The couple who were convicted in 2016 in their toddler son's meningitis death in southern Alberta will appeal to Canada's highest court Tuesday to either overturn their convictions or order a new trial.

FOR THE LATEST ON THIS STORY: Supreme Court orders new trial for Alberta parents convicted in meningitis death of toddler

Court documents obtained by CBC News outline the arguments Collet and David Stephan plan to rely on during their appeal to the Supreme Court of Canada.

Their main argument is that the trial judge failed to deliver an appropriate jury charge.

The Stephans were living in Lethbridge when their 18-month-old son Ezekiel died in 2012.

The couple, who now live in Nelson, B.C., were convicted of failing to provide the necessaries of life following a trial in 2016.

Last November, the Alberta Appeal Court upheld the convictions. But because one of the three judges disagreed and found the couple should have been granted a new trial, the Stephans had automatic leave to have the Supreme Court of Canada hear arguments.

Original trial

During their 2016 trial, jurors heard the Stephans treated their son with natural remedies and homemade smoothies containing hot pepper, ginger root, horseradish and onion.

The Stephans refused to take the boy to a doctor even when he became so stiff he couldn't sit in his car seat.

Only when Ezekiel stopped breathing did the parents call 911. After days of being ill, he was eventually rushed to a local hospital but died after being transferred to Calgary.

Defence seeking new trial

In the documents obtained by CBC, the Stephans' legal team relies largely on the opinion of the Alberta Appeal Court judge who disagreed with their convictions and thought the couple should have been granted a new trial.

According to their factums, the Stephans' defence believes that the instructions given to the jury by the judge were inadequate.

"The jury instructions in this case provided virtually no assistance with respect to the analytical exercise the jury needed to perform," reads one of two factums prepared by the defence. "It did not identify the discrete issues the jury had to consider and it failed to highlight the evidence that was legally relevant to those issues."

Deficiencies in the jury charge, according to the defence team, included the judge not reviewing what the defence believes to be substantial aspects of evidence and linking them back to live legal issues, failing to caution the jury on the permissible and impermissible uses of expert evidence, not delivering the charge in plain language and that the charge relied on "boilerplate model instructions" without adapting them to the circumstances of the specific case.

"The appellant submits that for all of the foregoing reasons … the jury instruction contained reversible error and a new trial is required," reads the document.

'Attentive, loving parents'

The Stephans' defence team says the facts of this case are very different from most others where failure to provide the necessaries of life is charged.

"The appellants were attentive, loving parents who were actively attempting to fulfil their parental duties," reads their factum. "If their 'failure' was not taking Ezekiel to a doctor, it did not stem from eccentric beliefs or a distrust of 'modern' medicine as the Crown tried to allege."

Ezekiel Stephan died in 2012 from untreated meningitis. (Courtesy of the Stephan family)

The defence claims that the evidence instead established ongoing consultations with a medically-trained emergency room nurse as well as an urgent 911 call and subsequent trip to the hospital.

"The appellants were not trying to hide an injured child because they feared legal repercussions," reads the factum. "They did not take Ezekiel to the doctor because his symptoms appeared to be mild and consistent with a typical cold or flu. They were told by a medical professional that she could find nothing wrong with him."

According to the defence, the determination that the Stephans' conduct represented a marked departure from the standard of a reasonable parent was "compromised by a misleading, confusing instruction."

"An error which was compounded [by] inadmissible and highly prejudicial opinion offered by a number of medical doctors regarding what they would have done."

Confusing for jurors

The Stephans' legal team will argue that the trial judge's legal analysis, contained within a "single, 92-word sentence," was confusing for jurors.

"The trial judge had an obligation to provide the test in plain, intelligible language, that it would be accessible and comprehensible by the jury," reads the factum, adding that this was an issue noted by the dissenting judge in the provincial appeal process.

The defence will suggest that the jurors in this case would have had to weigh the evidence and answer no less than 22 discrete questions, including what level of risk was objectively foreseeable to a reasonable person in David/Collet's position when the failure occurred.

No lay person would have been able to identify the discrete questions necessary to evaluate each element of the offence. - Stephans' defence team

"No lay person would have been able to identify the discrete questions necessary to evaluate each element of the offence (much less isolate the evidence properly applicable to each question)," writes the defence.

Further, the defence suggests that the judge's instructions "failed" to adequately review the evidence, simplify it, or link it to relevant issues in the case.

"As noted in the dissent, the trial judge failed to canvass the 'circumstances' that presented to each of the appellants, failed to explain the permissible uses of the medical evidence, failed to draw the jury's attention to key defence evidence and failed to make it clear to the jury how they should assess whether or not there has been a marked departure."

Further, the Stephans argue that the judge took more time reviewing the Crown's evidence than that of the defence — something the first appeal found was because the Crown had simply called more evidence than the defence had.

David Stephan and his wife, Collet Stephan, arrive at a Lethbridge court in 2016. (David Rossiter/Canadian Press)

Alberta Crown disagrees

The factum prepared for the Supreme Court appeal by Alberta's attorney general (Crown) disagrees with the basis of the Stephans' appeal and says that no reviewable errors have been established.

"The dissenting judgment misapprehends the nature of the offence and fails to apply the appropriate standard for appellate review," reads the Crown's factum.

The Crown said the majority of the Court of Appeal is correct in that the specifics sought by the dissenting judgment are not required in this case.

"The dissent's suggestion that the trial judge should determine specific necessaries should have been provided and when, as a part of the jury instructions on whether there was a failure, invites a reviewable error and infringes on the jury's fact finding duties."

No assumptions were made about any elements of the offence. The charge cautioned the jury on the use of the expert evidence, sufficiently linked the evidence to the issues and was understandable. - The Crown's factum

According to the Crown, the Stephans' argument that the charge could have been worded or structured differently does not amount to a reviewable error.

"No assumptions were made about any elements of the offence," reads the Crown's factum. "The charge cautioned the jury on the use of the expert evidence, sufficiently linked the evidence to the issues and was understandable."

The Crown says that the majority of the Alberta Appeal Court, after reading the jury's charge as a whole, concluded, "the jury was properly instructed on the mens rea (guilty mind) element and the marked departure of a reasonable and prudent parent."

The Crown's argument insists that not only was the jury properly instructed, but the structure of a jury charge does not amount to a reviewable error and that the charge sufficiently related to the evidence.

"The essence of the appellants' argument is that the charge is deficient as the trial judge should have emphasized the defence evidence while minimizing the Crown evidence," said the Crown. "This is dangerously close to telling the jury how to weigh and consider evidence. In this case, the evidentiary review was balanced and sufficient."

Crown continues to seek increased sentences

Prosecutors are still asking the Alberta Court of Appeal to increase the couple's sentences. David was given four months in jail while Collet was given three months of house arrest.

CBC News has not been able to confirm if a date has been set for those arguments.