The Senate has gone to battle with the House of Commons to try to expand access to physician-assisted dying in Canada beyond what the Liberal government wants – the product of a more independent Red Chamber that is becoming impossible to predict.

In the first three days of scrutinizing Bill C-14, senators made three amendments – supported on all sides – including the significant step of removing the requirement that those who wish to die with the help of a nurse or doctor be at the end of life.

That would mean Canadians with non-terminal medical conditions or those suffering solely from mental illness could be eligible – a change the majority Liberal government has signalled it will reject. But since Prime Minister Justin Trudeau booted senators from the Liberal caucus and vowed to appoint only independent members, fewer votes follow party lines.

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Conservative Senate Leader Claude Carignan warned that if the House of Commons does not accept the Senate's changes, the bill stands the chance of being defeated.

"If they return the bill in its original form, the risk is high it will be rejected in the Senate," he said in an interview on Friday.

Even independent Senator Peter Harder, the government's representative in the Senate, says the Red Chamber is doing its job. "This is part of an independent, non-partisan Senate acting as it sees fit on an important and rather unique bill," he told reporters on Friday.

The other two amendments made this week would ban beneficiaries from helping a person self-administer medication or signing a request on their behalf, and require each patient to receive a palliative-care consultation.

But the major change to the bill was the amendment to scrap the government's requirement that a patient's natural death be "reasonably foreseeable" before they can qualify for assisted death.

A majority of senators voted to replace the end-of-life criteria with language from the Supreme Court of Canada, which ruled that consenting and competent adults who have a "grievous and irremediable" medical condition and are suffering intolerably are eligible for the procedure.

The Liberals have repeatedly defended the legislation as balanced, and say they are concerned about the lack of safeguards if end-of-life criteria are removed.

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But senators this week also rejected an amendment that would have required authorization from a superior court judge and an independent psychiatrist for patients who are not at the end of life, as well as a separate proposal for those with mental illness to undergo a psychiatric assessment and a 90-day waiting period. Two amendments dealing with terminal illness and stronger conscience rights also failed.

Independent Liberal Senator Serge Joyal, who moved the amendment to replace "reasonably foreseeable" death, said it was necessary to ensure the legislation is constitutional.

"We are here to protect, essentially, the minorities and to abide by the Charter of Rights decision of the Supreme Court. So personally, I think we should insist," he said in an interview on Friday.

When asked whether he will back down if the Commons rejects his amendment, Mr. Joyal answered: "No, not me."

More amendments could be made next week when the chamber debates advance directives – which would give those in the early stages of competence-eroding conditions such as dementia the opportunity to request an assisted death to be carried out in the future. The Liberal government considered and rejected the option, but vowed to study it.

Bill C-14 passed in the House of Commons at the end of last month, and this week the Senate began its third-reading deliberation of the bill. After the Senate finishes its changes, which could be next week, the legislation goes back to the Commons for further review – but it must eventually pass in the Senate to become law.

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If neither side relents, the bill could bounce between the houses, although the option of a mediation-style "conference" among select members could be used for the first time since 1947. Still, there is no guarantee an agreement would be reached.

Some senators are warning MPs to heed their suggestions, lest the bill languish indefinitely.

"The House should really pay attention to the amendments that we made," Conservative Senator Paul McIntyre, who supported the removal of end-of-life criteria, said on Friday. "This house is second sober thought, and this is why we're here."

But independent Liberal George Baker, a former MP who has been on Parliament Hill for 43 years, said he believes the Senate's will should never override that of the Commons.

"The big question is: Is the Senate going to respect the wishes of the elected house and say okay, we've made our point?" he said on Friday.

"This is something for the senators to have to seriously consider."