UPDATED 12.16pm: The Christchurch labourer who allegedly inflicted serious head injuries on his five-year-old step-son had previously written about his grief online.

James Roberts has appeared in the Christchurch District Court this morning, charged with the murder of Leon Jayet-Cole.

Roberts, who recently married Leon's mother Emma, lived in the Papanui home where Leon was taken to hospital from last Wednesday.

The 34-year-old wrote on Facebook before his arrest that he was confused and broken, and felt like he had been robbed, calling Leon his superman.

He's been remanded in custody until June 19.