A technology resulting from advances in DNA analysis and whose use would be unprecedented in Quebec is the source of the arrest of Marc-André Grenon for the murder of Guylaine Potvin, which occurred more than 20 years ago .
This technology called PatronYme, and on which few details have been published so far, consists of a database compiled from various sources, including websites specializing in genealogy, and called “pYste”.
It’s akin to an innovative investigative technique, known as “genealogical genetics,” through which police officers in North America have managed to close unsolved cases (cold cases) dating back decades, including the most famous is that of the “Golden State Killer”.
It is a series of sworn statements (“affidavits”) presented to a justice of the peace in order to obtain various warrants to, among other things, search the suspect’s residence in the hope of finding objects belonging to his two alleged victims. The facts referred to therein have not yet been presented in evidence and could therefore be contested.
Marc-André Grenon is presumed innocent since he has not yet been tried for the crimes he is accused of, namely having sexually assaulted and then killed Guylaine Potvin, 19, on April 28, 2000, in Jonquière, Saguenay-Lac- Saint Jean.
He is also accused of sexually assaulting and leaving another 20-year-old woman for dead a few months later, in July, this time in the Sainte-Foy district of Quebec. This last victim survived and her identity is protected by a publication ban, for which it is not possible to name her.
These documents reveal that the man who has a long record of various minor crimes, most committed in the late 1990s, appeared on the radar of investigators at the very beginning of the investigation into the death of Guylaine Potvin, in particular because he had lived directly behind her home a few years before the murder.
Shortly after the second attack, in Sainte-Foy, the police had also concluded that they were the work of the same predator since DNA samples found at the two sites had turned out to belong to the same individual.
The main one comes in June 2022 when the Laboratory of Forensic Sciences and Forensic Medicine (LSJML) decides to integrate the investigation into the murder of Guylaine Potvin, entitled “project BÉLIER”, into what it refers to as the “Project PatronYme “.
This project consists of a list belonging to the LSJML and which contains tens of thousands of samples of Y chromosomes, a part of the DNA that only men have and to which is associated a family name, a data traditionally transmitted from father in son.
By incorporating DNA found at a crime scene, the database provides a list of surnames that the DNA profile could match.
Among the “surnames of priority interest” that emerge in 2022 in the investigation into the murder of Guylaine Potvin, that of Grenon is at the top of the list. It was then, in July 2022, that he became the “priority subject of interest” in the investigation.
Except that a match thanks to the “PatronYme project” does not constitute presentable evidence in front of a judge. “The identification will have to be verified by the traditional method of DNA analysis, from a comparison sample obtained by warrant, voluntary donation or an abandoned substance of the identified suspect”, specifies one moreover. in affidavits.
In order to expand their file, at the end of July, a sergeant-investigator from the SQ therefore contacted the Ministry of Labour, Employment and Social Solidarity in order to obtain the list of addresses given by Grenon to collect social assistance. She is long. Between 1993 and today, Grenon has changed his place of residence 59 times.
This revelation seems to breathe new life into the investigation and other investigative techniques are being implemented from the beginning of August. A few weeks later, Grenon will be apprehended at his home in Granby.
Authorities believe that Marc-André Grenon may have had other “minor or adult” victims. A serial crime investigation unit was deployed the day after his arrest last October.
His trial date has not yet been set.