VALID WARRANTLESS SEARCHES:

The following are the well-recognized instances where searches and seizures are allowed even without a valid warrant: (1) Warrantless search incidental to a lawful arrest: (2) [Seizure] of evidence in "plain view." The elements are: a) a prior valid intrusion based on the valid warrantless arrest in which the police are legally present in the pursuit of their official duties; b) the evidence was inadvertently discovered by the police who have the right to be where they are; c) the evidence must be immediately apparent; and d) "plain view" justified mere seizure of evidence without further search; (3) Search of a moving vehicle. Highly regulated by the government, the vehicle’s inherent mobility reduces expectation of privacy especially when its transit in public thoroughfares furnishes a highly reasonable suspicion amounting to probable cause that the occupant committed a criminal activity; (4) Consented warrantless search; (5) Customs search; (6) Stop and Frisk; (7) Exigent and emergency circumstances; (8) Search of vessels and aircraft; [and] (9) Inspection of buildings and other premises for the enforcement of fire, sanitary and building regulations.  x x x  

In the exceptional instances where a warrant is not necessary to effect a valid search or seizure, what constitutes a reasonable or unreasonable search or seizure is purely a judicial question, determinable from the uniqueness of the circumstances involved, including the purpose of the search or seizure, the presence or absence of probable cause, the manner in which the search and seizure was made, the place or thing searched, and the character of the articles procured (VALEROSO vs. COURT OF APPEALS, G.R. No. 164815, September 3, 2009, 3rd Div, Nachura, J.).