Quebec cold case murder trial: Prosecutors complete evidence, defence granted delay

SAGUENAY, Que. — Crown prosecutors completed their case Friday against a Quebec man charged with the first-degree murder and sexual assault of 19-year-old junior college student Guylaine Potvin nearly 24 years ago.

Prosecutor Pierre-Alexandre Bernard told jurors the Crown completed presenting evidence in the case of Marc-André Grenon, 49, after testimony from forensic biologist Caroline Paquet. 

Quebec Superior Court Justice François Huot then granted a delay to Grenon’s lawyers, who will announce Monday whether they will present a defence.

Huot told jurors they would either hear witnesses starting Monday morning or be sent home while lawyers debate legal points ahead of final arguments later in the week.

The trial heard that officers arrested the accused in October 2022 after a research tool used by the province’s forensics lab suggested the previously unidentified DNA from the crime scene might be connected to the last name Grenon.

Paquet testified that DNA samples obtained in August 2022 from two drinking straws Grenon had discarded at a movie theatre matched evidence taken from several places at the crime scene, including under Potvin’s fingernails, on a T-shirt she was wearing and on a box of condoms.

Potvin was found dead in April 2000 in her apartment in Jonquière, now part of Saguenay, Que., some 215 kilometres north of Quebec City. A pathologist testified that the teenager had died of strangulation, with injuries that included blunt trauma to her head and shoulder, a bite mark on her left breast, and injuries to her genital area.

While male DNA was discovered at the crime scene, there was no match in the police database, no witnesses to the crime, and — for more than 20 years — no arrests.

Paquet, who was called as an expert witness, read Wednesday from a report that concluded it was “hundreds of billions of times more probable that the male DNA taken from under the nails of (the victim’s) right hand come from Marc-André Grenon rather than from someone else.”

Grenon has pleaded not guilty.

The trial heard that Grenon’s name had surfaced in the investigation’s early years; he became a prime suspect after a project tracking Y chromosomes — which are passed down from father to son — first suggested the crime scene DNA might be connected to someone with his last name.

This report by The Canadian Press was first published Feb. 2, 2024.

— By Sidhartha Banerjee in Montreal, with files from Morgan Lowrie.

The Canadian Press

Note to readers: This is a corrected story. A previous version had the wrong year for when DNA samples were collected at the crime scene.