DNA analyst grilled by defence in Derksen trial

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This article was published 26/01/2017 (3471 days ago), so information in it may no longer be current.

The second-degree murder trial into the death of 13-year-old Candace Derksen is delving deeper into the DNA evidence that linked a suspect to the cold case two decades after the fact.

A scientist, who used up all of the DNA from the twine that had been tied around Candace’s wrists and ankles when her frozen body was found inside a shed in Elmwood in January 1985, testified Thursday that he believed it was “a good idea” to re-test the DNA extracts even though it meant using up the sample.

“I thought it would be prudent to run it again,” said Curtis Hildebrandt, a DNA analyst who was one of the founders of the Molecular World lab in Thunder Bay, Ont., where the Winnipeg Police Service’s cold-case unit sent samples of DNA for testing. The trial before Court of Queen’s Bench Justice Karen Simonsen heard previous DNA tests on the twine didn’t produce any useable results because there was such a small amount of DNA recovered.

Along with an actual piece of twine to swab, Hildebrandt received from police empty test tubes that had once contained twine — the trial previously heard the RCMP lab placed the twine in seven different test tubes.

He tried to extract any DNA that remained into a chemical solution he hoped would produce a higher concentration of DNA and lead to a complete DNA profile.

Mark Edward Grant’s defence team has previously suggested the fact the twine DNA sample was used up meant the lab’s results couldn’t be independently verified.

Although his previous test results were unusable, “there was something there,” Hildebrandt said, so he decided to run the twine extracts again.

The trial has not yet discussed the results of the DNA tests that ultimately linked Grant to Candace’s murder.

Grant was charged with Candace’s murder in 2007, and he was convicted after the case went to trial in 2011.

But the conviction was overturned after the Manitoba Court of Appeal ruled — in a decision upheld by the Supreme Court — that the initial trial judge erred by not allowing the jury to hear evidence that could have pointed to another suspect.

Hildebrandt’s testimony was cut short Thursday due to his cold and persistent cough, which caused him to begin to lose his voice and made it difficult for the judge to hear his answers and the questions being asked of him.

He testified he received several samples for testing from the Winnipeg Police Service in early 2007, including hairs seized from on and around Candace’s body and samples of blood and spit police had obtained from Grant.

The mitochondrial DNA tests — which trace maternal ancestry and can’t identify specific individuals, court heard — were able to exclude three of police’s potential suspects, including Candace’s friend and schoolmate who was one of the last to see her alive.

The mitochondrial DNA profile from Grant and his siblings — since all had the same mother — was common among Caucasians when compared to the FBI DNA database, Hildebrandt testified.

During cross-examination, Hildebrandt was grilled by Grant’s defence lawyer, Saul Simmonds, who suggested the lab had made a technical mistake involving DNA primers in its analysis and later did not correct the error.

Hildebrandt said he only found out about the mistake later — he couldn’t remember how — and didn’t know why no correction was ever issued. The mistake may have slightly affected statistical probability in the analysis, Hildebrandt said, but he said the overall results of the DNA tests would have remained the same.

Simmonds’ cross-examination of Hildebrandt is to continue Friday.

Portions of Hildebrandt’s testimony are subject to a voir dire, meaning it’s up to the judge whether they’ll be considered as admissible evidence.

katie.may@freepress.mb.caTwitter: @thatkatiemay