The police officers were obliged to give the appellant notice, show to her their authority, and demand that they be allowed entry. They may only break open any outer or inner door or window of a house to execute the search warrant if, after such notice and demand, such officers are refused entry to the place of directed search. This is known as the "knock and announce" principle which is embodied in Anglo-American Law. The method of entry of an officer into a dwelling and the presence or absence of such notice are as important considerations in assessing whether subsequent entry to search and/or arrest is constitutionally reasonable.