Four years ago, Jason Klaus told CBC News he cried himself to sleep every night.

He had just lost his parents and sister in a house fire, and in an exclusive interview on Christmas Eve 2013, Klaus insisted he had nothing to do with their deaths.

"No, I did not start this fire," he said angrily during a telephone interview. "I had nothing to do with this fire."

"I had nothing to do with killing my parents, if they did get murdered."

The medical examiner ruled in February 2014 that the three deaths were homicides. Klaus was charged months later.

On Tuesday, he will face a judge in Red Deer as his trial on three counts of first-degree murder begins in Court of Queen's Bench.

A friend and associate named Joshua Frank will be tried at the same time on the same charges.

The body of the dog that belonged to Gordon and Sandra Klaus was found outside the burning farmhouse. Joshua Frank is charged with shooting and killing the pet. (Facebook )

Frank faces an additional charge of injuring or endangering an animal for shooting and killing the family's dog. The pet's body was found outside the burning house.

It took RCMP more than eight months to lay charges against the two men. At the time, RCMP Insp. Tony Hamori said investigators had reason to believe the killings were planned and premeditated.

Hamori told the media the discovery of a "key piece of evidence" led to the charges. He refused to reveal what was found when dive teams were deployed in July 2014 near Big Knife Provincial Park, 190 kilometres southeast of Edmonton.

Mr. Big sting part of RCMP investigation

A recent court decision revealed that a so-called Mr. Big sting was part of the RCMP investigation. It's not known if that police operation led to the discovery of the "key piece of evidence."

The decision, written by Court of Queen's Bench Justice John Little, was in a response to a pair of defence applications to have the murder charges stayed because of excessive delay.

"Where the allegation is that an accused and his friend killed the family of one of the accused, possibly in a particularly cruel manner," Little wrote, "I must balance the rights of the accused to a trial within a reasonable time against the right of society to have a serious case heard on its merits."

Little also revealed how detailed and complex the trial will be.

The details of the RCMP undercover operation are expected to emerge at trial.

Mr. Big stings are controversial operations in which undercover officers pose as criminals to draw confessions from suspects. In 2014 the Supreme Court of Canada placed stricter rules on them, but did not forbid them.

In addition to the Mr. Big evidence, Little said the Crown is expected to call at least seven experts to testify about identification, firearms and arson. The judge said the case includes 16,000 pages of disclosure, 47 statements and 187 hours of audio and video.

To make matters more complex, the farmhouse fire that claimed the lives of Gordon, Sandra and Monica Klaus was so intense the remains of Sandra Klaus have never been found.

The Klaus family farmhouse burned to the ground on Dec. 8, 2013. The remains of Gordon and Monica Klaus were found inside, but Sandra's remains were not found. (Lisa Joy/Blackfalds Life )

The judge noted that fact "leads to additional problems of proof for the Crown."

The trial was originally supposed to be heard by a judge and jury. But after Little released his decision on the Jordan applications, lawyers from both sides agreed for the case to be heard by judge alone.

Justice Eric Macklin will preside over the six-week trial.

Klaus and Frank have been in custody since they were charged in the summer of 2014.