2016-05-18 Defence experts question forensic evidence | St. Albert Gazette

Published by Bretton McCann,

Defence experts question forensic evidence

Blood spatter evidence suggests passive deposit, Vader DNA matches not proven

Wednesday, May 18, 2016 06:00 am

Comments    |   

A A

    .

Blood found on Lyle McCann's hat may not have been deposited as a result of force, a defence expert says.

Joseph Slemko, an Edmonton Police Service officer with blood-spatter expertise who testified as an independent consultant at accused murderer Travis Vader's trial on Tuesday morning, said the blood stains were more consistent with drops of blood falling from above as a result of gravity rather than major external force.

"It's a very large blood stain," he said. "The larger the blood stain, the lower the level of force."

He explained that in cases where blood is spattered by force, there tends to be more and smaller droplets in the resulting stain. In the case of the hat, he said the stains were instead consistent with blood falling onto the hat and hitting it perpendicular – any smaller spatters are likely a result of those drops.

"Sometimes blood spatter analysts misinterpret those smaller stains," Slemko said.

An RCMP expert testified earlier in the trial that the blood stains on McCann's hat were consistent with blood deposited as a result of significant force.

Defence lawyer Brian Beresh proposed the hypothetical scenario where Lyle McCann had a nosebleed, and dripped blood onto the hat.

"It would be consistent with that scenario, but all I can say in this case is a source of blood was above the hat," Slemko replied.

He also noted one of the challenges in determining how the blood came to be on the hat is that it is impossible to say for certain where the hat was when the blood was deposited.

Vader is accused of murdering St. Albert couple Lyle and Marie McCann on or about July 3, 2010, the day they were last seen. Their SUV was recovered two weeks later, and the Crown has presented DNA evidence linking Vader to items found in the vehicle, and even that a blood stain on the front centre armrest came from Vader.

Beresh also proposed a scenario for how Vader's blood may have come to be on the SUV's centre armrest, suggesting it could have been deposited there as a result of Vader coughing or sneezing into the vehicle through an open window.

"Consistent is too strong a word. I'd say it's possible. There's hundreds of other possibilities of how that got there," Slemko said.

With respect to the food cans found in the SUV that were found to have Marie McCann's blood on them, Slemko testified his first impression was that the blood had been diluted based on its appearance, and he believed it may have been deposited as a result of a cough or sneeze – but no tests were performed to confirm that.

He also said the Crown expert's conclusion the cans were together when blood was deposited by force being applied to a liquid source was not necessarily supported by the available evidence.

Crown prosecutor Ashley Finlayson was scheduled to begin his cross-examination after the lunch break.

DNA evidence

Slemko is the second defence witness to raise doubt about Crown experts' testimony.

Monday afternoon, defence witness Dr. Randell Libby began to address specific pieces of evidence and the uncertainty around conclusions drawn by RCMP analysts.

An RCMP expert testified the blood on the hat belonged to Lyle McCann, and said the hat also had Vader's DNA on it.

Libby said the limited information with which the RCMP analysts drew that conclusion raises significant doubt.

"The data is incomplete," he said. "I would regard this analysis as inconclusive."

Likewise with the other samples from the SUV the Crown has suggested came from Vader. In nearly every case, Libby argued the conclusions these samples came from Vader are going too far.

"I don't disagree that the overall profile is consistent with Mr. Vader," he said, but noted most of the samples are only partial and there's not a strong enough statistical connection to say with certainty they came from him.

The one exception is with respect to the Boxer beer can found in the SUV. Crown witnesses said it was all but certain that sample came from Vader, and Libby agreed. He noted, however, that one could not say for certain when or how that DNA was deposited on the can.









From Around The Province

Comments



NOTE: To post a comment in the commenting system you must have an account with at least one of the following services: Disqus, Facebook, Twitter, Yahoo, OpenID. You may then login using your account credentials for that service. If you do not already have an account you may register a new profile with Disqus by first clicking the "Post as" button and then the link: "Don't have one? Register a new profile". The St. Albert Gazette welcomes your opinions and comments. We do not allow personal attacks, offensive language or unsubstantiated allegations. We reserve the right to delete comments deemed inappropriate. We reserve the right to close the comments thread for stories that are deemed especially sensitive. For further information, please contact the editor or publisher.

http://www.stalbertgazette.com/article/Defence-experts-question-forensic-evidence-20160518