So it's like based on facts and supported by evidence instead of just human moral or religious beliefs.
When a person becomes a doctor, they take the Hippocratic Oath. This oath is a promise that they will treat all people ethically. Euthanasia is an issue here because when a doctor "assists" a human being in the dying process their ethical duties as a doctor are questioned.
I assume that you would put discussions of rights under the same category as "moral or religious beliefs" and so you would not want arguments based on human rights.
In that case, your best bet is to look at arguments based on the likely impact of assisted suicide laws on people other than the ones who want to die. For example, the two links below go to articles that argue that assisted suicide/euthanasia would either A) improve health care for the terminally ill or B) cause the terminally ill to be pushed into killing themselves. These arguments are not really ethical/moral. Instead, they have to do with how legalized euthanasia would impact people other than those who want to die.