3. Assaulting, resisting, obstructing a police officer (S.36(b) Offences against the Person Ordinance)
Any person who assaults, resists, or wilfully obstructs a police officer in due execution of duty, or any person acting his aid is liable to imprisonment for 2 years.
It is not necessary for the prosecution to prove the knowledge of the accused that the person assaulted was a police officer or the officer was in the execution of his duty. (R v Forbes and Webb (1865) 10 Cox 362). However, if the defendant had a genuine belief either that the victim was not a police officer or in the existence of circumstances which would mean the officer was not acting in the course of duty, the general principle relating to mens rea and mistake of fact should apply and the defendant’s liability should be judged on the basis of that belief. For example, genuine and reasonable belief that the victim was a thug and not a police officer, would be highly material in judging the reasonableness of resistance exerted and the degree of force falling within the liberty or justification of self-defence. (Kenlin v Gardiner  2 QB 510) (See Archbold 2019, 20-285)
“Assault” covers both actual physical contact and mere threats causing the target of such threat to fear that he will face immediate physical harm.
What amounts to wilful obstruction depends on the circumstances including what the person had done and how it was done, what the police officer was doing, and the effect of what the person had done on what the police officer was doing.
The person accused of wilfully obstructing a police officer must be aware that the police officer is discharging his duties and deliberately does an act to obstruct the discharge of those duties.
It does not cover conduct that might cause mere inconvenience to the police officer or require him to expend trifling additional effort. But the conduct does not need to make the police officer’s work substantially more difficult.
Private citizens have a moral duty or social duty to assist police officers but there will be situations where co-operation is not readily forthcoming such as exercising the right to silence, seeking clarification from the police officer as to what is the matter of concern or seeking clarification of what is expected or required of him, reasoning with the police officer and trying to persuade the police officer that there was a mistake, protecting or advising a relative or close friend who is being questioned by the police officer, having other more urgent matters to attend to for the time being etc.