Demonstrators of the organization Compassion and Choices stand in protest in front of the US Supreme Court in Washington, DC in 2005.Getty

When 45-year-old Belgium twins euthanized themselves last month after learning they were going blind, it renewed a debate about the legalization of physician-assisted suicide.

Belgium is one of only three countries that has legalized the practice. In the United States, Oregon passed its Death with Dignity Act in 1994, which allows physician-assisted suicide for patients with less than six months to live. Washington passed similar legislation in 2008, and a 2009 court ruling in Montana also legalized assisted suicide in that state.

The Belgian case was exceptional because the twins were not terminally ill. Belgium allows physician-assisted suicide when the patient declares it to be his or her wish and doctors confirm that the patient is in unbearable physical or psychological pain. The first doctors the twins approached refused the case; eventually, the deaf twins successfully argued that being unable to communicate with each other constituted unbearable psychological pain.

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In the United States, the debate permeated the 2012 election season in Massachusetts, where a Death with Dignity referendum question was narrowly defeated. While legislation as loose as that in Belgium appears unlikely to ever pass in the United States ("Their physician would be prosecuted here, and so would the pharmacist," Death with Dignity National Center executive director Peg Sandeen said), the discussion of whether to extend Oregon's and Washington's legislation will likely continue.

Both sides of the debate point to the close Massachusetts vote as a sign of success: The measure was defeated by 51 percent of voters.

"If you look at us like you might look at a social movement, we're very young," Sandeen said. "Having two states and a Supreme Court decision in our favor is really remarkable public policy accomplishment for legislation of this magnitude. We were outspent 7-to-1 in Massachusetts, and we still got [almost 50] percent of the vote."

The fear behind legalizing physician-assisted suicide is, in part, that it would lead to a slippery slope in which disabled or mentally ill populations would be vulnerable.

"Once adopted as a public policy desired outcome, how is it possible to observe or maintain parameters or constrictions on euthanasia or assisted suicide? That question should raise grave concerns, even for those who may want to offer some support for these concepts," said MC Sullivan, a lawyer, bioethicist, nurse and Director of Ethics at Covenant Health Systems, who worked for the Catholic church and a council of churches in the campaign against the Massachusetts legislation.

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"Why would we in any context set as a desired outcome? With such an irreversible action, where there's no woulda/coulda/shoulda, it is just both common sense and good public policy that that ought to be the last resort."

Belgium became the second country in the world to legalize physician-assisted suicide in 2002, and is considering additional legislation that would be "extended to minors if they are capable of discernment or affected by an incurable illness or suffering that we cannot alleviate."

"What started in the Netherlands, a policy about an informed decision by dying patients, has now devolved into an option being considered therein the case of severely disabled children --- who cannot themselves make informed decisions, and for whom the decision might be made by the physician, and in Belgium, an act carried out on people who are not even terminally ill?" Sullivan said.

In Belgium, 1,133 assisted suicides were reported in 2011. That compares to 141 cases in Washington and Oregon combined; the population of Belgium at the time was 11,008,000, similar to the combined 2011 populations of Oregon and Washington (10,701,897).

Supporters of Death with Dignity say that the U.S. legislation has provisions in place to protect against misuse: the patient must make two oral requests 15 days apart, for example, and a written request. If mental illness is suspected, the patient must also be referred to counseling.

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"There's no evidence of coercion," Sandeen said. "It hasn't happened in 15 years."

In fact, while some predicted that Oregon would become a "death destination" after the legislation passed, few people use the law. Of 114 people who requested lethal medication in Oregon in 2011, only 71 actually used it and died. Wayne State University professor Li Way Lee wrote about The Oregon Paradox in The Journal of Socio-Economics in 2010, exploring why "people who are terminally ill often feel a surge in well-being and hope to live longer when they have the option of legally ending their lives."

"It's the idea that people who have better control may actually have a longer life; they're getting good palliative care and they've stopped aggressive medical treatment," Sandeen said.

Regardless of physician-assisted suicide laws, both sides agree that good palliative care should be a goal for end-of-life care.

Before considering legalizing physician-assisted suicide, Sullivan said, other avenues should be exhausted: better pain management, better palliative care, better end-of-life conversations.

"With good palliative care, what happens is patients and loved ones are free from pain and suffering and are able to find new meaning and relationships," Sullivan said. "I've seen that; I know what palliative care can do. We need to spend our efforts and resources on that."