According to JTN, the U.S. Supreme Court found it in the penumbra of the emanation of "reasonableness". Actually, they found "knock and announce and wait 20-30 seconds" -- how about that?
And who says justices legislate from the bench? That's not legislation, even though it looks like it. Merely an interpretation of what constitutes a reasonable search
Personally, I thought the 4th amendment was referencing a reasonable search -- you know, only what's relevant to the crime and what's outlined in the warrant, certain areas of the house, not the car, not the safe, etc.
The justices seem to believe that the "search" starts as soon as the cops get out of the car.
Wilson v. Arkansas
(O)ur effort to give content to this term may be guided by the meaning ascribed to it by the Framers of the Amendment. An examination of the common law of search and seizure leaves no doubt that the reasonableness of a search of a dwelling may depend in part on whether law enforcement officers announced their presence and authority prior to entering.