Meth gran murdered toddler 'because he was too hard to toilet train'

Kathleen Elizabeth Cooper, 65, stands in the dock at the Auckland High Court while facing a murder charge over the death of her grandson.

An Auckland toddler was murdered by his grandma because he was too hard to toilet train and she was irritable from smoking methamphetamine, prosecutors say.

Kathleen Elizabeth Cooper, 65, is standing trial in the High Court accused of murder by throwing her grandson down the hallway of their Manurewa home after a toileting accident on December 13, 2015.

Suffering serious head injuries, two-year-old Jermain Mason Ngawhau was rushed to Starship Hospital for emergency surgery, but died five days later.

Closing the Crown case on Friday, prosecutor Aaron Perkins QC said Cooper had volunteered to care for her troubled daughter's four children, all aged under 5, but gradually became overwhelmed by the challenge.

She took to regularly hitting them, with Jermain - whose delayed development made him slow to walk and learn to use the toilet - found to be covered in numerous old and fresh bruises, he said.

To make matters worse, Cooper was a meth user, Perkins said. Cooper's worsening frame of mind "placed Jermain in the greatest of danger" until the situation erupted on December 13, he said.

It was then Cooper murdered the tiny toddler by throwing him in a way she knew could kill him, Perkins said.

Cooper's lawyer Paul Dacre QC admits she killed Jermain, but argues she did not intend to kill him and so shouldn't be convicted of murder.

However, Perkins said Cooper was aware of the dangers of throwing Jermain because she had whacked her grandkids so often, she knew what did and did not hurt them.

He reminded the jury of how one of the children had been seen with a black eye and that Cooper gave three different explanations for its cause to three different people.

Another witness also told how, one day before Jermain died, she saw Cooper yelling and swearing at him as she dragged him by the arm, naked and screaming, from the toilet to his bedroom.

Perkins argued Cooper would have been irritable on the day she killed Jermain, because she was coming down from smoking meth and getting little sleep in the process.

This was backed by Cooper's nephew, who told the court he smoked meth with Cooper and by medical tests showing her grandkids had also been exposed to the drug, Perkins said.

Tragically, with Cooper in a foul mood and tension building, December 13 "was quite the wrong time for Jermain to have a toileting accident", Perkins concluded.

Dacre is expected to close the defence case on Friday afternoon.

- NZN