McCluskey was alone with the couple inside the trailer when gunshots rang out and the Haases' were killed, according to court documents.
The fugitives drove the trailer to a more remote spot, unhitched it and used liquor they found inside to set it ablaze. Investigators found the Haases' remains along with three bullet casings among the charred debris. Gone were the couple's truck, money and guns.
Province was captured days later in Wyoming, and McCluskey and Welch were taken into custody at a campground in Arizona.
After being questioned by federal agents, McCluskey said he shot Gary Haas once and Linda Haas three times.
McCluskey's attorneys have implied that they plan to present evidence that he has a mental defect or disease. They have indicated in court filings that they might call to the stand a forensic neuropsychologist who performed clinical tests on McCluskey. Some of the tests assess a person's planning ability and could be used to show lack of intent.