Ontario's highest court is set to hear appeals of the two men convicted of the high-profile murders of Tim Bosma and Laura Babcock.
Dellen Millard is also appealing his 2018 conviction for murdering his father, Wayne Millard before the Ontario Court of Appeal.
Millard was to be ineligible for parole for 75 years and Smich for 50 years after judges imposed consecutive sentences.
But the two men will be entitled to reduced sentences after the Supreme Court ruled last year those types of stacked parole ineligibility periods amount to cruel and unusual punishment.
As a result, Millard and Smich will qualify for a reduced 25-year period of parole ineligibility, barring a successful appeal of their convictions.
The hearings before the three-judge panel are scheduled to last all week.