The judge who convicted Travis Vader of two counts of second-degree murder dismissed all of the analysis offered by the defence's DNA expert, calling him a "hired gun" who in one instance attempted to mislead the court.

In a decision delivered Thursday, Court of Queen's Bench Justice Denny Thomas said the murder trial into the deaths of St. Albert seniors Lyle and Marie McCann hinged, in large part, on the DNA evidence presented by the Crown.

Thomas said the defence, based on the testimony of DNA expert Randell Libby, "vigorously attacked" all aspects of the DNA evidence including its sampling, processing and analysis.

But Thomas found that attack unsuccessful on all fronts, and went further, sharply criticizing Libby's testimony and independent professionalism.

"I reject that Dr. Libby was a 'witness for the court,' " Thomas wrote. "He was an advocate for Mr. Vader.

"Dr. Libby was not an independent expert but instead acted as a hired gun for the defence," Thomas continued. "I therefore place no weight or value on his opinion evidence and his interpretation of whether Mr. Vader's DNA was recovered from the McCann SUV and its contents."

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The McCanns disappeared in early July 2010 after starting a summer road trip to British Columbia. Their motorhome was found in flames at the Minnow Lake campground near Edson, Alta., two days after the couple left on their trip. Their SUV was found several days after that. The McCanns' bodies have never been found.

Although the RCMP quickly focused on Vader as a murder suspect, it took almost two years before he was charged with two counts of first-degree murder.

During the trial, Vader's defence called Libby as an expert in forensic DNA analysis and various streams of genetics. The Seattle-based scientist is the co-founder of a company that specializes in prenatal genetic testing.

Thomas devoted several pages of his 131-page decision to picking apart Libby's analysis, calling it "backwards" and scientifically "wrong" at times. He produced charts to show how Libby's logic was flawed.

The judge was particularly critical of Libby's testimony that there was inconclusive evidence Vader's DNA was found on Lyle McCann's hat. The Crown argued, and Thomas accepted, that a 94.4-per-cent match was enough to conclude Vader's DNA was present.

Thomas said in that instance, Libby's analysis "can only be explained as an active attempt by the expert to mislead the finder of fact.

"Dr. Libby reframed his analysis in a manner that guides the finder of fact, me, who depends on his expertise, down a blind alley and away from the core question on which he was to assist: is that Mr. Vader's biological material on Lyle McCann's hat?"

Testimony criticized in previous case

Another judge from the same Alberta court had sharply criticized Libby's testimony in another trial less than two years earlier. The law firm that had hired Libby in the previous case is the same one that represented Vader in his murder trial.

In the earlier case, a sexual assault trial, Justice Juliana Topolniski found Libby provided no alternative to the Crown's evidence and, during cross-examination, "was unresponsive to simple and direct questions.

"It would be fair to condense Dr. Libby's testimony to one conclusion: 'It's complicated,' " Topolniski wrote in her decision. "That is not useful, particularly when it is unsupported by an underlying methodology, rationale, or scheme."

During Libby's qualification as an expert witness in the Vader trial, Thomas asked him if he recalled that sexual-assault trial.

The judge said Libby, who estimated he had testified in Canada only a handful of times, initially told him the case "doesn't sound familiar" but after Thomas pressed him with more details, Libby said he remembered the case.

In his decision, Thomas said he found Libby's initial response not credible.

"I find as a fact that Dr. Libby is well aware that his previous appearance in this court was not well received, and that he was less than forthright in his response to my inquiry," the judge wrote.

"He attempted to avoid that issue. This goes to his credibility."

The Crown had sought a conviction on two charges of first-degree murder. Thomas instead convicted Vader of two counts of second-degree murder.

Vader's lawyer, Brian Beresh, has already said he will appeal the ruling.