Justice Denny Thomas has substituted two murder convictions against Travis Vader with manslaughter.
Lawyers returned to court in Edmonton to argue about whether there should be a mistrial because Thomas used an outdated section of the Criminal Code in his original verdict.
Thomas told court he made a mistake when he convicted Vader last month of second-degree murder in the deaths of Lyle and Marie McCann.
READ MORE: No Camera in court Monday for Vader
The McCanns, in their late 70s, disappeared after setting out on a camping trip from their St. Albert home to British Columbia in 2010.
But in finding Vader guilty, the judge used Section 230 of the Criminal Code, which the Supreme Court declared unconstitutional in 1990.
A sentencing hearing will be held December 12th.
Pictured: Travis Vader