An Edmonton judge denied a mistrial application Monday in the Travis Vader double-murder case, and instead convicted him of manslaughter in the deaths of an elderly St. Albert couple.

Bret McCann, son of Lyle and Marie McCann, said overall, his family is pleased with the judge’s decision.

"We’re comfortable that justice is being served," he said. "I understand the reasoning behind why he had to go to manslaughter instead of second-degree (murder).

"I was quite relieved we didn’t have to go through another trial."

During the application for the mistrial Monday morning, Justice Denny Thomas said he "accepted" that his conviction of Vader for double murder based on section 230 of the Criminal Code was an error.

READ MORE: Travis Vader found guilty of 2nd-degree murder in killing of Lyle, Marie McCann

In September, Thomas said in his verdict that Vader was a desperate drug addict who came across Lyle and Marie McCann in their motorhome and shot them during a robbery in 2010.

But in finding Vader guilty, the judge used Section 230 of the Criminal Code, which the Supreme Court declared unconstitutional in 1990. The government didn’t remove the section from the books, as antiquated laws are rarely repealed.

WATCH: Travis Vader was convicted Monday of manslaughter in the 2010 deaths of St. Albert couple Lyle and Marie McCann. Kendra Slugoski reports live from the courthouse during Global News at Noon. 

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Section 230 allowed for a second-degree murder verdict if a killing occurred during the commission of another crime, such as robbery. Otherwise, there must be intent to cause death or bodily harm that one knows is likely to cause death.

After Monday’s mistrial application, Vader’s lawyer Nate Whitling said he’s disappointed with the judge’s decision and expects to appeal it.

"It’s our view that Justice Thomas did not have the authority to do this and this is a matter that will have to be sorted out by a higher court down the road," Whitling said.

Whitling didn’t specify Vader’s reaction to the manslaughter conviction.

"Mr. Vader didn’t really have a chance to have a reaction. We saw him for just a couple minutes after court," Whitling said.

"Obviously it’s better than the original verdict, but our own view is that there needs to be a new trial all together."

Crown prosecutor Ashley Finlayson said he was happy the appropriate solution was found.

"For the Crown, our duty is to see that everything is done fairly so it’s not a matter of winning and losing for us, and this is just another step in the process," Finlayson said.

"In our submission, things have been working out in a satisfactory fashion."

During Monday’s application for a mistrial, Vader’s defence team told court a mistrial was the only option because "there just isn’t some other remedy that can fix this problem."

READ MORE: Travis Vader case: Crown urges judge not to declare mistrial

The Crown argued a mistrial should only be declared in the "clearest of cases and…this isn’t one of those cases."

The McCanns disappeared in 2010 while on a road trip. The elderly couple’s burned out motorhome was discovered a few days later near Edson, Alta., but their bodies have not been found.

Last week, Thomas said cameras would not be allowed in the courtroom for the mistrial hearing because he might not render a ruling on the application. He said the hearing would mainly consist of oral arguments rather than a scripted summary like he delivered the last time a camera was allowed inside.

READ MORE: Travis Vader case: Camera not allowed inside courtroom during mistrial decision Monday

Cameras were in the Edmonton courtroom when the judge convicted Vader in September.

Last week, the Alberta Crown said it was opposed to the idea of a camera in the courtroom during the mistrial decision.

A media consortium, which included Global News, applied earlier this month to have the camera present.

The sentencing hearing for Vader’s manslaughter conviction has been scheduled for the week of Dec. 12. The defence said it anticipates calling a "substantial among of evidence."

"He’s been assaulted by staff members, he alleges, and he’s been the subject of overcrowding and various other abuses, he alleges, by staff members. So we’re going to look into those allegations and see if they might form the basis for a sentence reduction," Whitling said.

The Crown said it will be asking for a sentencing "at or near the upper end of the range."

Bret McCann said he was pleased to hear the Crown will push for a lengthy sentence. He said he and his family will be at the sentencing hearing in December.

"His sentence and any sort of future parole considerations, I would think, would need to recognize his total lack of remorse," McCann said of Vader’s sentence.

The sentence for manslaughter ranges from a suspended sentence to life in prison.

With files from Caley Ramsay, Global News and The Canadian Press.