Lawyers for a man convicted of murdering two older Alberta whose bodies were not found sought a new trial.
In January 2017, Travis Vader was sentenced to prison for murder of Lyle and Marie McCann.
Attorneys have asked for a first-instance court proceeding to make a number of mistakes during the original proceedings.
Judges said on Friday that the trial lasted too long and that convictions should be interrupted.
Lawyers argued that the judge misused the outdated section of the Criminal Code, and later replaced the murder because of the initial suit of murder in the second instance.
The McCanns, who were in the late 70's, disappeared in 2010 after leaving their home in St. Alberta to go camping in British Columbia.
The Appellate Court reserved its decision.