The trial of an officer acquitted of assaulting a 12-year-old boy could have ended differently were it not for what legal experts call "textbook" and "crucial" procedural missteps made by the Crown and possibly even investigators.

On Wednesday, provincial court judge Ryan Rolston cleared Winnipeg police Const. Christian Guyot of assaulting the boy, now 13, on Aug. 7, 2017.

The Independent Investigation Unit, which investigates all serious cases involving Manitoba police, charged Guyot in November 2017 after video surfaced appearing to show a uniformed officer smacking the boy.

Court heard the boy's mother called police that day when her son, in the middle of a temper tantrum, began throwing things around and damaging the home. The video shows the boy swearing at a male officer (a female officer was also present) who then raises his arm and swings it out of frame and toward the boy.

A loud slap is heard, followed by a wincing sound from the boy and the male officer saying "show some f--king respect."

Crown attorney Kaley Tschetter failed to prove beyond a reasonable doubt the officer in the video — a bald man Judge Rolston agreed resembled Guyot — was in fact Guyot.

Professors in the law faculties at the universities of Calgary and Manitoba, and a spokesperson for the Criminal Defence Lawyers Association of Manitoba, scrutinized Tschetter's handling of the case, Rolston's decision, as well as the IIU's role in investigating.

They all suggested Rolston's decision was reasonable given what was presented, and that the Crown could have called more evidence.

Tschetter didn't call Guyot's partner to testify, nor did she table his officer's notes or call records from Aug. 7, 2017. Also, no evidence was presented at trial that could put Guyot in the boy's home that day or, at minimum, confirm he is even a member of the Winnipeg Police Service.

Missing link

Richard Jochelson, an associate professor in the faculty of law at the University of Manitoba, said the Crown had to take extra steps to link the person in the video to the person in court and the WPS.

"This is a case where that omission essentially resulted in an acquittal and it just demonstrates, I think in a profound way, that even in cases that seem obvious, that seem extremely linear — person "A" hits person "B," person "B" suffers some sort of harm, typical assault, for example — it's still the Crown's responsibility to prove beyond a reasonable doubt the identity of the accused," said Jochelson, an expert on criminal law and police powers.​

"This is in some ways a textbook case of how important that is and what happens if you don't manage to do that."

Tschetter did not respond to a CBC News request after the trial asking her to clarify why the Crown didn't provide further evidence identifying Guyot.

A Manitoba Justice spokesperson said only that Crown attorneys build a case based on what evidence they expect will be heard from witnesses at trial.

"Much can happen in a trial and for any number of reasons what is expected does not always occur," the spokesperson wrote in an email.

Witness testimony falls through

When the boy and his mother failed to appear in court, Tschetter's case rested on the video evidence and testimony from only the boy's sister, who filmed the incident but could not confidently identify Guyot in court on Wednesday.

Guyot, one of several bald or balding men in the courtroom that day, was seated behind and to her right.

"I think the video quite clearly shows Mr. Guyot," Tschetter told Rolston before the decision. "I would suggest this is enough."

It wasn't enough. Rolston admitted the officer in the video showed a "shocking degree of lack of self control" and could be Guyot, but he couldn't be sure beyond a reasonable doubt based on the one brief view of the officer's face in the at-times shaky video.

Watch the raw video reviewed at the trial (WARNING: contains offensive language):

This video sent to CBC by family shows a Winnipeg police officer allegedly slapping a 12-year-old boy after the teen swears at the officer. The officer will be charged with assault, according to Manitoba's police watchdog. 1:12

"The video didn't speak for itself, in other words," said Jochelson.

"The video in this case was ambiguous enough that the foundation for who was in it had to be established and that link was never made."

'Omission' led to acquittal: law prof

Lisa Silver, a lawyer and associate professor at the University of Calgary, said in such a case having video evidence, and testimony from the person who shot it, isn't necessarily enough to "connect the dots" on the identity of the accused.

"As an armchair look at this, there is more evidence that could've been called," said Silver, an expert in evidence, criminal law and advocacy.

She said it is "crucial" that the identity of an accused person be established beyond a reasonable doubt, just like any other element of a case.

