A Canadian sergeant convicted of assaulting his former spouse three times has been handed a conditional discharge by an Ontario judge who noted a “link between his service-related concussions and the mental health deterioration” the soldier experienced from deploying to Iraq five times and Afghanistan thrice.
Mark MacChesney who served as a member of JTF2, an elite special forces unit, was found guilty in the Ontario Court of Justice last fall of assaulting his ex-wife Malory Seaboyer in August 2020, September 2022 and November 2022. The same judge also found the 41-year-old soldier guilty of mischief for damaging a wall in their matrimonial home.
“His character, and public service are both mitigating factors on sentence. But I find that they also bear on his moral responsibility. On the evidence and material before me, I find that the effects of Mr. MacChesney’s concussions and PTSD from combat in (the Canadian Armed Forces) lessen his moral responsibility,” Justice David Rose wrote in a recent decision.
“While I am often asked to consider concussions or PTSD in the context of a sentencing, this is the first time in my judicial career that I have been asked to make that finding in the context of a Canadian combat soldier. In my finding his moral responsibility is lessened.”
Seaboyer “testified to having a volatile marriage,” Rose said in his March 5 reasons for judgment.
“She said the marriage was fraught and the level of tumult in the home was uncertain on a day-to-day basis.”
MacChesney did not have a lawyer for his trial and did not call a defence.
Seaboyer described an Aug. 1, 2020 fight between them where MacChesney “wanted her to leave the room,” said the decision. “He pulled her off the bed with her wrists. He then climbed on top of her and brought his elbow across her neck, leaving scratches to her neck.”
During a Sept. 13, 2022, incident, “MacChesney threw a pillow at her, which landed outside the bedroom,” said the decision, which notes that when she “went to retrieve it,” their bedroom door was locked.
“She got a key to the door from elsewhere in the house and unlocked it to find Mr. MacChesney standing in the doorway. He refused to let her in,” said the decision. “Mr. MacChesney spat on her and grabbed her bottom lip. He grabbed her by the hair and pulled her down to the floor.”
After returning from undergoing a medical procedure at the local hospital on Nov. 14, 2022, Seaboyer “lay in her bed to recover,” said the decision. “Mr. MacChesney entered the room, kicked the wall. Ms. Seaboyer left the room and when she reached the front door he grabbed her by the shirt and ripped it. He then shoved her backward. She went back to her bedroom to lay down, when Mr. MacChesney entered the room and threw an egg at her hitting the wall. He then cleaned up the mess and shoved it in her face. He told her that he was ‘putting the garbage where the garbage belongs.’”
Beyond the specific offences MacChesney was convicted of, Seaboyer “spoke of walking on eggshells throughout the marriage to avoid outbursts,” said the decision.
“She suffered physical, psychological and emotional abuse which eroded her confidence and stripped her of her self-worth. She suffered from a disruption to her eating and sleeping habits. As she said…. ‘the damage is deep and enduring.’”
MacChesney has served nearly two decades in the Canadian military.
“Notably in 2009 he joined Special Forces and became an active duty member in 2011,” said the decision. “He was deployed to Iraq five times, and Afghanistan three times between 2011 and 2023. In 2025 he became an infantry instructor and has been on medical limitation work since July 2025.”
MacChesney told the author of his pre-sentence report “that he is no longer capable of serving in the military because of physical and mental health issues. He sustained several injuries during the course of his service, including multiple concussions, a shoulder and neck injury. He self-reports to (post-traumatic stress disorder) and anxiety.”
According to the judge, “it would appear that he is having trouble with the divorce process and being unable to see his children.”
MacChesney’s father “believes his son has PTSD from his military service,” said the decision. “Notably, he said that, ‘when his son returned from deployment, he noticed he was more distant than usual,’ and ‘… his son should have been given more time between deployments to readapt to normal life.’”
