Murder of Guylaine Potvin | “She didn’t get up, it wasn’t her habit”

Audrey St-Pierre, a friend, but also the last person to see Guylaine Potvin alive, described the vision of horror she had when discovering the young woman’s lifeless body in her apartment in Jonquière in 2000.

On the first day of the trial of Marc-André Grenon, accused of murder and sexual assault, she delivered an emotional testimony which brought tears to the eyes of the many members of Guylaine Potvin’s family who are following the proceedings at the Chicoutimi courthouse.

Like Guylaine Potvin, Audrey St-Pierre is originally from the Lac-Saint-Jean region and was studying at the CEGEP de Jonquière in specialized education technology at the time. The two young women saw each other regularly, to the point where they called each other every morning “to talk about it”.

“We came from approximately the same area. We were very different, but complementary. We confided in each other a lot,” Audrey St-Pierre testified to the jury.

The evening before the crime, the two young women had worked until late to finalize work that they were to present the next day. However, on April 28, 2000, in the morning, Guylaine Potvin did not answer the phone.

“She didn’t get up, it wasn’t her habit,” recalled Audrey St-Pierre, panicked at the idea of ​​arriving late for the presentation of the work.

She therefore goes to Guylaine Potvin in the hope that the young woman has simply forgotten to wake up. But upon entering the apartment, she discovers her room upside down.

Audrey St-Pierre quickly noticed that something was wrong. First, Guylaine Potvin is on her back, in her bed, naked, “which is not her style”.

“We saw all his parts. She was lying down, her face was blue, her hands had like marks,” she described, shedding a few tears.

A “suspicious” presence

Arriving on site, the police quickly concluded that there was a “suspicious presence” on the scene at the time, the prosecutor responsible for the case, M.^e Pierre-Alexandre Bernard, in his opening statement.

Since “a crime scene means a lot,” a forensic identification technician is called to the scene. A belt and a box of condoms were seized and the body of Guylaine Potvin was sent to Montreal for an autopsy.

A “biological analysis” will allow us to conclude that another individual was present on the scene at the time of the crime, a man. “But the DNA profile alone does not formally identify someone. It takes a comparison,” described M^e Bernard, addressing the jurors.

However, there are no direct witnesses to the crime. Several avenues are explored, but the investigation stalls. “The file remains open. Several suspects will be eliminated from the list of suspects, little by little, but it is clear that the days, months, years pass without us being able to match the DNA found on the scene,” underlined Mr.^e Bernard.

Innovative technology

Until the entry on the scene, in June 2022, of the Laboratory of Judicial Sciences and Legal Medicine (LSJML). The government organization, which brings together experts from several disciplines, then suggests to the investigators responsible for the file that they add it to what is designated as the “PatronYme project”.

This recently developed technology focuses on the Y chromosome, a component of DNA that only men have. It consists of drawing from large DNA banks to which the LSJML has access to associate a genetic profile with a family name.

“This chromosome [Y]it comes to us from our father who received it from his own father. […] From father to son, there is transmission of this chromosome,” detailed the Crown prosecutor. “Another thing also which, in customs, in Western social conventions, is transmitted from father to son: it is the family name. »

That of Marc-André Grenon then emerges and is judged to be “priority” in the investigation.

A spinning is authorized at its location, during which a cup and two straws will be recovered “legally”, took care to specify M^e Bernard. The suspect’s DNA collected from these items is compared to that found at the Jonquière crime scene. It agrees.

With this information in mind, the police obtained a warrant to arrest Marc-André Grenon and take a DNA sample from him. Once again, the DNA matched that found on the belt and the condom box.

On October 12, 2022, Marc-André Grenon was arrested. Twenty-two years after the murder of Guylaine Potvin. “It is sometimes said that justice moves slowly, but what we can certainly say is that it has a long arm,” M seriously told the jurors^e Bernard, in conclusion.