A 23-year-old man has been acquitted of taking part in an unlawful assembly and two related charges during a 2019 protest after a Hong Kong magistrate found the arresting officer’s version of events “inherently impossible”.

Kwun Tong Court held on Thursday that the police constable who detained defendant Yuen Tsz-to had offered a contradictory account of the drama that unfolded outside Hsin Kuang Centre in Wong Tai Sin on October 7, 2019.

But the presiding magistrate found Form Six student Mak Wing-wa, 17, who stood trial alongside the unemployed Yuen, guilty of unlawful assembly after ruling the teenager had deliberately shone bright lights at a police cordon in a challenge to officers and to impede their operation.

The Wong Tai Sin protest was staged two days after the government bypassed the city’s legislature to ban the wearing of masks at all public assemblies by invoking a colonial-era emergency law.

The trial last month heard that before the illegal gathering, masked protesters had barricaded Lung Cheung Road, a major thoroughfare in eastern Kowloon, but the blockade was already cleared by the time the two accused arrived at the scene.

Police officers who testified in court described a stand-off on a footbridge outside Hsin Kuang Centre at 10pm, after a senior inspector’s decision to close off the bridge and instruct residents to use another crossing 240 meters away raised the ire of locals.

Constable Fong Yiu, who arrested Yuen that night, accused the defendant of pushing him during a chase. He said he then lost track of Yuen, but later recognised him among a group of 14 detainees and found two spanners in his backpack.

In his police notebook and three court statements, Fong said Yuen had worn a mask at the scene. However, he claimed in the witness box to have seen the man’s entire face that night.

The officer added that Yuen had attempted to flee by running onto Lung Cheung Road, even though the flow of traffic had resumed, in what the constable described as a suicidal act.

Yuen Tsz-to was cleared on Thursday at Kwun Tong Court.

In Thursday’s verdict, Magistrate Andrew Mok Tze-chung found it unlikely for Yuen to have picked such a treacherous escape route, and even less probable for Fong to have given chase in the middle of moving traffic.

The magistrate also found it absurd for the officer to arrest Yuen on suspicion of possessing unlawful instruments before he could inspect the defendant’s belongings.

“The police constable’s evidence was seriously contradictory and his account was inherently impossible. I refuse to take his evidence into account,” Mok said.

He cleared Yuen of unlawful assembly, resisting a police officer and possessing articles with intent to damage property.

But the magistrate accepted most parts of the remaining police evidence as true, and held that Mak, the other defendant, had indeed shone bright lights at officers alongside three other protesters.

He ordered the teen to be remanded in custody pending assessment reports, ahead of sentencing at Eastern Court on September 2.