FN4.  See LaFave, Search & Seizure 2.2 (“As a general proposition . . . when a law enforcement officer is able to detect something by utilization of one or more of his senses while lawfully present at the vantage point where those senses are used, that detection does not constitute a ‘search’ within the meaning of the Fourth Amendment.”).  In other words, if officers have lawfully entered a room for one purpose and then see contraband unrelated to that purpose lying in plain view (e.g. openly on a desk), they may seize the contraband unrelated to having to obtain a new warrant.