In the first criminal investigation of euthanasia since Belgium legalized the practice, the country's authorities are looking into the 2010 death of a woman with Asperger syndrome whom prosecutors say may have been illegally poisoned.

Thirty-eight year old Tine Nys was reportedly diagnosed with Asperger syndrome, a mild autism spectrum disorder, two months before being legally euthanized. Asperger syndrome is one of the most common mental health conditions leading to euthanasia in Belgium, along with depression and personality disorders, the Associated Press reports.

Euthanization of adults was legalized in Belgium in 2002, and of minors in 2014.

The country's euthanasia commission had previously dismissed Nys' family's complaint.

The deceased woman's sister told the Associated Press that though Nys suffered from mental health issues, it was "unthinkable that those problems warranted her death." She also alleges that the doctors fumbled Nys' euthanasia procedure, and that Nys was so desperate to die that she "manipulated the test" administered to her to ensure she was diagnosed with incurable Asperger syndrome.

After Nys' family filed a criminal complaint, her doctors attempted to block the investigation. The psychiatrist who approved Nys' request to die, Dr. Lieve Thienpont, reportedly wrote that Nys' family was a "seriously dysfunctional, wounded, traumatized family with very little empathy and respect for others."

The doctors who approved Nys' euthanasia, including Thienpont, will now face trial for poisoning, according to a prosecutor for the case. A conviction in the case could carry a lifetime prison sentence.

Joe Zalot, a staff ethicist at the National Catholic Bioethics Center in Philadelphia, said Catholic teaching holds that both euthanasia and assisted suicide are impermissible.

"Both are immoral, but I would say euthanasia has a much greater gravity many cases, you're killing the patient without the patient's consent, even; the patient doesn't even know what's going on," Zalot told CNA.

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"There are other cases of families of people who were euthanized, both in Belgium and the Netherlands, who are raising some very serious questions about what doctors are doing, after their loved ones were killed without them even knowing about it," he said.

Teaching in his 1995 encyclical Evangelium Vitae, St. John Paul II wrote that "euthanasia is a grave violation of the law of God, since it is the deliberate and morally unacceptable killing of a human person. This doctrine is based upon the natural law and upon the written word of God, is transmitted by the Church's Tradition and taught by the ordinary and universal Magisterium."

Zalot said: "Euthanasia is akin to murder. You are taking someone's life, and from the Catholic Church's perspective no one should have the ability, let alone the right, to take another person's life,"

"The mercy [killing] arguments you'll hear…'We're doing this to alleviate someone's pain' most cases pain can be alleviated without resorting to [euthanasia]."

"Belgian doctors are essentially taking it upon themselves the determination of a person's 'quality of life,'" Zalot said. "'Quality of life' has essentially become a buzzword to support euthanasia or assisted suicide."

In the United States, seven states and District of Columbia allow assisted suicide, where the doctor provides the patient with a means to kill themselves.

"If you look at the progression of it, you look at what has happened in Belgium, in Switzerland, and in Canada...That is coming to the United States," Zalot said.

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"And it's going to come through the states that have already legalized assisted suicide...I would guess in the next five or so years."

Belgium's law allows minors of any age who are terminally ill to request euthanasia. Parental consent, as well as the agreement of doctors and psychiatrists, is required.

In 2016 and 2017, three minors availed themselves of the procedure and were euthanized, according to a government report.

There were 2,028 euthanasia deaths in 2016, and 2,309 in 2017, a 13 percent rise year-on-year. The report found that cancer is the primary reason individuals seek euthanasia.

"It's the slippery slope at work," Zalot said. "You have an untreatable, terminal physical disease, and that's where the advocates [of assisted suicide and euthanasia] always start...People say it's going to be limited to instances of terminal illness. Well, it's not."