LONDON, Ontario — For Ron Posno, the signs were piling up that something wasn't quite right.

He had graduated with a degree in aeronautical engineering but suddenly struggled with simple arithmetic. The retired special-education teacher’s handwriting had become a scribble. The “homing pigeon” instinct that served him as a pilot was beginning to deteriorate. His sophisticated vocabulary was vanishing.

Then the 80-year-old got his diagnosis: mild cognitive impairment — sometimes a precursor to dementia.

“Everything I took 75 years to learn, I’m unlearning,” Posno said.

He had watched as the spouses of friends struggled with dementia. He thought about the end stages — and decided he didn’t want to put Sandy, his wife of 58 years, or himself through that “turmoil.”

So he put to paper eight scenarios that — were they to occur after he lost his mental capacity — would signal to caregivers that it was time for a physician-assisted death:

When I am unable to recognize family members, care providers or friends …

When I become persistently abusive …

When I am unable to eat, clean or dress myself without assistance …

“It’s not living anymore,” Posno said. “It is existing.”

Posno figured Canada, which in 2016 passed a federal law on what people here call medical assistance in dying, would be a place where he could set out his wishes to die on his own terms while he was still competent. As it turns out, “advance requests” like the one he tried to make are not allowed.

Now the government of Prime Minister Justin Trudeau has introduced a bill that would overhaul the process.

Polls show widespread support in Canada for broadening access. But much like the law it is intended to replace, the bill has faced criticism — for being too restrictive or too expansive or too confusing.

For Posno, “it failed dementia patients again completely.”

Some 13,000 people in Canada have received a medically assisted death since 2016, according to government figures.

The law allows such assistance for adults suffering from a “grievous and irremediable” medical condition and whose natural death is “reasonably foreseeable.” Patients must provide informed consent twice: when they first ask for assistance, and immediately before the cocktail of life-ending drugs is administered.

Canada’s law is more liberal than those of the U.S. jurisdictions where the practice is legal. In those jurisdictions, which include California, New Jersey and the District of Columbia, only mentally capable, terminally ill patients with a prognosis of six months or less who can self-ingest the drugs are eligible.

But implementing the law in Canada has not been without challenges.

Doctors puzzled over the definition of a “reasonably foreseeable” natural death. Ellen Wiebe, a physician based in Vancouver and one of the first in Canada to provide medical assistance in dying, remembers hashing out policies in email discussion groups.

Criticism exploded in 2018 over the case of Audrey Parker, a 57-year-old woman with terminal breast cancer that had spread to her brain. Fearful that the disease might rob her of the mental cognition to consent a second time, she scheduled her death earlier than she otherwise would have wished.

Doctors reported that patients were forgoing pain medication, even though it increased their suffering, so they could provide that second consent.

In September, a Quebec court struck down provisions that restrict medically assisted suicide to those with “reasonably foreseeable” natural deaths.

Rather than appeal the ruling, the federal government decided to change its law. Lawmakers asked the public to weigh in; more than 300,000 Canadians completed an online survey, overwhelming the site.

The bill before Parliament would create two tracks.

The first, for patients whose death is “reasonably foreseeable,” would remove a 10-day waiting period and allow patients who are approved to pick a date for their death and waive the requirement of a need for final consent.

The second would allow those with “grievous and irremediable” medical conditions that are not terminal to apply. Among other safeguards, they would be required to consent twice. Patients whose sole condition is a mental illness would be ineligible.

The proposal has received mixed reviews.

Wiebe said it would make a positive difference for her patients.

Trudo Lemmens, a law and bioethics professor at the University of Toronto, said the decision not to appeal the ruling was a mistake. Medically assisted suicide should be an “exceptional” procedure to “facilitate the dying process” at the end of life, he said, not a “tool to relieve the suffering associated with life” for those who aren’t terminal.

The Council of Canadians With Disabilities has warned that allowing physician-assisted suicide for non-terminal patients sends the message that “having a disability is a fate worse than death.”

