Touching twine with bare hands a concern, DNA analyst at Candace Derksen retrial says

Details regarding the intricacies of DNA collection became so complex at the Candace Derksenretrial on Friday that at times, the judge had difficulty following the explanations and asked Mark Grant's defence lawyer to slow down.

Saul Simmonds, who is representing Grant accused of the 1984 killing of 13-year-old Candace continued his cross-examination of RCMP scientist Tod Christiansonat the retrial's fifth day.

Christianson prepared the twine used to bind Candace's wrists and ankles, along with other items found at the scene where shewas killed, for DNA testing.

Candace Derksen went missing on Nov. 30, 1984. Her body was found tied upin a storage shed near her house on Jan. 17, 1985.

In 2000, a number of items collected at Candace's autopsy were sent to be re-analyzed.

Simmonds asked Christianson to detail the methods and protocols around analyzing a DNA profile when the results came back from the RMCP's Ottawa lab in 2001.

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"When you're analyzing DNA we're talking about nanograms of DNA?" Simmonds asked Christianson.

"Correct," he replied. "[I] could analyze DNA you can't see."

At several points, Court of Queen's Bench Justice Karen Simonsen asked Simmonds to slow down because she was having difficulty following the complex nature of the process and terminology.

After a lengthy cross-examination, Simmonds raised the issue of possible contamination. He asked Christianson if he was wearing a mask when he was dealing with samples.

Christianson testified masks were not worn at the time.

"As careful as you are being you can potentially contaminate a sample," Simmonds concluded, and Christianson agreed.

Simmonds asked Christianson if handling exhibits with bare hands was a concern.

"It's obviously a concern," he told the court.

On Thursday, a knot analyst who initially examined the twine in 1985 testified he studied and "felt" the knotswithout wearing gloves.

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Tube of twine 'compromised'

Pamela Dixon was the RCMP scientist in Ottawa who received the twine and other exhibits from the crime scene Christianson sent for re-testing.

It was the forensic DNA technologist's job to conduct the test which would extract nuclear DNA from an item and generate a DNA profile for Christianson to analyze.

Dixon testified she received seven "large-scale extraction tubes" which contained the twine used to tie up Candace's body.

The tubes were sealed with a cap but Dixon testified "there was a compromise on one tube."

The relevance of that detail, if any, has not yet been made clear.

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Dixon explained how samples were stored in a locked, walk-in freezer unless they were being worked on.

She described how the twine was soaked overnight in an incubator. Court heard the twine was later moved with sterilized wooden applicators or "mini chopsticks" into "baskets" that are spun at high speed for roughly half an hour.

The DNA is later isolated with the aid of "harsh chemicals,"she said.

Dixon testified when conducting a large-scale extraction, as she was with the twine, the anticipation is that it will yield a low level of DNA.

She testifiedshe had to run a "quantification" test twicein order to try and collect enough in hopes of generating a profile to test for a match.

During each repeated process part of the twine sample is used up, she told court.

She obtained 7 nanograms of DNA. When the "genetic barcode" is generated through a process called amplication more of the DNA sample is "used up."

Dixon testified the twine would have contained 1.1 nanograms of DNA by the time the samples were returned to the RCMP lab in Winnipeg.

"It's approximately one billionth of gram," she confirmed.

DNA will be a critical topic in this trial because it is what led to accused killer Mark Grant's arrest in 2007.

A jury found Grant guilty of second-degree murder in 2011. Two years later, a Manitoba Court of Appeal judge ordered a retrial because evidence about a possible "third-party suspect" was withheld from jurors during the first trial.

Dixon's testimony and cross-examination continues this afternoon.

The judge-only retrial began on Monday. Brent Davidson and Michael Himmelman are acting for the Crown and Saul Simmonds is representing Grant.