Crown prosecutors have filed an appeal to overturn a rare post-verdict mistrial declared last month in Frank Stronach’s sexual assault conviction.

The mistrial relates to a sexual assault charge involving someone who had worked at a business Stronach owned and who filed a civil complaint that was “at odds” with the evidence given in court, court documents detail.

The billionaire businessman was found guilty in June of sexual assault and the historical offence of indecent assault related to separate allegations brought by two of the women in his Toronto trial.

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The mistrial on the sexual assault conviction was granted weeks later by Superior Court Justice Anne Molloy. In an interview, lawyer Leora Shemesh called the decision to declare a mistrial after a conviction “incredibly rare.”

Crown prosecutors said in their notice of appeal that Molloy “erred by setting aside the verdict of guilt and declaring a mistrial based on inadmissible evidence.”

Initially, Peel Regional Police charged Stronach in 2024 with 18 offences involving 12 complainants. Those charges were split into two trials and related to allegations of sexual assault spanning the 1970s, ’80s and ’90s.

After a complicated trial where some charges were withdrawn, Stronach was found guilty of one count of sexual assault and one count of indecent assault. He was found not guilty of the rest.

He is set to be sentenced on the indecent assault conviction in September.

Stronach will also face trial on other charges in Newmarket, Ont., next year.

— with files from Isaac Callan