What is the test for warrantless seizure under the Fourth Amendment?

"[I]f, while lawfully engaged in an activity in a particular place, police officers perceive a suspicious object, they may seize it immediately." (Texas v. Brown (1983) 460 U.S. 730, 739 [75 L.Ed.2d 502, 512].)

"It is, of course, an essential predicate to any valid warrantless seizure of incriminating evidence that the officer did not violate the Fourth Amendment in arriving at the place from which the evidence could be plainly viewed. There are, moreover, two additional conditions that must be satisfied to justify the warrantless seizure. First, not only must the item be in plain view, its incriminating character must also be 'immediately apparent.' [Citations.] . . . Second, not only must the officer be lawfully located in a place from which the object can be plainly seen, but he or she must also have a lawful right of access to the object itself." (Horton v. California (1990) 496 U.S. 128, 136-137 [110 L.Ed.2d 112, 123], fn. omitted.)