A respected police sergeant who "maliciously" punched a man on the skull as he was recovering from a head injury will spend the next 10 months behind bars.
Thom Wing-hong, 49, was convicted of grievous bodily harm after losing control at Yau Ma Tei police station in May last year.
A month before the incident, victim Lik Sin-wan, 37, had undergone head surgery.
Kowloon City magistrate Peter Law Tak-chuen yesterday told the disgraced officer the act of striking someone obviously recovering from a head operation was "scary."
Law, while also blasting Thom for trying to obstruct justice, said: "Such a malicious act [the punch] should only happen in the movies or in the dark ages of the last century, not inside a police station of modern day, civilized Hong Kong."
The sergeant was told he had abused his power, destroyed people's trust in the police and eroded years of dedicated work.
The assault only came to light after another magistrate noted Lik's injury in a court appearance and ordered a police investigation.
On May 11 last year, Lik was stopped and searched on Shanghai Street. He was taken to the station and asked to remove his clothes for a body cavity search.
Lik demanded the search be conducted at a hospital and got into an argument with Thom and another officer.
The sergeant then punched Lik in the head, opening a wound and causing it to bleed.
Thom then accused Lik of assaulting a police officer. Lik appeared in court in August last year but was acquitted.
The magistrate's order for a police investigation into Lik's injury led to Thom being charged. Lik's request was reasonable and not intimidatory, Law said, yet Thom had found it offensive and assaulted him.
It was a serious breach of the confidence the public has in the police.
In mitigation, a letter signed by 196 officers from the Kowloon West emergency unit, to which the sergeant was attached, and another from Thom's wife were submitted.
The defense said Thom committed the offense during a momentary loss of control and it was not his normal behavior.
The incident ruined his career and cost him his pension.
Law said he understood Thom had dedicated much of his life to the police force and that he was praised by his superiors for his outstanding performance and was well liked by colleagues.
His years of hard work have vanished into thin air at a time when he is reaching retirement, Law said.
"I've been a magistrate for more than a decade, this is one of the most difficult cases to sentence. I see the difficulties the defendant is going through, but as a magistrate I need to make a decision for sake of the victim, society and justice."
Although Lik's injuries were not permanent, the magistrate said a jail term for Thom was inevitable. He used a starting point of 12 months' jail with two months off for Thom's contributions to the police force.
The defense applied for bail pending an appeal, but this was rejected.