"It's cutting your choice, not adding to it."
Physician-assisted suicide is legal in a handful of states, gaining momentum ever since the high profile suicide of cancer patient Brittany Maynard in 2014.
Many prominent Catholic leaders, such as Pope Francis, have spoken out against assisted suicide, calling it "false compassion." Archbishop Jose Gomez of Los Angeles has said assisted suicide "represents a failure of solidarity" and abandons the most vulnerable in society.
Callister's cases are not the first time patients have been denied care and offered death instead.
Stephanie Packer, a terminally ill wife and mother, was recently denied chemotherapy, but was offered assisted suicide by her insurance for just $1.20.
Packer said it was the ultimate slap in the face: her insurance company denied the coverage of critical chemotherapy treatment that her doctors recommended for her condition.
Particularly concerning is that the insurance company had initially suggested that they would cover the chemotherapy drugs. It was one week after assisted suicide was legalized in 2016 that they sent Packer a letter saying they were denying coverage. Despite multiple appeals, they continued to refuse.
Often, proponents of assisted suicide will argue it is necessary for people to avoid unending pain or unbearable suffering at the end of their life.
This argument ignores the advances made in palliative and hospice care which can control pain and symptoms at the end of life, Callister noted.
"In this day and age, we have outstanding palliative care, hospice care, we have the education, the skill and the drugs to keep you comfortable," he said.
Opponents of assisted suicide say there are not enough legal safeguards possible to guard against coercion and abuse, whether by insurance companies or by family members who may benefit financially from the death of a family member.
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"It's illegal for a family to coerce the patient. How are they going to regulate that? The coercion police are going to go to your house? It all sounds good on paper, but none of it is practically enforceable; it really isn't," Callister said.
Another argument used by proponents of assisted suicide is that they follow the same guidelines as do doctors for referring patients to hospice and palliative care – they only suggest assisted suicide for patients with a terminal diagnosis with six or fewer months to live.
But the problem with that, Callister said, is that doctors are often wrong when it comes to terminal diagnoses: the margin for error is 50-70 percent. Some patients die sooner than expected, while many also go on to outlive their prognoses, sometimes by years.
"My take on it is: if we're not sure how much quality time you have left, why would you throw that away? And the second part of that is once it becomes clear that you are dying, you're in your last weeks, we have the ability to keep you comfortable. So why do we need this law?"
He added that as a physician for 30 years, he has seen the end of life be some of the most important times in a family for healing, for reconciliation, for self-giving love.
"I see more self-giving love for other people, I see more families healed and brought together, and bad rifts healed and reconciled at the end of life than any other time."