UPDATED 1:46pm: A man who played violent video games while seriously injuring his five-week-old son has been sentenced to four years and five months jail.

Devon Bird appeared in the Napier District Court this morning after pleading guilty to ill-treating a child and causing grievous bodily harm with reckless disregard.

The 21 year old student caused the injuries including a large skull fracture, more than 20 other fractures all over his body and a lacerated spleen.

Judge Bridget Mackintosh told the computer science student he had an inability to understand the seriousness of his own actions.

She says it was at the upper end of the seriousness scale.