Jocelyn Downie, a professor of health and ethics law at Dalhousie University in Halifax, Nova Scotia, cheered the waiver of final consent but called the exclusion of mental illness “stigmatizing.”

Rob Moore, Canada’s Conservative shadow minister for justice, said that the bill goes “far beyond the scope” of the Quebec ruling and that some proposed provisions “reduce protections for vulnerable members of our society.”

David Lametti, Canada’s justice minister, said he voted against the 2016 law because it was too restrictive. He said the new bill strikes the right balance between allowing people “to make a decision based on their own autonomous free will, but making sure as well that all the choices are there in front of them and that people who feel vulnerable won’t be afraid of having been unduly influenced.”

Justine Noel suffers from fibromyalgia, an incurable but not terminal condition that causes pain throughout her body. The 29-year-old is bedridden, and standing — even for a shower — is painful. Treatments have not helped.

The Niagara, Ontario, woman has applied for medical assistance in dying several times but has been turned down because her death is not “reasonably foreseeable.” She hopes to qualify under the new legislation.

“There have been people in my family that live up to 90,” Noel said through tears. “I don’t have 60 more years of this in me.”

Determining the eligibility of patients such as Noel will be one of the challenges of the proposed bill.

Tanja Daws, a doctor in British Columbia, said providing medical aid in dying is the “most meaningful” work she’s done.

“A lot of people have fibromyalgia but can have a very meaningful life and be extremely functional, and some people can be fairly debilitated by it,” she said. “It has a fairly high co-occurrence with mood disorders, such as depression. It will be one of those cases that we will have difficulty with.”

Jonathan Reggler, another provider in British Columbia, said cases such as Noel’s could be “quite stressful” for assessors.

“I know a number of my colleagues are concerned there will be certain patient groups . . . who will now recognize that they have some possibilities to be found eligible and they will be very difficult to assess,” he said.

Lametti said he understands the concerns. He said one of the doctors approving patients in the second track would need to be an expert in the condition.

The bill would deny access to mature minors, patients whose sole reason for requesting medically assisted suicide is mental illness and advance requests for those with illnesses such as dementia.

Lametti said that there’s insufficient consensus on these topics and that Parliament will study them this summer when a mandatory review of the law begins.

Of those subjects, Reggler said, advance requests are the most popular but are the “trickiest” to legislate.

Some dementia patients have been administered a medically assisted suicide, doctors told The Washington Post. The number is small because they must be sick enough to be eligible but not so unwell that they are unable to give final consent.

Saskia Sivananthan, chief science officer of the Alzheimer Society of Canada, said that the progression of diseases such as mild cognitive impairment and dementia are unpredictable, and that a patient’s condition can change rapidly without warning. They might lose their ability to give informed consent long before their death becomes “reasonably foreseeable.” The organization was initially opposed to advance requests, but it is now neutral.

Two government committees recommended allowing advance requests before the 2016 law was passed. Trudeau’s government declined.

A government-commissioned report in 2018 laid bare the challenges. Dementia patients may change as their condition progresses, the report said. They may overestimate how intolerable a future scenario is and then be unable to articulate if their desires change — creating uncertainty for the third party who has to decide whether to end their life.

“I’ve watched a number of people [with dementia] change their minds,” Wiebe said, “because they lost capacity and they no longer cared that they’re going to be in a care home for the rest of their lives.”

Ron and Sandy Posno met when they were in high school and married on a humid afternoon in August 1961. He remembers zooming off with his new wife in a convertible when it started to rain. She remembers their mothers meddling behind the scenes.

Sandy supports her husband’s wishes for assistance in death. She said his diagnosis has made them both more determined “to live life to the fullest.”

“When you look at what it’s like near the end,” she said, “I think it must be hell.”

Posno’s next assessment is in April. He’s bracing himself for news that his condition has deteriorated. He sees the advance request as a “beacon of hope.”

“I want to be remembered as a person who cared about living,” he said. “And who helped other people care about themselves and the life they could live.”