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Saliva and blood taken from Guylaine Potvin's apartment in April 2000

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Guylaine Potvin was killed in Jonquière in 2000.

  • Mireille Chayer (View profile)Mireille Chayer

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A forensic biologist, Caroline Paquet, explained to the jury during the trial of Marc-André Grenon that no trace of sperm had been taken from the body of Guylaine Potvin, murdered in April 2000 in Jonquière. However, saliva was taken, as well as blood on his t-shirt and on a belt seized from his apartment.

It was not Ms. Paquet who worked on the case of Guylaine Potvin at the time, but she based herself on the work carried out by two of her colleagues in order to prepare her testimony before the court, Wednesday morning.

Caroline Paquet has worked at the Montreal Laboratory of Forensic Science and Legal Medicine since 2005 and became coordinator unresolved cases in biology since 2021.

DNA is the basis of our work, she explained to the jury. She recalled that DNA is a molecule present in the nucleus of animal cells. It is found in the form of chromosomes. She said all human beings' DNA is 99 percent identical and forensic biologists look for variations in the remaining percentage point. It is with this variation that it is possible to establish the genetic profile of an individual.

Caroline Paquet told the jurors that his laboratory receives various pieces of evidence, such as objects or biological samples. These parts are subjected to analyzes in an attempt to establish genetic profiles.

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We work by comparison, she said. We establish the genetic profile and compare it.

She explained that DNA taken from crime scenes or on victims is stored long term in laboratory freezers.

In the case of Guylaine Potvin, many pieces were submitted to the laboratory at the time.

The same unknown male DNA, found in saliva and blood, was found on a box of condoms present at the crime scene. The genetic profile could be established from blood stains on the box.

In 2000, investigators had a few suspects in their sights, but none of them matched the DNA found in the room and on the body of Guylaine Potvin.

Following the identification of the Grenon surname thanks to the project PatronYme, investigators targeted Marc-André Grenon, whose name had appeared years earlier in the investigation into the murder of Guylaine Potvin. They obtained the right to collect without his knowledge a cup and two straws that he had left in the trash can of a cinema.

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Blood was found on this belt. The original photo was cropped.

Her genetic profile was thus established.

New analyzes were carried out from samples taken in 2000. Caroline Paquet took care to indicate to the jury that the original analyzes were valid, but that the techniques had evolved and that they sometimes made it possible to establish nuances in the results.

It is by comparing the genetic profile of Marc-André Grenon to that found on the victim's body and in his room that everything matched.

Caroline Paquet summarized that the DNA of Marc-André Grenon was found in the oral swabs, in the swabs from the genitals, under the nails of the right hand and the left hand of Guylaine Potvin. The accused's DNA was also found on the victim's t-shirt, in the area of ​​the left breast. It was also the blood of Marc-André Grenon which was found on the belt seized near the body of Guylaine Potvin and on a box of condoms found at the scene.

Teilor Stone

By Teilor Stone

Teilor Stone has been a reporter on the news desk since 2013. Before that she wrote about young adolescence and family dynamics for Styles and was the legal affairs correspondent for the Metro desk. Before joining Thesaxon , Teilor Stone worked as a staff writer at the Village Voice and a freelancer for Newsday, The Wall Street Journal, GQ and Mirabella. To get in touch, contact me through my teilor@nizhtimes.com 1-800-268-7116