The offence of hindering a police officer who is in the course of doing his duty (Police Act 1996 s 89). “Obstruction” includes any intentional interference, e.g. by physical force, threats, telling lies or giving misleading information, refusing to cooperate in removing an obstruction, or warning a person who has committed a crime so that he can escape detection (e.g. warning a speeding driver that there is a police trap ahead). It is not, however, an offence merely not to answer, or to advise someone not to answer, police questions that he does not have to answer. A police officer is acting in the course of his duty if he is preventing or detecting crime (in particular, breaches of the peace) or obeying the orders of his superiors. However, he is not acting in the course of his duty when he is merely assisting the public in some way unconnected with crime. When the obstruction amounts to an assault, the offence is punishable by imprisonment and/or a fine. One may be guilty of this offence even if the police officer was in plain clothes.