The requirement there is “reasonable cause to suspect” precedes the use of many police powers and provides validity to subsequent police action. When legislation requires "reasonable grounds" as a state of mind (including suspicion and belief), it requires facts ‘ sufficient to induce that state of mind in a reasonable person ’. In relation to a suspicion, ‘[t]he facts which can reasonably ground a suspicion may be quite insufficient reasonably to ground a belief, yet some factual basis for the suspicion must be shown’ [see George v Rockett [1990] 170 CLR 104at 112 and 115; [1990] HCA 26]. Suspicion is a state of mind which ‘ falls short of belief ’ [see Homes v Thorpe [1925] SASR 286 at 291] and ‘ is more than mere idle wondering whether [the situation]... exists or not ’ [see Queensland Bacon Pty v Rees [1966] 115 CLR 266 at 303; [1966] HCA 21]. This principle requires some substance to the suspicion (beyond a hunch) for the establishment of “reasonable cause”.

The police have extensive powers to investigate suspected criminal offences. They can search premises, vehicles and vessels (ships and boats), and seize property when: