Blood and DNA that most likely came from murder victim Sheryl Lynn Koroll was found on shoes owned by accused killer Davey Mato Butorac, a jury was told on April 15.
Butorac is being re-tried for Koroll’s murder in New Westminster Supreme Court.
The Crown’s final witness in the case, police scientist Thomas Suzanski, testified about the various potential DNA samples seized when police suspected Butorac had killed Koroll in the summer of 2007.
Koroll, a 50-year-old Langley woman, was found dead in an industrial park off Mufford Crescent on July 7 of that year.
Crown prosecutor Wendy Dawson led Suzanski through the various samples, including swabs from the inside of Butorac’s car, and several pieces cut from Butorac’s shoe and shoelaces.
Suzanski first explained exactly how DNA tests tell apart different individuals.
The type of test used by the RCMP labs where Suzanski works looks at nine portions of DNA. Since most human DNA is identical, they look only at stretches known to vary between individuals.
If all nine sections, or loci, can be found, the tester can determine that there is only a small chance, based on how common those DNA sequences are, that the DNA came from any other person.
For instance, a swab from the passenger door of Butorac’s car showed that it had four of the loci that matched Koroll’s DNA.
That meant there was a 1 in 29,000 chance it came from anyone else. Given that there were more than 120,000 people in Langley in 2007, there could have been approximately four other people in the community with the same DNA profile.
However, tests on other samples turned up more conclusive results.
Two pieces of shoelaces showed that Koroll’s DNA was on them, and there was just a one in 200 billion chance that it came from anyone other than Koroll. All nine relevant strands of DNA were accounted for in that sample, as well as the double X chromosme that showed it came from a woman. Another minor trace of DNA in the same sample came from a man, but there was too little DNA to determine whose it was.
Another piece of shoe, this one positive for blood, also showed a mixture of male and female DNA. The female DNA matched Koroll, with only a one in two billion chance it was someone else.
Butorac’s defense lawyer, Richard Fowler, asked a few brief questions about the possibility that DNA on the door could have belonged to someone else.
He asked Suzanski if, had a fifth loci not matched Koroll, would that have excluded her from any match?
Suzanski said it would, but qualified that answer.
“All I can talk about is what I see, which is the four loci that are there,†he said.
Fowler also mentioned a report by another member of the forensic team on a swab from the inside of the trunk of Butorac’s car.
The jury has already heard how the RCMP found four drops of blood on the inside of the trunk during a thorough search. Carpet in the trunk had been torn out and the car had an almost spotless interior when police seized it for examination in the fall of 2007.
The sample from the trunk turned up two full loci and five partial loci, Fowler said.
Suzanski confirmed that between the full and partial DNA available, it matched Koroll with a 1 in 350,000 chance it was someone else.
The Crown’s case relies on forensics and circumstantial evidence, from DNA to tire and shoe prints found at the scene where Koroll’s body was located. Video footage at the scene showed a white vehicle, identical to the kind Butorac drove, left her body there.
This is Butorac’s second trial for Koroll’s death. He was originally found guilty, but a re-trial was ordered on this charge and for the murder of Gwendolyn Jo Lawton. The two trials are now taking place separately.