Nevertheless, the Court frequently asserts that the most basic constitutional rule in this area is that searches conducted outside the judicial process, without prior approval by judge or magistrate, are per se unreasonable under the Fourth Amendment subject only to a few specially established and well-delineated exceptions. The exceptions are said to be jealously and carefully drawn, and there must be a showing by those who seek exemption . . . that the exigencies of the situation made that course imperative. While the record does indicate an effort to categorize the exceptions, the number and breadth of those exceptions have been growing.
From http://www.gpo.gov/fdsys/pkg/GPO-CONAN-1992/pdf/GPO-CONAN-1992-10-5.pdf
In case you missed it: "per se unreasonable" is the relevant phrase. The exception for hot pursuit was clearly not applicable in Watertown. That is the only possible relevant exception. Some case law has shown a hunch or public view of evidence is acceptable for a search. Thus an officer in Watertown seeing something or feeling suspicious about a particular house could execute a search. But that was not the case in any of the searches in Watertown, all illegal, unless voluntary permission (no pressure) was given.
Did anyone resist?