The jury at the Candace Derksen murder trial heard more complex scientific testimony when proceedings resumed on Thursday morning.
Mark Edward Grant faces a charge for first-degree murder in the case, which dates back to November 1984.
He has pleaded not guilty.
The case has focused largely on DNA evidence so far, and the lawyers on both sides argued about the reliability of the scientific investigation into the death of 13-year-old Derksen almost 26 years ago.
Testimony began Thursday with Arlene Lahti, a scientist who specializes in mitochondrial DNA and who was a founder of a company called Molecular World.
In spring of 2007, Lahti received samples from the Derksen case. They were blood samples taken from numerous people, she testified.
That group included Dave Wiebe and Audrey Fontaine, who have previously testified about being suspects years ago in the Derksen case.
In cross examination, defence lawyer Saul Simmonds questioned Lahti about the possibility of contamination of mitochondrial DNA.
Simmonds also asked Lahti about the data that can be learned from mitochondrial DNA, which can rule out a person as a match to another DNA sample, but cannot specifically single out one individual as a match, without the use of additional information.
The court previously heard that several hairs found at the shed where Derksen was found were analyzed for DNA.
However, Lahti did not personally testify about those hairs and did not make any comparisons between the DNA profiles she created with any other samples of DNA.
Derksen, 13, disappeared while walking home from school in November of 1984. Seven weeks later, her body was discovered bound and frozen in a shed in Elmwood.
