As a strong general rule : We must do as much as possible to sustain the life of our loved-ones, and the option of euthanasia should only be brought into the picture under very extreme conditions, and after strict examination of our motives. We also have to note that in almost ALL cases when euthanasia (or mercy-killing) is even remotely considered, the persons involved would be subject to deep and immense emotional stress, fatigue, sorrow, etc, so much so that our judgment of said individuals should be of a very restrained nature. The absolute last thing a wife, who has just permitted the doctor to end her terminally ill husband's life, needs is a tongue-lash about her sin and bad ethical judgement, or an 'intellectual analysis' of what she 'should have done'.
There are generally two common reasons why people may seek to 'justifiably' end a sick or dying person's life (both of which may be subject to many factors):
1. To end his/her suffering
2. To halt the depletion of resources (personal or otherwise) in keeping the person alive
1. Euthanasia to eliminate suffering (present and/or future)
Strictly speaking, there should be no debate here. We are simply not allowed to make this call i.e. we are in no position to decide the value of a man's LIFE in relation to his SUFFERING. This applies, of course, to our own life as well. We have no right to decide to pull our plug (let alone others'!) based on the perceived excess and unbearable suffering the continuance of life will bring (how could we even 'measure' this?). Only God should be the judge of that.
These twin verses sum up the absolute Biblical command, especially in the face of extremely dubious (and impossible, IMO) value propositions between Life and Suffering:
Note too that mercy-killing is VERY DIFFERENT 'self-sacrifice' or 'martyrdom' whereby someone may forfeit his own life for the sake of others. In such cases, it is the welfare of another to which priority is granted, and for which one's life is willingly given up.)
To repeat : We have no right to terminate the life of anyone (even ourselves) based SOLELY on the motive of ending the personal torment of the individual involved, if only because our lives are 'not our own' (Job 1:21) and we cannot legitimately put any value to a 'trade-off' between life and suffering(!). God is the sole Author of Life and Death, and He alone will decide how much a particular life can and should go through before it expires.
With this in mind, we can address questions like:
Certainly we must do everything we can to ease the suffering, to love
and be with and encourage and counsel the person in question (assuming
he/she is still conscious). But ending the life of another in order
to stop his/her suffering is something which I believe we should not undertake,
in spite of our very sincere and heartfelt and intense desire to see the
person free from pain at last. Such is the
sacredness of the image of God in Man, that we should willingly surrender our loved-ones' pain and torment to God for Him to end in His own time.
Now we come to the other factor...
2. Euthanasia to halt the depletion of resources in keeping a patient alive
What if a severe amount of resources are consumed in keeping the person alive which, if completely or virtually depleted, could lead to seriously adverse effects on others? This issue is much harder from a theoretical - and I would think, practical - point of view, as now there are OTHER souls whose welfare we must consider apart from the sick/dying person in question.
One common framing of this issue would be: If a man is in a coma and the machine required to continue supporting his breathing everyday costs quite a lot, then should his wife, who (assuming) is not very well-off and who has kids to feed, continue paying for the apparatus even if there's NO SIGN whatsover of the husband recovering soon? Should the wife terminate the husband's life, failing which she may not be able to sustain her family? How is a mother's responsibility to care for her children compared to a wife's love for her husband (and not to mention the Exo 20:13 commandment)?
If it was just a decision on which life the wife should value more, then of course the husband comes out tops (Eph 5:31). But here we have to consider that the child's livelihood could be forfeited in a (possibly) fruitless attempt to sustain the husband.
Dealing with the 'easy' parts first (and ignoring any distinction between 'curable' and 'incurable' diseases), the decision to NOT perform euthanasia (at least in the short-term) should be LESS DIFFICULT if:
But what if a particular disease/sickness is irreversible or incurable?
My view is that pending strong revelation informing otherwise, if the
consensus medical opinion is that a patient either will not be able to
survive beyond a certain time or will not be able to survive without EXPENSIVE
life-sustaining equipment ('expensive' being that which goes beyond what
the family can reasonably afford without getting into severe financial
problems), then a decision for euthanasia may have to be considered.
The prime factor here is the confirmation of incurability which unfortunately
isn't without its ambiguities (see Geisler's Christian
Ethics, pg.167-171 for a fuller discussion. He also distinguished
'ordinary' and 'extraordinary' medical treatment, pg.171. I've preferred
to distinguish between 'expensive' and 'inexpensive' treatment as I feel
this better reflects the trade-off issues between continuing the patient's
life and caring for others in the family. And besides, most accepted
forms of 'extraordinary' would fall under 'expensive' too).
Surely this will be tough call to make regardless, and each one of us will have to give an account to God of our actions (Gen 9:5-6). Yet I believe that often the quality of our decisions depend very much on that of our character, which in turn is demonstrated by the convictions and principles which we bring to the decision. And failing any strict Biblical directive on such issues, I would quietly conclude if we have taken all primary factors (as noted above) into deep consideration and have prayerfully sought the Lord on this matter, then that de facto would represent a responsible life dedicated to Him.
And such a life is truly the goal to which God has destined us.