Apart from call records or the officer's personal notes, one option that could've been at Tschetter's disposal was to have a forensic video expert testify to the likelihood of the person in the video being Guyot, she said.

"They could hear an expert and not be satisfied, but for God sakes I would call that evidence. You know, what's the worst that would happen, the judge says it's not admissible?"

IIU role

The IIU has investigated about 100 cases involving Manitoba police since the organization formed in 2015, including this one. It charged eight officers involved in seven of those cases.

In general, the IIU confirms the identity of an accused in a variety of ways, including eyewitness accounts, self-admission and circumstantial evidence, a spokesperson said.

Standard protocol in all cases is that Manitoba police organizations self-report to IIU when a possible offence on the part of an officer has occurred. That's what happened in this case when Winnipeg police Chief Danny Smyth alerted IIU director Zane Tessler to the existence of a video.

Tessler reviewed the evidence and found there was a "reasonable and probable grounds to believe a criminal offence occurred," resulting in the assault charge being laid against Guyot.

Witness problems ID'ing officer

Scott Newman, a Winnipeg defence lawyer and spokesperson for the Criminal Defence Lawyers Association of Manitoba, said it's possible the IIU could have better anticipated identification would be an issue at trial.

"In court, in-dock identification can be quite sketchy at the best of times," he said. "That's why we use photo lineups outside of the court process as soon as possible after the offence to try and neutralize any bias that might exist."

Had the police watchdog shown the boy, his mother and sister a photo lineup of Guyot and others who resemble him in November when it launched the investigation, it's possible the sister would have at that time demonstrated an inability to confidently identify him in a lineup, said Newman.

At that point, other means of confirming the identity of the person in the video could have been pursued, for instance pulling GPS info from the attending officer's cruiser car or officer notebooks from the day of the possible offence, he said.

"In this case, I think the Crown was probably relying on the three witnesses that they had subpoenaed to say, 'Well yeah this person in court is the cop who assaulted me," he said.

"The preferable practice, and what might have actually made the big difference here, is if the investigators had done a photo-pack lineup at the time to nail down whether or not they had a strong identification at the time."

An IIU spokesperson would not confirm whether witnesses were shown a police photo lineup, but said all evidence gathered during the investigation was forwarded to Manitoba Prosecutions.

Parallels to previous officer trial

Guyot hired Lisa LaBossiere and Hymie Weinstein to represent him, the latter having successfully cleared police officers facing criminal charges in the past.

In February 2011, Weinstein and another lawyer had perjury charges against two Winnipeg policeman tossed.

Consts. Jess Zebrun and Peter O'Kane were accused of lying under oath at a 2006 preliminary trial for two accused of drug trafficking.

The pair was charged in 2008 following an internal WPS ​investigation stemming from a drug bust at the Fairmont Hotel 2½ years earlier.

The Crown alleged the officers learned drugs were in a suite by illegally entering it before obtaining a search warrant that led to a raid. Both pleaded not guilty.

As in the case involving Guyot, Weinstein and his co-counsel Sheldon Pinx argued the Crown failed to prove the identities of the officers in court, and the judge agreed.

Crown prosecutor Robert Tapper in part relied upon police notebooks and WPS business cards left at the hotel. Tapper maintained the cards and notebooks belonged to and incriminated O'Kane and Zebrun, but their lawyers successfully argued Tapper wasn't able to prove the notebooks belonged to their clients. They also said there were conflicting witness testimonies.

"If they pointed to him and said, 'Yes, that's Mr. O'Kane, yes, that's Const. Zebrun,' identification is proven. And every Crown, with respect, knows that. You've got to prove identification," Weinstein said after getting the case dismissed.

"Day 1 of Crown attorney school they taught you, 'prove identity, prove jurisdiction.'"

The decision was overturned in the Court of Appeal and a retrial was ordered. The retrial fizzled out after O'Kane died in November 2012.

'Hard to be too hard on a Crown'

Newman, Silver and Jochelson all empathized with the demands against the Crown in the Guyot case and how planned witness testimony was never heard.

"It's hard to be too hard on a Crown attorney, because sometimes you don't expect that your case is going to fall apart," said Newman.