[Brittany Maynard holding the prescription medicine she used to end her life peacefully and painlessly in 2014]
Does assisted suicide violate Christian ethics? Swiss Catholic priest and renown theologian Hans Küng says no in his book Eternal Life?: Life After Death as a Medical, Philosophical, and Theological Problem. Küng argues that people have the right to die with human dignity, and so there are situations where doctor-assisted suicide is morally acceptable. Küng does not support all forms of euthanasia or assisted dying (i.e. "Mercy Killing") but he does support active-assisted dying (e. g. assisted suicide) for people suffering from a chronic debilitating disease so that they may choose to die with dignity instead of prolonging their lives artificially with medical treatments that only further degrade their qualify of life or endure unbearable pain.
Euthanasia: Three Forms of Assisted Dying
Küng explains there are three forms of euthanasia: 1.) pseudo-assisted dying, 2.) passive-assisted dying and 3.) active-assisted dying. Generally all people oppose pseudo-assisted dying such as the Nazi eugenic programs that forcibly destroyed people judged undesirable. And, generally all people support most forms of passive-assisted dying where a person receives hospice care consisting of drugs that relieve physical and psychological pains. Another form of passive-assisted dying that is generally accepted is when a person declines extraordinary medical treatment that would prolong their life but also cause great suffering (there are some exceptions where a person continues to prolong their life even through suffering for the sake of other persons who need them.) The most controversial (and least socially accepted) of the three forms of euthanasia is active-assisted dying that is sometimes known as "mercy killing" and happens when a person's life is intentionally shortened or abruptly ended similar to Romeo and Juliet, or recently when Slobodan Praljak killed himself in court by consuming poison.
On pseudo-assisted dying, Hans Küng says: "What has to be rejected is pseudo-assisted dying or pseudo euthanasia (euthanasia in the pejorative-improper sense). By this is meant the destruction of life allegedly "not worth prolonging" ordered by the state and carried out without the consent of the person concerned: that is, the deliberate killing of deformed people, mentally or physically sick people and also socially unproductive persons." 
On passive-assisted dying when lives are not shorted, Hans Küng says: "Generally accepted is also (genuine) assisted dying or euthanasia without shortening of life, where the doctor restricts himself to providing pain-killers or anaesthetics. This kind of assisted dying is legally safe, ethically justifiable and medically required. Since the person has a right to a "natural," truly human, humane death, it is part of this humane death that bodily sufferings should be reduced to what is bearable and that the human psyche should be supported by psychopharmalogical drugs in emotional coping with the last phase of life. This of course does not mean that psychopharmological drugs can replace the best nursing and friendly human attention. "
On passive-assisted dying when lives are shorted, Hans Küng says: "Generally accepted also is passive assisted dying or euthanasia with a shortening of life as an incidental effect ( = indirect assisted dying). Or—to be more exact—assisted dying by breaking off artificial prolongation of life. It was a principle also of classical moral theology that it was not necessary to use media extraordinaria, "extraordinary means," for the preservation of life. This is true both for the patient and for the doctor." 
Küng says in the past, all forms of active-assisted dying were opposed by theologians and the general population consider it unethical. Public opinion has changed in recently years in the specific case of assisted suicide (which is a subset of active-assisted dying), and the support for assisted suicide is rapidly growing in America (73% support ) and among Christians in America too (57% support ), but assisted suicide remains to be a controversial and polarizing issue that is strongly opposed by those who do not support it, and only a handful of states have legalized assisted suicide .
This active dying (active euthanasia), aiming directly at a shortening of life, "mercy killing" is a matter of dispute. Formerly a consensus prevailed in regard to the rejection of any form of active-assisted dying: hence in the majority of countries the killing of a person, even at the later's express wish, remains as before a criminal offense.
The fact cannot however be overlooked that today more and more people and even whole organizations (euthanasia societies) are asking for the legalization of "mercy killing," carried out voluntarily by a doctor prepared to do so. As distinct from the Nazi compulsory euthanasia, it is a question here of a completely voluntary euthanasia on the part of both patient and doctor, where the exact conditions—in the narrower or the wider sense—are laid down in a declaration of the person concerned, authenticated by a notary public. The person would be put to sleep either solely with an incurable disease leading to death; or with a nonfatal but serious and painful bodily complaint (for example, respiratory paralysis); or—finally—with serious and irreparable brain damage or brain disease.
The theological controversy is centered on the question of whether man has the right to dispose of his life even up to his death. It should be noted that for us the question arises here, not in regard to the healthy person, but to someone who is seriously ill and even doomed to die (moribond). That is to say, I am not talking here about the person who is suffering and often only for a time—simply from weariness of life, of a young person—for instance—whose first love affair has gone to pieces and who now despairs of life. No, we are talking about a person at the end of life, inescapably approaching his death, caused by an incurable disease. Can he dispose of his life? 
Active vs Passive Assisted Dying
Küng argues that assisted suicide is acceptable because it is in the fluid area between passive-assisted dying and active-assisted dying. He is not in favor of all forms of active-assisted dying (i.e. "mercy killing") but believes that active-assisted dying and passive-assisted dying or not as distinct as often believed when individual circumstances are closely examined. For instance, Küng believes that if a doctor provides an overdose of morphine to a patient that causes them to die is viewed by some as an act of mercy and others see the same as a criminal act. Küng does not say that every assisted suicide is moral but instead argues that doctors who perform assisted suicide should not be as strictly judged and that individuals who are suffering from chronic illness should be allowed to choose assisted suicide for themselves and therefore there should be far less legal prohibitions of doctor assisted suicide and far less general condemnations of people who choose assisted suicide. I am concerned that legalizing active-assisted dying may lead to pseudo-assisted dying that Küng strongly condemns, especially for people unable to make the choice for themselves because they are in a vegetative state already, so I'm not advocating for complete legalization of it and agree that it requires medical oversight and legal regulation, but also think that the current laws and public opinion of assisted suicide is far stricter than is justified.
