Without even knowing the suspects in the Guylaine Potvin murder case, a forensic biologist was able to identify the precise last name of the man who was accused of the crime, 22 years after the facts, thanks to a genetic analysis technique innovative.
This expert at the Laboratory of Judicial Sciences and Legal Medicine (LSJML), Valérie Clermont-Beaudoin, came to testify on Tuesday, at the start of the third week of the trial of Marc-André Grenon, at the Chicoutimi courthouse.
The man is accused of having sexually assaulted and killed Guylaine Potvin on April 28, 2000, in Jonquière, Saguenay–Lac-Saint-Jean, a case which caused a lot of noise at the time in the region. Arrested in 2022, more than 20 years after the events, he pleaded not guilty.
PHOTO PROVIDED BY THE SÛRETÉ DU QUÉBEC, VIA THE CANADIAN PRESS
The victim, Guylaine Potvin
The use of an innovative genetic analysis technique called the “patrYme project” is at the heart of the procedures.
Recently developed, this technique focuses on the Y chromosome, a component of DNA that only men possess and which is passed from father to son in such a way that, traditionally, it is also associated with family names.
DNA under the victim’s nails
Thanks to DNA found at a crime scene, the LSJML can establish the “Y profile” of a suspect and compare it to a database that it itself created and entitled “pYste” where several profiles are associated with family names.
As part of the investigation into the murder of Guylaine Potvin, the suspect’s “Y profile” was established using DNA found under the nails of the young woman’s right hand, detailed Valérie Clermont-Beaudoin.
Entered into the “pYste” database, this profile made it possible to establish several matches, the most precise of which was with the surname “Grenon”. “The match was the one with the highest score,” explained Valérie Clermont-Beaudoin. There were no differences observed between alleles [des fragments d’ADN] of the two profiles observed. »
PHOTO PROVIDED BY THE SÛRETÉ DU QUÉBEC, VIA THE CANADIAN PRESS
The accused, Marc-André Grenon
This discovery, in the summer of 2022, was then transmitted to investigators who were able to begin tracking the suspect, Marc-André Grenon, from his home in Granby to a movie theater.
At the end of this operation, agents of the Sûreté du Québec were able to recover two straws and a glass on which a DNA sample collected made it possible to establish a match with the DNA found on the scene at the time. Marc-André Grenon was finally arrested in October 2022.
More details to come.