HONG KONG (Reuters) - A former senior Hong Kong police officer was sentenced to three months jail on Wednesday for assaulting a passerby with his baton during the city’s massive pro-democracy protests of late 2014.

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The “Umbrella Movement” demonstrations which occupied major roads and demanded, in vain, full democracy for the former British colony, was one of the most direct populist challenges to Beijing’s Communist Party leaders since the city came under Chinese rule in 1997.

During the civil disobedience movement that ran for 79 straight days, protesters, sometimes numbering in their thousands, faced off repeatedly with the police who used batons, tear gas and pepper spray -- drawing some criticism for the excessive use of force.

Retired superintendent Frankly Chu, 58, showed no obvious emotion when principal magistrate Bina Chainrai sentenced him to four months jail for assault occasioning actual bodily harm.

This was mitigated to three months given his retirement and the unlikelihood of him reoffending.

Chainrai said the sentence was necessary so that public confidence in the police force could be maintained and that the police had a “duty to uphold standards”.

Chu was filmed hitting a man on the neck with a baton during a protest in the Mong Kok district in 2014, targeting what some deemed to be a high-risk part of the body.

Chu, however, said during the trial that his use of force had been appropriate and that he was carrying out orders from his superiors to move protesters away from that area.

Chu’s lawyer, Peter Pannu, said his client would appeal.

A Hong Kong court last February also sentenced seven policemen to two years behind bars for beating a handcuffed activist during the 2014 protests. The seven have been released on bail pending appeal.

The assaults by the seven policemen, and Chu, were captured on video and widely broadcast, triggering public outrage and tarnishing the reputation of the Hong Kong police force that has sometimes been dubbed “Asia’s finest”.

Police support groups, however, say the officers were only maintaining public order. After the sentencing, around 30 supporters of Chu yelled: “Hong Kong’s judiciary is unfair. Hong Kong police were insulted”.

A University of Hong Kong poll that surveyed over a thousand people shows public satisfaction with the police force’s performance after the Occupy protests were cleared in December 2014 plummeted to the lowest point since the handover right.

The half yearly figure has since risen from 21 percent in the first six months of 2015 to 37 percent in the last six months.