A man killed his step-daughter with a blow to the stomach, a jury was told yesterday.

Demis Peter Paul, 25, went on trial in the High Court in Palmerston North on a charge of murdering 14-month-old Mereana Clements-Matete on December 22 last year.

The court was told that Paul admitted punching Mereana but denied intending to kill her.

"Demis Paul acknowledges that he got angry and he struck this little girl and, clearly, he struck her very hard," his lawyer Duncan Harvey told the jury.

Paul would argue that he did not intend his blow to kill the infant.

But the Crown contends Paul knew exactly what he was doing when he struck the child.

"He punched the 14-month-old in the stomach with all of his force... knowing that he would cause bodily injury to Mereana that would be likely to cause death, and despite that knowledge, he did it," Crown prosecutor Fiona Guy Kidd said.

Paul had been babysitting Mereana, her brother Jade, six, and cousin Caleb, two, on the evening of December 22 last year at his partner Kim Matete's home while she was out Christmas shopping.

Paul became angry with Mereana, who was screaming and had to be put to bed.

He told police that he became exasperated with the child and punched her in the stomach as she lay on her side in bed.

He told police the punch he inflicted was "quite severe" and admitted he often didn't know his own strength.

Ms Guy Kidd said medical evidence due to be revealed in court later this week would show the blow inflicted by Paul moved upward and across Mereana's body, effectively "guillotining" the infant's small bowel and mesentery against her spine.

Witnesses would tell the court Paul originally tried to blame Mereana's death on her cousin Caleb, who, he said, had been jumping on the girl.

A total of 27 prosecution witnesses are expected to be called.

The trial is expected to run in to next week.

- nzpa