Scientist spoke about 'solving' Candace Derksen cold case before accused went to trial, defence lawyer says
Questions credentials of co-founder of lab responsible for DNA tests that led to Mark Grant's arrest
A senior scientist's qualifications and reliability were challenged at the Candace Derksen murder retrial Wednesday — and the defence even suggested she spoke publicly about solving the cold case while it was still before the courts.
"You were actually lecturing and telling people you solved this case by linking evidence to a single suspect," defence lawyer Saul Simmonds said to Arlene Lathi.
"No, I don't recall giving that information," Lathi told the court.
Lathi was a senior scientist, analyst and co-founder with the lab Molecular World, which tested the DNA that eventually led to Grant's arrest in 2007 for the murder of the Winnipeg girl.
Candace, 13, went missing on Nov. 30, 1984. Her body was found frozen and tied up with twine in an Elmwood storage shed nearly seven weeks later.
Grant was convicted of killing Candace Derksen in 2011, but the Manitoba Court of Appeal overturned the conviction two years later and ordered a new trial.
Lathi told court Wednesday she received DNA samples from other suspects, as well as from Grant's maternal siblings, and performed mitochondrial DNA tests — one of three kinds of DNA testing and a type unavailable to police in 2001 when evidence was originally tested — for RCMP to analyze.
She explained to court the step-by-step procedures involved in extracting mitochondrial DNA from the swab samples, purifying them and then copying them millions of times over to generate a DNA sequence or profile for each individual. The results were then forwarded to RCMP scientists to interpret and compare.
Scientist has no memory of lecture
Defence lawyer Saul Simmonds began his cross-examination by attacking Lathi's credentials.
"You didn't take any special training in forensics with respect to DNA," Simmonds said to Lathi.
Lathi told the court she had taken some forensics classes during her education and had done "some training" under a forensic specialist.
Simmonds pointed out Lathi had no PhD, and according to her testimony in 2011 no specialization in forensics. Lathi then told court she agreed.
The defence went on to ask Lathi about a speaking series hosted by the Health Sciences Foundation where she was listed as a lecturer in 2008 — a year after Grant's arrest.
According to an advertisement for the series, Lathi and a colleague were to discuss the technologies used to "help RCMP in Winnipeg to solve a cold case" where Molecular World "linked evidence to a single suspect," Simmonds told the court.
"You were discussing a case still before the courts as if you have solved it," Simmonds said.
"I could see how you would perceive that," Lathi replied.
Simmonds went on to suggest she and her colleague were using this case as an "advertising tool" to market Molecular World, a fee-for-service lab.
Lathi told the court more than once that she had no memory of this speaking series or giving this lecture.
"You have no memory whatsoever?" Simmonds asked again.
Lathi agreed.
Protocols questioned
The defence also raised questions about lab protocols, proficiency testing for lab employees and the protective gear worn to avoid contaminating the DNA Lathi was working with.
"Mitochondrial DNA is very susceptible to contamination," Simmonds asked Lathi to confirm. Lathi stopped short of agreeing but told court contamination is possible.
She explained she worked under a sterilized hood wearing a lab coat, gloves, glasses and a mask. She said proficiency testing was conducted internally and by a third-party organization, but could not confirm how often.
Simmonds also raised the issue of how "discerning" the results of mitochondrial DNA testing are because anyone with the same maternal lineage shares the same mitochondrial DNA profile, he said.
Lathi agreed.
"We might share a mitochondrial profile even if our families hadn't had contact over generations," Simmonds suggested to Lathi.
"That's one way to look at it," she said.
The judge-only retrial continues Thursday. Court of Queen's Bench Justice Karen Simonsen is presiding over the trial. Brent Davidson and Michael Himmelman are acting for the Crown and Saul Simmonds is representing Grant.
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