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Jury hears about DNA found on Renée Sweeney’s fingernails

Forensic expert testifies at murder trial of Robert Stephen Wright as to how DNA could have been transferred to Sweeney’s body on the day she was killed
Renée Sweeney. Supplied photo.

A forensic scientist with a specialty in DNA transference testified today, March 10, in the second-degree murder trial of Robert Steven Wright.

Wright is accused in the stabbing death of Renée Sweeney. Sweeney was murdered on Jan. 27, 1998 while at work in a video store located in a plaza at 1500 Paris Street. 

Crown co-attorney Rob Parsons called to the stand Renata Dziak, an expert in forensic DNA and “transferring persistence,” what Dziak described as the evaluation of how DNA is transferred. 

Specifically, in this case, she testified, she was asked to find the significance of the findings of the male DNA associated with the right fingernail clippings. 

The DNA associated with these clippings include two pieces of evidence that were a part of testimony on March 9. Manager of the biology section at the Centre for Forensic Sciences in Sault Ste. Marie, Tara Brutzki testified yesterday that she tested the many pieces of evidence from the Sweeney case during a full case re-examination she performed in 2013, when new technology had become available. She was able to isolate four samples of DNA, one being that belonging to Sweeney, the other being three different male DNA sources. 

One of those DNA sources was found on the right hand fingernails of Sweeney, and in the container that those fingernails had been stored in. It was a piece of brownish-reddish “debris” or what Dzaik today referred to as “cellular material.” 

Robert Steven Wright “could not be excluded as the source of these samples,” Brutzki testified yesterday. The likelihood that it is another random, unrelated person is one in greater than one trillion, or for the swabs, one in 8.2 million. 

Brutzki said March 9 there was a minor source on the nail itself, and a major source of DNA on the debris. 

Today Dziak went into further detail on the difference between minor and major, and the ways that the DNA, in this specific case, may have transferred onto Sweeney’s body. 

DNA can transfer through direct or indirect contact, she said, before offering examples of each. 

An example of direct contact, she testified, would be a person who cuts themselves and then another person, perhaps their partner comes to them and the blood then transfers onto the other person. 

Indirect contact, she said, would be the same situation but the injured person’s blood drips onto the floor and someone walks through it, picking the blood up on their foot or sock. She said that can then compound into the blood from sock onto a floor, for example. 

There is also the degree of contact to consider, said Dziak, either casual contact or contact with a degree of force. Casual contact, she testified, could be hugging, changing a baby, or even working in the same environment, like an office. 

As to contact with a degree of force, Dzaik was careful to note that “some degree of force does not imply violence,” simply the strength or energy as an attribute of physical action or movement.

She was asked to create a letter of opinion for the Crown, based on her expertise, to consider two alternative propositions based on the fingernail DNA evidence: was the DNA found associated with Sweeney’s fingernails deposited through close physical contact, a direct or indirect deposit of DNA at the point of contact of the nails — not any part of her, just contact with the fingernails — with some degree of force, or; the DNA was deposited through everyday casual contact. 

She testified that after reviewing peer-reviewed literature and considering her own 18 years experience in the field, she believed that the DNA was more likely left through contact with some degree of force, rather than through casual contact. 

Parsons then offered Dzaik hypothetical situations, noting however that she is unable to say how the DNA was deposited, or when. 

“Is this consistent with someone trying to offer first aid and she (Sweeney) came into contact with that person?” 

“I can’t rule that out,” Dziak replied. 

“How about alternative propositions?” said Parsons. "You can’t say that it is more or less likely that Ms. Sweeney was trying to fight off an attacker.”

“That is also a possible explanation,” Dziak testified. “However one of those scenarios is not more likely than the other.” 

She then detailed the amounts of DNA found, in nanograms. The nail itself had 11 nanograms, the debris had 73 nanograms. Parsons asked her if she would consider that to be a large quantity of DNA. 

"I would consider it to be a large amount of DNA," she said of the debris. "The majority of the population does not have foreign DNA under their fingernails, just walking around."

Dziak said she only encountered this amount of DNA “in under five cases,” and noted that even if she only tested the sample directly from the fingernail, not the debris, she would have the same opinion

Her opinion was "the DNA was more likely left through contact with some degree of force, rather than through casual contact."

On cross-examination, co-defense attorney Michael Lacy asked if an estimate of the quantity of DNA is an estimate.

“It is an estimate, yes,” replied Dziak. 

Lacy asked for agreement that the term "some degree of force" is difficult to define. Dziak agreed it was. “It’s not a well-defined parameter,” said Lacy, “it simply means more than very gentle contact, correct?” 

“Yes,” Dziak replied. 

Lacy compared the degree of force using the example Dziak had raised previously, but amended it to “changing a squirming baby,” and asked if this could qualify as some degree of force. “Under that scenario, that could be considered,” she stated.  

Lacy asked about preventative measures and protocols at the Centre for Forensic Sciences to avoid contamination, and if they had ever failed. 

“On rare occasions it has happened that despite protocols exhibits have been contaminated with DNA unrelated to investigation,” Dziak said. “A very rare event.”

When Lacy asked about the original collection method of the fingernails, Dzaik said she could only speak to their arrival at the centre, and she doesn’t know about how they were collected.

Lacy has raised the question of contamination of the fingernails in previous witness cross-examination. When he questioned retired Sudbury Regional police Sergeant Leo Thibeault about the removal of the fingernails during the post-mortem examination, Thibeault specifically remembered being the one to clip the nails. When pathologist Dr. Kelly Uren testified March 2, he believed that he, Uren, had clipped the nails. 

Lacy also asked retired forensics officer Rick Waugh about Sweeney’s hands, and whether they were covered or “bagged” before she was covered for body removal. Waugh testified her hands were not covered.  

Lacy also asked Dziak about the use of gloves while forensic scientists test evidence. She said she wears gloves and changes them with each new item. Lacy also asked OPP forensic Scientist, Sergeant Jefrey Myatt, about his pattern of changing gloves and whether, when he was an in-field officer, if he changed gloves and noted the change in his notebook. Myatt said he changed his gloves consistently, and that while some officers would note in notebooks when they changed, Myatt “never did.” 

Lacy also asked Waugh March 7 about changing his gloves while processing the scene. Waugh testified he changed his gloves, but did not note the change in his duty notes. 

Lacy asked Dziak about a statement she made in another trial, and asked if she agreed with it. "You agree with me that 'it would be an absolute overstatement to suggest that the quantity of foreign male DNA associated with the fingernails is from the perpetrator of the crime,” Lacy asked. 

“I do agree with that,” she replied.

When Parsons re-examined the witness, he asked Dziak if he could put two scenarios to her. 

“One, someone trying to render medical assistance and that person coming into contact with some degree of force, the second scenario of Sweeney scratching out at someone during assault. Is it an overstatement to say that your opinion is consistent with either of these scenarios?”

“One scenario is not more likely than the other,” said Dziak. 

Court ended at noon on March 10 and will resume on Monday, March 13 at 10 a.m.

Jenny Lamothe is a reporter at


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Jenny Lamothe

About the Author: Jenny Lamothe

Jenny Lamothe is a reporter with She covers the diverse communities of Sudbury, especially the vulnerable or marginalized.
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