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 .
The story so far
- Guylaine Potvin was sexually assaulted and then murdered in her apartment in Jonquière, Saguenay, in April 2000. A few months later, in the Sainte-Foy district of Quebec, a young 20-year-old woman was strangled and left for dead by her aggressor.
- More than 20 years after the events, last October, a 48-year-old man, Marc-André Grenon, was arrested at his home in Granby and accused of being the perpetrator of these crimes. He pleaded not guilty and his trial date has yet to be set.
- A media group, including The Press is a member, has taken steps in court to lift the secrecy of the details of the long-term investigation that led to this arrest.
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,” that police officers across North America have successfully closed unsolved cases. (cold boxes)) dating back several decades, the most famous of which is that of the “Golden State Killer”.
A series of court documents released in part this Sunday lifts the veil on the details of the police investigation worthy of a movie script that led to the arrest, in Granby, on October 12, of Marc-André Grenon.
It is a series of affidavits presented to a justice of the peace in order to obtain various warrants to, among other things, search the suspect’s home in the hope of finding objects that belonged 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 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.
A random analysis, a subject of interest
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 assault, 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 investigation has always been active, but it was its takeover, in 2018, by the disappearances and unresolved files division of the Sûreté du Québec (SQ) that led to major progress.
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 “BÉLIER project”, into what it designates as the “PatronYme project “.
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 might match.
PHOTO ARCHIVES THE DAILY
Guylaine Potvin was found dead in Jonquière in April 2000.
Among the “surnames of priority interest” which 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.
A second address
Except that a match thanks to the “PatronYme project” does not constitute evidence presentable in front of a judge. “The identification will have to be verified using the traditional method of DNA analysis, from a comparison sample obtained by warrant, voluntary donation or an abandoned substance from the identified suspect”, it is also specified. in affidavits.
In order to flesh out 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.
A detail that seems to have escaped the investigators so far then arises. At the time of the second attack, in Sainte-Foy, the address that Grenon gave to the Ministry was located only 450 meters from where the victim lived.
This revelation seems to breathe new life into the investigation and other investigative techniques are implemented from the beginning of August. A few weeks later, Grenon will be apprehended at his home in Granby.
The authorities believe that Marc-André Grenon could have made other “minor or adult” victims. A serial crime investigation unit was deployed the day after his arrest last October.
The date of his trial has not yet been set.
Learn more
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- Number of subjects targeted within the framework of the investigation who could be eliminated thanks to the DNA
SOURCE: Quebec security