If selected from the ballot of Members' Bills, Maryan Street's 'End of Life Choice Bill' will open up the morally charged issues of physician-assisted suicide and euthanasia to Parliamentary debate for the third time since 1995.  And this time, the chances of the Bill making it to a successful third reading are higher than they have ever been.

Certainly, the trend in Parliamentary opposition to physician-assisted suicide has followed a clear path downwards.  Michael Laws' 1995 'Death With Dignity Bill' fared worst - voted down by 30 votes - although at the time the margin of opposition was attributed more to the Bill's authorship than its substance.

Peter Brown's 2003 version fared significantly better, missing out by only three votes.  Now, with public sentiment solidifying behind self-determination when dealing with end of life decision-making, Street's Bill looks likely to at least make it to a first reading.

But, the voices of opposition are far from stilled. The usual guardians of other people's morality can be relied upon to bring their clout to bear, while the Medical Association has declared on its website that euthanasia can never be considered an ethical practice even if it is a legal one.

This, and the appalled reaction of palliative care doctors to John Key's comment that "there's a lot of euthanasia that effectively happens in our hospitals", are indicative of what can be expected from health professionals should the Bill go any further.

But that's unsurprising.  End of life decision-making has always been an uncomfortable area for doctors, particularly from the point at which technology pushed back the boundaries of death without regard to quality of life.

Thankfully, too, doctors take seriously their role as life savers.  And those with a gift for recent history will be all too conscious of the slippery slope that began with the acceptance that there was such a thing as a life fit not to be lived and found its ultimate expression in complicity with the Nazi's forcible sterilisation or extermination of the medically unfit.  Understandably, it's not a journey that doctors want to be compelled to hazard again.

Technology, however, is no respecter of the sentiment and medical and legal casuistries have struggled to keep pace with the capacity of science to maintain 'life' beyond the point at which nature used to take matters out of all hands.  As a result, the medical profession has found itself dancing on the head of a philosophical pin, perhaps the most strained expression being that of 'double effect'.

This is the notion that justifies giving palliative treatment in order to relieve pain, while excusing any unavoidable but unwanted outcomes, death chief among them.  The emphasis of course is on the 'unwanted' bit.  It's a sort of medical mens rea - I wanted only to relieve the patient's pain, I didn't mean to kill them - that was just the side-effect.  

It doesn't take an ethicist to see that there are some pretty fine lines involved in this calculation and all of them are addressed (albeit with guidance) in a doctor's head.  

Given that, it's hard to justify the anger expressed by some physicians to Key's observation that euthanasia is happening in our hospitals.  As the Association of Salaried Medical Specialists was reportedly moved to say, euthanasia wasn't happening in the way the Prime Minister thought.  It was, the Association said, "more complex than that".

And so it is.  Add to all of this questions about withholding treatment ('passive' as opposed to 'active' euthanasia) and resource rationing and Key's comments were not far off the money.

At the very least it's clear that a comprehensive public debate about who should hold domain over our final moments is long overdue.  Street's Bill holds out that possibility and for this, if no other reason, it should be allowed to go to Select Committee.