In proceedings for an offence under section 7(6), where evidence is given by -

(a) a member of the Garda Síochána,

(b) an immigration officer (within the meaning of the Immigration Act 2004), or

(c) an authorised officer under section 51,

that he or she observed a person doing an act in a particular place, being an act the doing of which, in the circumstances concerned, is consistent with that person's having been employed to do that act in that place, then it shall be presumed, unless the contrary is shown, that that person was employed to do that act in that place.