EDMONTON -- A judge is to deliver sentencing later this month -- anywhere from time served to life in prison -- for a man convicted of killing two Alberta seniors who disappeared on a camping trip.

Travis Vader was found guilty of manslaughter in the 2010 deaths of Lyle and Marie McCann.

The couple, in their late 70s, vanished after leaving their home in St. Albert, northwest of Edmonton, on a camping trip to British Columbia. Their burned-out motorhome and a vehicle they had been towing were later discovered.

Their bodies have not been found.

A sentencing hearing that began in December wrapped up Wednesday. Justice Denny Thomas said he will be ready with a decision Jan. 25.

Thomas has described Vader as a desperate drug addict who came across the McCanns in their motorhome near Peers, Alta., and killed them during a robbery. The seniors were "truly innocent users of the highway" before they met up with the 38-year-old stranger, the judge said.

The Crown is asking for a life sentence, saying Vader was out on bail and on the run on other charges when he killed the vulnerable couple. He also showed no remorse after the killings, using their cellphone the same day to call an ex-girlfriend and their money to buy beer and a phone card.

The defence is arguing that Vader should receive four to six years but get at least six years credit for pre-trial custody.

"The circumstances of this case very much boil down to speculation. Nobody knows what occurred," lawyer Nathan Whitling explained to reporters outside the courthouse.

"The McCanns' remains have not been found, there were no witnesses there at the time and so it is impossible to say exactly what actions resulted in their deaths," he said.

"Given that the onus is on the Crown to prove aggravating circumstances, our view is that the matter must be presumed to be in the lower category of offences."

The time Vader has spent in custody on the case is complicated. He was arrested on outstanding charges when the McCanns disappeared but was not charged in their deaths until 2012. The Crown stayed murder charges before a trial in 2014, then reactivated them months later.

Vader has also been released on bail and had bail revoked, and has been convicted and sentenced and various other charges.

Whitling is further arguing that Vader should receive extra credit -- at times three-to-one credit -- because his constitutional rights were violated while in custody.

Vader testified over several days that he was subjected to a humiliating strip search, was denied proper access to a lawyer and was assaulted by guards and suffered other cruel conditions while behind bars.

Thomas dismissed part of the application dealing with the strip search, saying Vader has credibility issues, but has yet to rule on the other two grounds.

Bret McCann has said it's absurd that the defence is suggesting such a low sentence for the man who killed his parents.

McCann has been a fixture throughout the trial and sentencing hearing but, because it went longer than scheduled, has gone to Australia with other relatives. Thomas ordered that the family be able to watch his sentencing decision by video link.