A Halifax police officer who was demoted after a confrontation during a heated traffic stop has won his appeal and the complaint against him has been thrown out.

Matthew MacGillivray was a sergeant at the time of the September 2015 incident, but in January the Halifax Regional Police complaints commission demoted him to constable after finding he used excessive force, was discourteous and acted discreditably when arresting a P.E.I. couple driving to a medical appointment.

On Friday, the Nova Scotia Police Review Board overruled that decision and said the police officer acted appropriately and according to his training. The board dismissed the complaint filed by the couple.

"I have immediately reinstated Sgt. MacGillivray's rank," Deputy Chief Bill Moore said in a staff email obtained by CBC News.

Halifax police later confirmed MacGillivray will receive back pay for the difference between a constable's salary and a sergeant's salary.

At a hearing before the review board in September, MacGillivray's lawyer argued his client used reasonable and appropriate force given a potentially life-threatening situation.

Traffic stop quickly gets out of hand

On Sept. 9, 2015, Angela Acorn and Graham Labonte were driving from their home in Belle River, P.E.I., to a pain management appointment in Fall River, N.S.. They saw a police car, which they said was driving erratically.

Unlike the Halifax police complaints commission, the review board heard evidence from witnesses who were under oath and faced cross-examination.

The review board found the couple sped up to 115 km/h to pass the police vehicle. Acorn said she thought perhaps someone had stolen the police car and doubted if MacGillivray, who was in uniform in a marked car, was a real police officer. She said she gestured to him.

MacGillivray testified that he did not see any gesture. He also denied driving erratically. He said navigating the two roundabouts at the Larry Uteck Drive interchange may have given the impression of unusual driving.

'Exaggerated' evidence of rough arrest

On the highway, he drove in cruise control to measure the speed of other drivers. He stopped Labonte's car after it passed him to warn him he was speeding, the officer said. He got out and approached the vehicle, but Acorn got out the passenger side and approached him first.

MacGillivray twice told her to get back in the car. He warned her he would arrest her if she didn't get back into her car. She didn't, and he arrested her.

"The board finds that her evidence on the force of the arrest is considerably exaggerated and is not consistent with her own photographic evidence," the review board decision says.

'Calm and matter of fact'

MacGillivray called for backup. "The recorded call was played at the hearing; his voice is calm and matter of fact in that communication," the decision says.

Labonte then left the vehicle. The police officer told him to get back in it, but he didn't. Labonte shot video of the arrest, which showed he was moving toward the officer against orders. MacGillivray said Labonte approached with his chin down.

A screen grab from a video showing Matthew MacGillivray arresting Angela Acorn in September 2015. (Graham Labonte)

"He is considerably larger than Const. MacGillivray and it was reasonable for the officer to perceive this large, angry man as a serious threat," the decision says.

Labonte said, "I want to see your name." MacGillivray, who had earlier identified himself, threw his name tag toward Labonte.

Acorn 'clearly angry'

The video shows Acorn "clearly angry" and "struggling, very vocal, and using profanity towards Const. MacGillivray," the decision says.

MacGillivray eventually arrested both people. Other police officers soon arrived and got the situation under control. The couple were initially charged with failing to obey a police officer and failing to obey a traffic sign (the speed limit), but both charges were withdrawn without MacGillivray's knowledge.

"It is clear the arrest was lawful; Ms. Acorn, in refusing to return to her vehicle, was committing an offence," the board found.

"Her actions put her, and Const. MacGillivray, and other drivers on the highway at risk," it later says.

Video clip caught only part of incident

It also found the officer's use of force matched his training. "There can be no doubt that the conduct of Ms. Acorn, in advancing quickly towards Const. MacGillivray and the highway could cause bodily harm," it says.

In its decision, the board said it recognized "that the 20-second video produced by the complainants, and the 911 call, if seen and heard in isolation by the public, could readily leave the impression of discreditable conduct."

But, it says, "these items standing alone do not reflect the reality that a lawful arrest had been made, following on a reasonable perception that a real danger existed."

Mark Hartlen, president of the Halifax Regional Police Association, welcomed the ruling.

"This has been a very difficult time for Sgt. MacGillivray and his family and friends, and for the organization as a whole, and I commend him for continuing to provide quality service to the public during this challenging process," Hartlen wrote in a news release.