Const. Daniel Montsion used far more force than a "reasonable" officer would have when he assisted in the 2016 arrest of Abdirahman Abdi, making him criminally responsible for the man's death, the Crown has argued.

Crown attorneys have submitted written final arguments in the case of the Ottawa Police Service officer, who has been charged with manslaughter, aggravated assault and assault with a weapon in the death of the 37-year-old Abdi.

Montsion punched Abdi in the head several times during the arrest while wearing gloves with reinforced knuckles. Abdi lost vital signs not long after, and was declared dead in hospital the next day.

But the evidence in the case is complex, considering that Abdi had a pre-existing heart condition and that he ultimately died of a heart attack.

The Crown suggests the punches, delivered "less than a minute" after Montsion arrived on scene, were a significant factor in Abdi's death, breaking bones in his face and causing severe brain damage.

"[Montsion's] conduct demonstrated a wanton or reckless disregard for Mr. Abdi's life and safety, and was a marked and substantial departure from the standard of care of a reasonably prudent, similarly situated police officer," the attorneys write.

Abdi lost vital signs outside of his Hintonburg apartment building on July 24, 2016, after a violent confrontation with police. He died in hospital the next day. (Court exhibit)

Lethal force is only justified when the officer believes that someone will suffer grievous bodily harm, they argue.

Montsion's defence lawyers have received the arguments and will have time to respond in writing before an April 27 court date.

Typically the defence would make their arguments first, but the judge switched the order after the defence said the Crown's "theory of liability remains unclear, particularly on excessive force."

Key questions

According to the Crown, Montsion punched Abdi eight times in the head and face while wearing gloves with reinforced, "plated" knuckles — five times while both were standing, and three more while Abdi was face down on the ground.

They say the case turns on a few key questions: whether Montsion assaulted Abdi with or without a weapon, and whether he caused Abdi's facial injuries and death. If the Crown can prove he did, the judge then must ask whether Montsion was justified.

The Crown argues that by the time Montsion arrived on scene, Abdi was unarmed, had no reasonable escape route, and wasn't showing signs of violent behaviour.

While Montsion may have heard alarming details over his police radio while en route, the Crown says he used excessive force for the actual situation he was confronted with.

"[Montsion] had to know [the] damage that just one punch with his hard knuckle-plated gloves would do to a person's face. He had to know it would cause grievous bodily harm, or at least foreseen the risk of causing bodily harm that was neither trivial nor transitory," the attorneys write.

A longer version of the video secured as digital evidence in the trial of Const. Daniel Montsion. It appears to show Abdirahman Abdi being kicked and punched by police officers in front of the apartment building at 55 Hilda St. 5:51

Refuting defence theories

Throughout the trial, Montsion's defence lawyers relied on two key theories to prove the officer's innocence.

They said that Abdi, who was arrested for assaulting women outside a Bridgehead coffee shop, was showing signs of excited delirium — a condition associated with erratic and potentially dangerous symptoms.

They also suggested it was the other officer on scene, Const. Dave Weir, who broke the bones in Abdi's face when he pushed him to the ground.

At one point, Weir told the court he felt Abdi possessed "super-human strength" and credited Montsion with saving his life.

The Crown has called that testimony "embellished and exaggerated," arguing it wasn't borne out by what other witnesses described or what was caught on surveillance video.

Police were called after a disturbance involving Abdirahman Abdi at the Bridgehead coffee shop on Wellington Street W. The Crown asserts he was not dangerous. (Supplied)

In their written arguments, the Crown concedes Abdi was involved in "assaultive behaviour," that his arrest was justified and that he wasn't taking the medication prescribed to him for a mental health issue.

But they say Abdi wasn't malicious, violent or dangerous.

"A fairer characterization of Mr. Abdi on July 24, 2016, is that of a slow, awkward and at times unwelcome nuisance," the Crown attorneys write.