Küng specifically names Karen Ann Quinlan as an example, but there are many others people such as Terri Schiavo, Jack Kevorkian, and most recently Brittany Maynard that unfortunately polarized the question of whether anyone has a right to die via assisted suicide. In general, I agree that more compassion is needed and less judgment, especially in the particular cases for which Küng advocates.
Hans Küng writes: "If we look more closely, the gray areas in the process of distinguishing between active and passive assisted dying increase in size. Is the breaking off of a life-preserving medical aid—for instance, the disconnection of a heart-lung machine—an active or a passive aid to dying? From the standpoint of the effect (oncoming of death), the termination of active treatment (normal dose of morphia and stoppage of artificial feeding) can be precisely the same thing as active treatment (overdose of morphia). What can be clearly distinguished conceptually often cannot be kept apart in the concrete; here the boundaries between all these ideas of aid—between active and passive, natural and artificial, life-preserving and life-terminating—are obviously fluid." 
Assisted Suicide: The Right to Live with Human Dignity
Hans Küng justifies assisted suicide by an appeal to human dignity. He believes that a human being has the right to live a life with human dignity, because he believes that human life matters, and a human being should not be forced to continue unnecessarily a diminished form of living when assistance is available to them.
No advocate of a more active assisted death [i.e. Assisted Suicide] thinks that the person becomes "nonhuman" or "no longer human" as a result of incurable sickness, senility or definitive unconsciousness. On the contrary, precisely because man is and remains human, he has a right to live a life worthy of a human being and to die with human dignity, a right that may possibly be denied him if he is continually dependent on surgical apparatus and medicaments: that is, when all that is possible is to go on merely vegetating, to sustain a merely vegetative existence. In this light non of the three partial objectives of assisted dying—prolongation of life, diminishing suffering and preservation of freedom—may be made absolute, but must all be brought into harmony with each other. 
Objections to Assisted Suicide
In Eternal Life?, Küng answers the most common objection, that people do not have the right to determine when they die, and it is for god alone to determine when a person's life should end. Küng says this objection is false, by an analogy of death to birth. Küng reminds us that not long ago, all forms of artificial birth control were opposed, because of the common belief that only God determines when a person is born (and when they die), and many theologians argued that using birth control directly murdering a vast tree of descendants, because they were prevented from being born. Today the reverse is true, artificial birth control is generally accepted because it has finally been acknowledged that God has placed the beginning of life under humanities control. Likewise, Küng believes that a person's death is likewise placed by God under human responsibility, and that we also do control the circumstances of our death as well.
At one time many moral theologians interpreted and rejected active, "artificial" birth control as a denial of God's sovereignty over life, until they had to admit that the beginning also of human life had been placed by God under man's responsibility (not at his arbitrary choice). it is conceivable that the end too of human life has been placed more than hitherto under the responsibility (not at the whim) of man by the same God, who does not want us to shift off onto him a responsibility that we ourselves an and should bear? 
Küng also provides a list responses to other common objections:
Objection: Human life is God's 'gift,' certainly.
Response: But is it not also—according to God's will—man's task?
Objection: Human life is God's 'creation,' certainly.
Response: But is it not—according to the Creator's mandate—also man's responsibility?
Objection: Man must hold out to his 'appointed' end.
Response: But what is the end appointed?
Objection: A 'premature withdrawal' of life is a human refusal of the divine consent.
Response: But what is the meaning of 'premature' when we are speaking of a life that has been destroyed physically or psychologically? 
Küng does not advocate for assisted suicide in every circumstance, such as when a person is in despair after losing their first love, or when a person is tired of living due the weariness of life. Küng says that assisted suicide is an option for persons suffering from incurable diseases leading to death, especially those that progress into a vegetative state of life. In recent interviews Küng explains that he is in his 80's and has Parkinson's disease, that he has considered choosing doctor-assisted suicide in the future, after he is no longer to read or function a normal life due to his disease. So in the end, Küng says yes to assisted suicide, and this is a very important word, especially to people who are currently suffering in the situation that Küng describes, and this may be a word of encouragment to those individual's as well as their assisting doctors, who otherwise may feel condemned for choosing assisted suicide.
What I am advocating then is permission not for mercy killing but for a reflection on human responsibility even for dying and for a little less fear and nervousness about decisions in this respect, both on the side of the patient and on the side of the doctor. I am advocating man's responsibility, particularly from a specifically theological viewpoint, which attempts to take seriously belief not merely in a temporal, but also eternal life. 
I personally am sympathetic to Küng's argument for assisted suicide, and believe that it should ultimately be the choice of those individuals who are suffering, and their assisting doctors, to determine the moral choice, and that it is wrong to believe that assisted suicide always violates Christian ethics.
1. Hans Küng, Eternal Life?: Life After Death as a Medical, Philosophical, and Theological Problem, Collins: 1984. p. 165.
2. Ibid. p. 166.
3. Ibid. p. 167.
7. Ibid. Hans Küng. pp. 167-8.
8. Ibid. p. 169.
9. Ibid. p. 169.
10. Ibid. p. 170.
11. Ibid. pp. 168-9.
12. Ibid. p. 170.
^. Header Background is a picture of Brittany Maynard, holding her prescription drugs that she used to end her life in 2014: https://www.youtube.com/watch?v=yPfe3rCcUeQ#t=2m32s
Related: Active Assisted Dying, Assisted Dying, Assisted Suicide, Christian Ethics, Eternal Life, ethics, Euthanasia, Hans Küng, Passive Assisted Dying