Craig Bradley (Indiana University School of Law-Bloomington) has posted 'Knock and Talk' and the Fourth Amendment (Indiana Law Journal, Vol. 84, No. 4, 2009) on SSRN. Here is the abstract:
"Knock and talk" is a technique employed by police, in theory, to make legitimate inquiries about alleged criminal activities by knocking on people's doors and talking to them about the allegations. In fact, it is used to check out yards and to get views (and smells) from the inside of houses, as well as to locate potential arrestees, without probable cause or a warrant. If the information thus obtained amounts to probable cause, either to search or arrest, the police then claim "exigent circumstances," enter the house, search, arrest, and search further incident to arrest, all without a warrant. Although the Supreme Court clearly disapproved of this sort of activity in 1948 in Johnson v, United States, 333 U.S. 10, that case has been largely ignored by the courts of appeal, which have widely approved of "knock and talk." The Supreme Court has not addressed this subject since Johnson. This article reviews the many cases on this issue and suggests some possible limits on the police.
