What is the test for a search incident to arrest?

It is clear that an officer need not have reasonable and probable grounds to conduct a search incident to arrest but the search must be “truly incidental” to the arrest such that the officer in conducting the search must be attempting to achieve a valid purpose related to the arrest. As Lamer C.J.C. in R v. Caslake 1998 CanLII 838 (SCC), [1998] 1 S.C.R. 51 pointed out at 63, In my view, all of the limits on search incident to arrest are derived from the justification for the common law power itself: searches which derive the legal authority from the fact of arrest must be truly incidental to the arrest in question. The authority for the search does not arise as a result of a reduced expectation of privacy of the arrested individual. Rather, it arises out of a need for the law enforcement authorities to gain control of things or information which outweighs the individual’s interest in privacy. ...This means, simply put, that the search is only justifiable if the purpose of the search is related to the purpose of the arrest. and again at 65 In my view, it would be contrary to the spirit of the Charter’s section 8 guarantee of security against unreasonable searches or seizures to allow searches incident to arrest which do not meet both the subjective and objective criteria. This Court can not characterize a search as being incidental to an arrest when the officer is actually acting for purposes unrelated to the arrest. That is the reason for the subjective element of the test. The objective element insures that the police officer’s belief that he or she has a legitimate reason to search is reasonable in the circumstances.