After his mother's death, Davison returned to his job as a forensic science lecturer at the University of the Western Cape in South Africa. There, he drew on diary notes to write a book, Before We Say Goodbye. Parts of the original manuscript for that book were edited out and neither Davison nor publisher Christine Cole Catley would say what had been removed.
But a few weeks later, the leaked manuscript left no doubt about Davison's hand in his mother's death: it said she died hours after he gave her "a lethal drink of crushed morphine tablets" dissolved in water.
"I held it in front of her and said: 'If you drink this you will die'," he wrote. "I really wanted to be so absolutely sure that there was no hesitation.
"She answered: 'You're a wonderful son'."
The manuscript also shows that Davison was clear about his intentions. He wrote: "To kill is to kill, no matter how sweet and right it is. I am committing a premeditated killing."
If Davison, 50, had not started keeping a diary, had not decided to write a book after one sister recommended he share the experience, had not decided to promote the book by sending copies of the manuscript to various publishers, but had simply returned to South Africa after Pat Davison died, the world would have been none the wiser.
Cole Catley, who died this year at 86, was the only publisher prepared to take on Davison's book. She sat in on my interview with Davison in her lounge overlooking Waitemata Harbour - and it was Cole Catley who stepped in when I asked him about the foreword to the book which said parts of the original manuscript had been edited out "for legal reasons".
I asked him how much was edited out. Last week in court, I was asked to recall his reply: "There were aspects edited that ran the risk of prosecution," he said. "I said 'legal reasons' in the foreword ... It's not hidden and I was pleased the publisher allowed that foreword to go in because an author wants to tell a story and if it's a true story they want to tell it word-for-word."
Now, what of Davison and his future? Justice Christine French asked for a pre-sentence report on home detention, so he will probably have to serve a custodial sentence before returning to his partner Raine Pan and their two small sons Flynne and Finnian in South Africa. Davison missed hearing Finnian's first words because he was awaiting a court hearing; now he may miss many more milestones. "One day the boys will feel very proud about what he's done," Pan told the Cape Times this week. "They will understand what Sean did is because of the love for his mother."
Davison told me he decided to keep a diary to help him keep his own sanity in a "totally out of control" situation. The decision to publish that private diary was made because he felt it would stimulate debate about voluntary euthanasia - something he has certainly achieved.
Curiously, while Davison has talked publicly about his mother's death, he was unable to speak openly to his mother about it. Even though they spent day after day together knowing she would die, he told me, they hadn't even discussed her funeral. "My mother was a very conservative woman, a very dignified woman," Davison said. "Looking back now, I think ... she would have liked to talk about it.
"It was me - I hadn't learned to open up about it and now I have because of this experience ... she was sparing me by not talking about it."
