A knock-and-talk, like a stop-and-frisk, is a flexible investigatory tool that is used by law enforcement officials to subvert the Fourth Amendment's warrant requirement.
"Fighting For Equal Protection Under The Fourth Amendment: Why "Knock-And-Talks Should Be Reviewed Under The Same Constitutional Standard As "Stop-And-Frisks","
Nova Law Review: Vol. 40
, Article 1.
Available at: http://nsuworks.nova.edu/nlr/vol40/iss2/1