Being able to find research on such an intense topic is going to be relatively easy for you. There is much out there. Sorting through it might be a challenge, but this is not a topic where there is a lack of resources. The basic proposal is something that is quite relevant in the discourse right now. In writing the letter, I think that you have to carve out your position and proceed from there.
Essentially, this boils down to what facts you consider to be the most persuasive. The public opinion in Canada speaks to legalizing assisted suicide. The Canadian Medical Association has suggested that it "supports the right of all physicians, within the bounds of existing legislation, to follow their conscience when deciding whether to provide medical aid in dying.” Over 40% of Canadian doctors polled support the measure of legalizing assisted suicide, and over 70% of the public feels the same way. In laying out the case of assisted suicide being legal, I think that part of it resides in how respecting a patient's right to die shows the acknowledgement of their dignity: "...respect for persons demands respect for their autonomous choices as long as those choices do not result in harm to others." In laying out the case for medically assisted suicide, it might help to cite such philosophical tenets that lie at the base of the argument. At the same time, it might help to suggest that there is a movement in Canada to validate the right to allow medically assisted suicide. The original law called for a penalty of 14 years for any doctor that participated in such a venture. However as recent as 2012, the Supreme Court of British Columbia struck down this provision:
...the impugned provisions unjustifiably infringe s. 7 [and s. 15 ] of the Charter, and are of no force and effect to the extent that they prohibit physician-assisted suicide by a medical practitioner in the context of a physician-patient relationship". Moreover, the court found that the relevant sections were legislatively overbroad, had a disproportionate effect on people with disabilities, and were grossly disproportionate to the objectives it is meant to accomplish.
It becomes evident that the Supreme Court believes that criminalization of legally assisted suicide inhibits the relations between physician and patient. This might help to explain why there is a movement to reevaluate the debate and validate the proposal of legalizing medically assisted suicide.
On the other side of the issue exist the objections. Those who wish to continue the criminalization of the legally assisted suicide advocate that the needs of the few should not overwhelm the needs of the many:
The movement for the legalization of assisted suicide is driven by anecdotes of people who suffer greatly in the period before they die. But the overwhelming majority of these anecdotes describe either situations for which legal alteratives exist today or situations in which the individual would not be legally eligible for assisted suicide.
In arguing against the proposal, a utilitarian argument is advanced because the narratives of those who wish to die might not be reflective of the majority of individuals who will be impacted through the proposal's passage. Those against the passage of the proposal point to how there is a "slippery slope" in which the embrace of legally assisted suicide will move from terminal cases to issues of convenience:
This fear of disability typically underlies assisted suicide. Janet Good, an assisted suicide advocate who worked with Jack Kevorkian, was clear about this: "Pain is not the main reason we want to die. It's the indignity. It's the inability to get out of bed or get onto the toilet... I can't stand my mother- my husband- wiping my butt." But as many thousands of people with disabilities who relay on personal assistance have learned, needing help is not undignified, and death is not better than reliance on assistance. Have we gotten to the point where we will abet suicides because people need help using the toilet?
It is in this "slippery slope" element where a compelling case can be made against the passage of the proposal.
In writing your editorial or persuasive piece to the media, you need to determine which side is more compelling in terms of the written process. If this converges with your own personal point of view, that is fine, or if it does not, that, too, is acceptable. I think that you are writing this piece from what can be proven and what is most persuasive in your mind and how this resonates on paper. Using the sources is a guide, but in the end, developing the arguments is going to be critical in your piece. Progressing in this manner is going to be critical in constructing a newspaper piece that takes a strong and persuasive position on such a powerful issue.