An expert in use of force with the Halifax Regional Police says Const. Matthew MacGillivray's behaviour during a traffic stop was both unreasonable and unnecessary.

But during the second day of testimony at Police Review Board hearing, MacGillivray's lawyer suggested the former sergeant was following proper police procedure to protect himself from potential harm.

Const. MacGillivray was demoted from sergeant as a result of how he handled the traffic stop on Highway 102 on Sept. 9, 2015.

Const. Matt MacGillivray's actions were a "marked departure" from police standards, the review board heard. (Jack Julian/CBC)

Angela Acorn and her husband Graham Labonte of Belle River, P.E.I., were travelling to Fall River, N.S., because Acorn had an appointment with a pain specialist.

In testimony before the Police Review Board they reported seeing then-sergeant MacGillivray swerving between lanes and at one point nearly hitting a highway median.

They followed him for several minutes and eventually passed him at 115 km/h in a 100 km/h zone.

Graham Labonte was on the stand Tuesday to talk about exact location of arrest at roadside on Highway 102. (Jack Julian/CBC)

MacGillivray pulled them over and a confrontation ensued.

When Acorn got out the vehicle, MacGillivray restrained and handcuffed her.

When Labonte got out of the car and started recording the scene with his smartphone, MacGillivray unbuttoned the retention flap on the top of his handgun holster.

A Halifax police officer is appealing his demotion over his use of force during an arrest a year ago. 0:40

On Tuesday at the hearing, Halifax Regional Police Insp. Lindsay Hernden called those actions "unreasonable" and "unnecessary." Hernden is an expert in police training in use of force.

He says Labonte's willingness to pull over for MacGillivray shows the couple was being compliant.

He testified MacGillivray's actions was a "marked departure" from police standards.

"The reasonableness of his actions is in question," Hernden said.

Halifax Regional Police inspector Lindsay Hernden is in charge of 110 patrol officers and is an expert in use of force. (Jack Julian/CBC)

Brian Bailey, the lawyer for MacGillivray, questioned Hernden about training manuals that describe traffic stops as situations of "unknown risk," emphasizing a need for vigilance and the motto "Complacency Kills."

Bailey also pointed out that Halifax police policy defines any movement toward an arresting officer as "active resistance."

Acorn and Labonte have filed a civil lawsuit against Halifax Regional Police at Nova Scotia Supreme Court.

The CBC's Jack Julian live blogged the hearing, which is scheduled to continue to Friday.