The Crown has told the High Court in Dunedin it is basing its case in a euthanasia trial of a forensics expert on early drafts of a book he wrote.
The trial began on Tuesday of Sean Davison, who is accused of attempting to kill his terminally ill mother Patricia Davison with morphine in 2006.
Professor Davison was born in New Zealand and now heads a DNA laboratory at a South African university which works on human rights cases.
He wrote about his experience of his mother's death in a book, entitled Before We Say Goodbye, published in 2009.
Crown prosecutor Robin Bates says he will present a large amount of circumstantial evidence, including early drafts of Professor Davison's book, in which he describes administering his mother with a lethal overdose of morphine.
He read an extract to the jury.
Mr Bates says the crown also has e-mails between Professor Davison and the book's publishers that show he did intend to kill her.
But the defence lawyer Roger Laybourn said the allegation he would attempt to murder his mother is strongly rejected.
He says Professor Davison's case is that he loved his mother and would never have done anything against his will, or harm her.
Mr Laybourn says the Crown will have to establish that the things Professor Davison wrote truly describe what happened.
Professor Davison has pleaded not guilty to the charge.
He has said he wants to stimulate debate about the need for voluntary euthanasia to be legal and has been supported by pro-euthanasia campaigners.
A number of police, medical professionals and journalists are expected to be called as witnesses thoughout the three-week trial.