His mother commenced a water-only diet shortly after. She wanted to die and had asked several people, including Davison, to help her.
A few months later, Davison crushed up what he believed would be a lethal number of morphine tablets in a glass of water.
As no post mortem was ever carried out it is not possible to say whether she died from the overdose or not.
The offending only became known after a draft copy of a manuscript he had written for a book was sent to a journalist, which someone sent to Auckland police.
In 2011, Davison pleaded guilty to and was convicted in the High Court at Dunedin of counselling and procuring his mother to commit suicide and sentenced to five months' home detention.
The Medical Sciences Council was aware of this conviction at the time it granted Davison's application for registration in 2018.
But they were not aware of his other offences.
Davidson founded Dignity SA, a group that supports and advocates for law change in the right to assisted suicide in South Africa.
In 2013, he assisted Dr Anrich Burger, a medical doctor and quadriplegic, in suicide, by administering a lethal concoction of drugs.
In 2015, Davidson also assisted Justin Varian, a man who had a diagnosis of motor neurone disease, by placing a bag over his head to use helium deoxygenation.
Also in 2015, he helped Richard Holland, a man who had suffered brain injuries and had no motor function, by administering a lethal dose of fluid containing pentobarbital.
Davison wished to return to New Zealand to work and indicated that on his application form to the MSC.
In response to the question "do you have any criminal convictions, or do you have any criminal charges pending?", he replied that he was convicted of the assisted suicide of his mother but did not mention the other charges.
A further internet search by the MSC revealed Davison's offences in South Africa and he was asked to provide evidence of any rehabilitative steps taken since these matters.
In his response, Davison did not disclose that he had been involved in assisting with the deaths of Burger, Varian or Holland.
In June 2018, the council voted by a majority to register him.
Months later he was arrested in South Africa and charged with the murder of Burger, Varian and Holland.
He pleaded guilty and was convicted in the High Court of South Africa and sentenced to three years' correctional supervision.
The council has decided to censure Davidson as well as cancel his registration immediately and order him to pay $5604 to the Professional Conduct Committee and $2835 to the tribunal.
