The Crown says a Hastings man became angry and frustrated while playing a video game console and fatally assaulted a five-month-old boy.
Trent Owen Hapuku, 22, is charged with the manslaughter of Mikara Reti in the Hastings suburb of Flaxmere on 11 January this year.
Crown prosecutor Steve Manning told the Napier High Court the accused spent most of that day at the home of the baby's mother using a Playstation.
Mr Manning said sometime in the early evening, Mr Hapuku deliberately assaulted the baby. The injury was so severe the boy's liver burst and several ribs were fractured and he died within an hour.
Mr Manning says the court will hear evidence that during the time the injuries had to have been inflicted, the accused was the sole person in charge of the baby.