If you conduct a search under this exception and find contraband unrelated to that for which you are searching, you may seize that evidence under the plain view doctrine. The search of an vehicle incident to arrest is another exception to the Fourth Amendment. In the context of an arrest of an occupant of a vehicle, lungable area means the entire passenger compartment, including any open or closed containers therein. The trunk may not be opened incident to arrest absent consent or factors giving rise to the automobile exception. For example, if you arrest the driver on an outstanding warrant, search the passenger compartment and find a small amount of marihuana, you may not open the trunk incident to arrest since you lack probable cause to believe there is more evidence in the trunk.
Consent is an exception to the Fourth Amendment's warrant requirement.
Valid consent to search makes an otherwise unlawful search lawful. You may not, for example, approach folks on the street and demand that they show you what they are carrying in their packages. You may, however, request permission to search anyone's property. You may make such a request whether or not you suspect the person of engaging in criminal conduct. Note that the statement may be oral, written, or even a nod of the head.