Shayal Upashna Sami was new to New Zealand, new to an arranged marriage, 18 and pregnant, and alone in a tiny flat for hours with a baby, but that did not make her "snap" and kill the child she was looking after, her defence lawyer says.

Sami, 21, is on trial in the High Court at Christchurch for the alleged murder of toddler Aaliyah Ashlyn Chand, who received fatal head injuries on January 6, 2015, while Sami was babysitting.

The defence claims the toddler sustained fatal injuries after falling off the couch, while Sami was in the kitchen cooking dinner.

Sami's defence lawyer Jonathan Eaton QC, told a jury on Thursday that it was "culturally insensitive" for the Crown to argue that because Sami, a Fijian- Indian woman, was in an arranged marriage and does not leave the house alone due to cultural reasons, it caused pressures on her.

"Where is the evidence that she was a woman at home that had so many pressures she was about to snap?" Mr Eaton said.

He continued to argue that the case relied solely on medical opinion, people who were not there and could not know what had happened.

The one-year-old suffered two skull fractures and bruising to her face, she was unresponsive when Sami picked her up and took her to the hospital, with the help of a neighbour.

Aaliyah died in hospital the next day.

Earlier, Crown lawyer Deirdre Elsmore argued that whatever happened to Aaliyah, was "borne out of frustration and stress".

"The defendant slammed (Aaliyah's) head on a hard surface in a moment of rage, which lead to her death," Ms Elsmore said.