Dutch prosecutors said in a statement the doctor "had not acted carefully" and "overstepped a line" when she performed euthanasia. Officials first began probing the case in September, when they found the doctor had drugged the patient's coffee and then had family members hold her down while delivering the fatal injection.
The doctor said she was fulfilling the patient's earlier euthanasia request and that since the patient was not competent, nothing the woman said during her euthanasia procedure was relevant.
But Dutch prosecutors argued that the patient's written euthanasia request was "unclear and contradictory."
"In her living will, the woman wrote that she wanted to be euthanized 'whenever I think the time is right.' But after being asked several times in the nursing home whether she wanted to die, she said, 'Not just now, it's not so bad yet,'" according to an earlier report by one of the Netherlands' euthanasia review committees.
"Even if the patient had said at that moment: 'I don't want to die,' the physician would have continued," the committee wrote, citing the doctor's own testimony.
Prosecutors said on Friday that the doctor should have verified with the patient whether or not she still wanted to die and that "the fact that she had become demented does not alter this."
Johan Legemaate, a professor of health law at the University of Amsterdam, said: "The patient's declaration has to be clear enough to the situation so doctors know when euthanasia can be applied."
"But should this include a situation where doctors are drugging patients secretly? It's now for the court to decide whether this doctor acted within the required limits," he added.
Legemaate said that there were very few cases of euthanasia in patients with advanced dementia, but that the decision to prosecute the doctor in this case might provoke more caution among health professionals.
Rene Heman, chairman of the Dutch Doctors Federation, said he respected how open the doctor had been about the case.
"Criminal law is always the last possible resort after a report of euthanasia," he said, noting that euthanizing people with advanced dementia continued to be very controversial.
The Netherlands is one of five countries that allow doctors to kill patients at their request, and one of two, along with Belgium, that grant the procedure for people with mental illness. For those with late-stage dementia, euthanasia is still possible if the person made a written demand specifying the conditions under which they want to be killed and if other criteria are met, namely if the doctor agrees the patient is suffering unbearably with no prospect of improvement.
"If the Dutch had decided not to prosecute this case, that would send a message that if a patient is incompetent, doctors can essentially do whatever they want," said Scott Kim, an ethicist at the U.S. National Institutes of Health.
"A case like this should serve as a warning for other countries," he said. "The Dutch seem to be recognizing that certain practices are out of bounds."
Earlier this month, friends of Audrey Parker, a euthanasia advocate in Canada, which legalized the procedure in 2016, said she was forced to end her life "prematurely" because the law only allows patients who are mentally competent to be killed.
A pro-euthanasia organization said it would soon be launching a campaign to challenge the Canadian law so that people can be euthanized even when they lack capacity.
Dutch prosecutors are also examining two other criminal investigations into doctors who performed euthanasia in questionable circumstances; two other cases were recently dropped.
Cheng reported from London.
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