The senator who is sponsoring the government's physician-assisted dying bill says the Red Chamber already has about 50 proposed amendments ready to go – a number that could climb as high as 70 as senators decide whether to overhaul the legislation.

Senator George Baker, a Liberal, said the amendments, which will be debated beginning on Wednesday, come from Liberal, Conservative and independent senators and deal with every section of Bill C-14. He said most changes would make the legislation more permissive than the Liberal government's version, which passed in the House of Commons last week.

To make it into law, the bill must also pass in the Senate. Until it does, assisted death in Canada will be governed by the parameters set out in last year's Supreme Court ruling and provincial regulatory bodies rather than the Criminal Code.

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The Senate is expected to debate changes to the bill until at least early next week. If significant amendments are made in the Senate, the bill must go back to the Commons for a review – a process that could result in legislative "ping pong" if neither side relents.

"We don't know how this is going to end up," Mr. Baker, a 43-year veteran on Parliament Hill, said in an interview.

"When you go with independence in the Senate, you cannot predict the outcome."

Mr. Baker said the process could drag on indefinitely, if the House rejects the Senate's amendments, and vice versa. "This could go on forever," he said. He added that Parliament could end up sitting until July at least.

One potential option for resolving a conflict between the House and the Senate is a little-used Parliamentary procedure known as a "conference" – in which select members of both houses get together and try to end a legislative impasse. Such a conference has not been used in Parliament since 1947, and there have been only 16 since 1903. If negotiations fail, the bill could eventually die away.

Mr. Baker predicts the Red Chamber will have little appetite for negotiations.

"Because there is such diversity of opinions on the bill, this is not going to be an easy procedure," he said.

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Liberal House leader Dominic LeBlanc said it is still not clear what – if any – amendments the Senate will adopt.

"We're not wasting a great deal of time planning for scenarios that may not materialize," he said in an interview.

"I don't know if it will be significantly amended. I don't know if it will be amended at all. There may be amendments with which we could agree. … There may be some that the House of Commons will not agree to. But let's actually wait until it's amended."

Leaders of the Senate's Liberal and Conservative caucuses have said they believe the bill in its current form is unconstitutional because it restricts the procedure to patients in an "advanced state of irreversible decline" and whose "natural death has become reasonably foreseeable."

Senate Liberal Leader James Cowan plans to introduce amendments including one that removes the end-of-life criteria and uses only the language of the Supreme Court – that a consenting adult with a "grievous and irremediable" medical condition, suffering intolerably, can access the procedure. He also wants the bill to include advance requests for those with serious medical conditions that will lead to loss of capacity in the future, such as dementia.

Mr. Cowan said he has had no discussions with the government about compromise on the bill.

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"They say they are interested in thoughtful amendments from the Senate, and that's what we'll provide," he told reporters on Tuesday.

Conservative Senate Leader Claude Carignan says it is "impossible" the bill will pass in the Senate without amendments.

"I think that amendments on the constitutionality, it's probably the more important amendment we will insist [upon]," he said.

Other senators want to strengthen the bill's safeguards and make it more restrictive.

Conservative Senators Denise Batters and Don Plett want the bill to apply only at the end of life and for terminal illness, and to have stronger protections for the mentally ill and additional safeguards for medical professionals who refuse to participate.