Susan Austen's lawyer took just 40 minutes, and a statement from one witness, to present his client's defence in the High Court at Wellington.
Dr Donald Stevens, QC, had the registrar read the statement of clinical psychologist Professor Glynn Owens to the court on Wednesday.
Austen, 67, a Lower Hutt teacher, is accused of assisting Annemarie Treadwell to take her own life in 2016, along with two other counts of importing Class C controlled drug pentobarbital, on two occasions between 2012 and 2016.
Owens has spent more than 30 years studying, lecturing and writing about the psychology of death and dying, particularly looking at euthanasia.
His evidence, read out by the court registrar, said that merely possessing "end of life" drugs, such as pentobarbital, can actually ease suffering.
Only about 40 per cent of prescribed end of life drugs in Oregon and California, where they are legal, are actually used, he said.
"They can provide peace of mind and lessen pain and suffering," he said.
"The patient feels involved in choices being made towards the end of his or her life, to the extent that in some situations they have elongated patients' lives.
"Just having the drugs reduced anxiety and can focus someone on quality of life."
Stevens said the charge of assisting someone to commit suicide was rarely brought and difficult to prove.
"The prosecution must establish, beyond a reasonable doubt, that the intention to assist the commission of suicide was there," he said.
"Mrs Austen did not intend that Mrs Treadwell should commit suicide, but assisted her to obtain the pentobarbital. She intended that Mrs Treadwell should have control over her end of life issue - having that [drug] could have had a profound palliative effect to reduce suffering."
Stevens said the two importing charges would be addressed during his closing address.
"I will be making a detailed summary on the unsatisfactory evidence provided by the prosecution on these," he said.
He and Crown lawyer Kate Feltham will make their closing statements on Thursday, and Justice Susan Thomas will provide a summary on Friday, before the jury retires.