Sean Davison Convicted of Procuring Mother's Death

In New Zealand, Sean Davison has pleaded guilty to a charge of procuring and inciting his mother's death.  He gave his cancer-ridden mother, Pat, a drink containing crushed morphine tablets before she died.  

What is odd, however, is that Pat had earlier tried to starve to death.  But she was still alive after 32 days.  Since Pat was a medical doctor and Sean a microbiologist, it is unclear why Pat tried a hunger strike (with water) as opposed to a refusal of both food and fluid.  That would have been far quicker.  It would have been more peaceful.  And, in contrast, to ingesting lethal medication, it would have been legal.