A Special Forces colleague, Adam Holmes, a Medal of Valour recipient, “referred to serving in theater with Mr. MacChesney. He said, with purposeful vagueness, ‘On another operation we observed enemy combatants attempting to maneuver and engage a friendly force from another nation. Mark quickly assessed the situation and expediently decided how to appropriately deal with the immediate danger presented before us. He utilized every member of our team to quickly determine the best means of interventions…. His actions prevented the loss of life or injury to the forces of another nation.”
MacChesney “has received six Military Honours for his service in combat,” said the judge.
Rose provided an academic article about “Military-related traumatic brain injury and neurodegeneration” to the lawyers handling MacChesney’s case.
“It is research-based guidance on some of the observed effects of combat on the cognitive function of soldiers by two academics from two reputable institutions,” said the judge.
The study’s “authors conclude that ‘it has been increasingly recognized that there is a frequent association of mTBI (mild traumatic brain injury) and PTSD in modern warfare,” Rose said.
“It would appear that the only way of physically confirming the nature of the brain injury is from a post-mortem examination. Each of the study participants appears to have died by suicide, violent death or a brain hemorrhage.”
The Crown argued there’s “no evidence of TBI or PTSD on the part of Mr. MacChesney.”
Rose disagreed. “As the collateral sources at sentencing provide, Mr. MacChesney has suffered verifiable concussions from his service. He fell out of a helicopter, suffered a parachuting accident, and fell off a motorcycle in training. His concussions from known accidents in service are documented. In addition, his father’s words that he became ‘more distant’ after his tours of duty, and that his deployments were too rapid are to be given real weight.”
A military doctor who diagnosed MacChesney in 2018 with “multiple brain concussions and mTBI mild to moderate are also to be given real weight.”
On top of that “is that Mr. MacChesney’s service for CF involved infantryman combat and all that comes with it,” said the judge.
“He was the tip of the spear in service of the Canadian Government’s kinetic foreign policy. It is an inference that he was exposed to explosive blast of one form or another during his service, although there is no mention of that in the evidence. As a member of JTF2 the full narrative of his time in uniform is not publicly available to a civilian court such as this.”
MacChesney took “psychotherapy from August of 2023 to September of 2025 with complaints of low mood, energy and sleep,” said the decision.
He’s also taken more recent “counselling through his army base from June of 2025 up to January of 2026,” said the decision.
According to a lawyer who reviewed his file, the “collateral consequences” of a conviction for MacChesney would likely be termination “from the CF with a compulsory release,” said the decision.
The “collateral consequences to Mr. MacChesney are not simply monetary,” said the judge.
“Having served in the CF for nearly 20 years in a high-risk role a conviction would seriously risk him being released into civilian life with none of the necessary support to make that transition. His service to Canada would amount to very little going forward. Beyond that, releasing a combat soldier to civilian life without support for that transition strikes me, at best, as contrary to the public interest.”
Aggravating factors in the case include “the level of humiliation in the encounters,” said the judge.
“In this case Mr. MacChesney called Ms. Seaboyer a ‘c–t,’ and wiped egg into her face; this is a case of intimate partner violence. Ms. Seaboyer is entitled to live in her house free of intimidation and violence.”
Her “input is vivid,” said the judge. “Ms. Seaboyer said that, ‘There were days I could not eat, nights I could not sleep, and many moments I genuinely feared for my life. Even now I carry the weight of what I endured.’”
MacChesney has separated from Seaboyer “and has no contact with his children,” said the judge. “I am told that the divorce and custody issues are before the Court in New Brunswick.”
MacChesney’s “character letters from his colleagues, family and neighbours are quite positive,” Rose said.
The Crown recommended MacChesney get a four-month conditional sentence.
“Given the many significant mitigating circumstances I find that a custodial sentence, even one on the community, is unnecessary,” said the judge.
“While Ms. Seaboyer suffered from psychological injury, a bruised lip, and a scratch on her neck, the level of physical injury and passage of time since the assaults combine to minimize the need for a custodial sentence to serve the denunciatory and deterrent requirements of this sentence.”
Rose came “to the conclusion that, in the unusual factors of this case, Mr. MacChesney should be discharged” after completing 18 months of probation.
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