A jury's been told the crown case against murder accused Hakyung Lee relies too heavily on potentials, to rule out Lee's insanity defense

The 45-year-old's on trial at the High Court at Auckland charged with murdering her two young children in 2018, and leaving them in suitcases.

Defence lawyer Lorrainne Smith says key parts of the evidence, like the time of death, can't be confirmed and leads to gap filling.

She says attempts to fill gaps are limited by the investigation beginning four years after the event, meaning the Crown has to piece together what happened.

However Smith warns against guess work.

Smith says purchases the Crown argues were made before the children's deaths, have multiple other possible explanations.