5. The common law has a number of exceptions to the general rule that a person is a trespasser unless that person enters premises with the consent, express or implied, of the occupier. Thus, a constable or citizen can enter premises for the purpose of making an arrest if a felony has been committed and the felon has been followed to the premises. A constable or citizen can also enter premises to prevent the commission of a felony, and a constable can enter premises to arrest an offender running away from an affray. Moreover, a constable or citizen can enter premises to prevent a murder occurring. In these cases there is power not only to enter premises but, where necessary, to break into the premises. However, it is a condition of any lawful breaking of premises that the person seeking entry has demanded and been refused entry by the occupier. See Swales v. Cox (1981) QB 849, at p 853. Furthermore, a constable, holding a warrant to arrest, may enter premises forcibly, if necessary, for the purpose of executing the warrant provided that the constable has first signified "the cause of his coming, and ... (made) request to open doors": Semayne's Case, at p 91b (p 195 of ER); Burdett v. Abbot [1811] EngR 83; (1811) 14 East 1, at pp 158, 162-163 [1811] EngR 83; (104 ER 501, at pp 561, 563); Lippl v. Haines (1989) 18 NSWLR 620, at p 631. But no public official, police constable or citizen has any right at common law to enter a dwelling-house merely because he or she suspects that something is wrong: Great Central Railway Co. v. Bates (1921) 3 KB 578, at pp 581-582. Nor, except in the instances to which we have referred, can any person enter premises, without a warrant, to apprehend a fugitive who may be on the premises: Lippl v. Haines, at p 636. Another exception to the general rule that a person who enters premises without the express or implied consent of the occupier is a trespasser is the rule that the sheriff can enter premises, by force if necessary, for the purpose of executing process in cases where the Sovereign is a party to the action: see the third resolution in Semayne's Case, at p 91b (p 195 of ER). Moreover, if the door of premises is open the sheriff may enter "and do execut(ion) at the suit of any subject, either of the body, or of the goods" (at p 92a (p 197 of ER)). But the right to execute at the suit of a subject does not extend to breaking open the outer doors of a dwelling-house: Semayne's Case, at pp 92a, 92b (pp 197, 198 of ER); Burdett v. Abbot, at pp 154-155 (p 560 of ER); Southam v. Smout, at pp 322-323, 326, 329; Tomlins' Law-Dictionary, 4th ed. (1835), vol.1, tit. Execution, III. 3. It has been held, however, that, for the purpose of executing process at the suit of any subject, the sheriff may break open a barn or outhouse which is not part of a dwelling-house: Penton v. Brown [1685] EngR 1934; (1664) 1 Keb. 698 (83 ER 1193).