 34, of Holly Park Road, Barnet, denies one charge of manslaughter.
Jurors were told Joshua died "because of a head injury that caused bleeding in his brain, eyes and other spinal injuries".
At the start of Ms Tautz's trial on Monday, prosecutor Zoe Johnson QC added: "On that day, for whatever reason... something snapped in the defendant and for a short while she lost her temper with Joshua and assaulted him, causing all those injuries.
"Her account of what happened whilst she was looking after Joshua does not explain Joshua's various injuries and therefore something else occurred - we suggest a dangerous and excessive shaking of Joshua - which the defendant has not revealed."
Ms Tautz was arrested on 5 September and in police interviews said she had played a horse-riding game with Joshua. She said he had not had any accidents and she denied shaking him.
When paramedics arrived at the flat at 09:11, she told them the boy had been crying in his cot, and that he "shook twice" when she picked him up, before he went floppy and stopped breathing.
Doctors at Great Ormond Street said Joshua had suffered "a devastating and irrecoverable brain injury", his brain was not showing signs of activity, and his heart could stop at any time.
In a statement read in court, Ms Paul said she paid Ms Tautz £3.60 an hour, her son was "happy with her", and that she "never saw her lose her temper".
The court heard that Joshua, who was born about 10 weeks early, had a large head for his age and was being monitored.
The trial continues.