When a little girl's mother was out shopping, her stepdad struck the child in the stomach with enough force to rupture an organ and cause a fatal infection, a court has been told.

The Crown today delivered its closing arguments in the murder trial of Michael Joseph Martin, 25, who denies killing two-year-old Leilani Mary-Jane at their Manurewa home in June 2012.

The defence says Martin is innocent and the child's mother Amy Lorigan must be responsible.

Crown prosecutor Christine Gordon, QC, said Martin struck Leilani, either by punching, stomping, kicking, kneeing or using an implement, on June 9, 2012, when Ms Lorigan had gone out shopping. The injury was no accident, she said.


Leilani, who weighed just 12 kg, got more unwell throughout the day and was pronounced dead before 6am the next morning.

Any suggestion she was off colour on the morning of June 9 was ``unreliable'' and Ms Lorigan had told the court she had fed Leilani and was going out to buy ingredients to make a cake for her. Surely she would not have done this if her daughter was ill, Ms Gordon said.

Martin was interviewed by police in the days after Leilani's death and jurors might think his answers were "contrived'' and his descriptions of the girl's death lacking emotion, she said.

Ms Gordon told the court Martin also put a gloss on his relationship with Ms Lorigan and didn't mention his plans to leave her, or his frustrations with Leilani.

The Crown didn't have to prove any premeditation on Martin's part, but the jury would have to be sure he knew what he was doing could kill, she said.

"Anyone inflicting force like that on the abdomen of a little child would have known that the bodily injury was likely to cause death.''

Ms Gordon said murder would involve an impulsive act that was straight away regretted. Martin's situation could be a "classic example'' of this, she said.

The defence would point the finger at Ms Lorigan, but Ms Gordon said she was a loving mother who was not responsible for Leilani's injury.

Martin has also pleaded not guilty to a charge of child neglect for failing to provide Leilani with medical assistance.

The defence will present its closing argument tomorrow, before Justice Graham Lang sums up the case for the jury.