Forthcoming, Tulane Law Review, vol. 80 (2005).


This Article discusses the recent Supreme Court decision Illinois v. Caballes, which held that the Fourth Amendment does not bar the use of drug-detection dogs, even in the absence of reasonable suspicion. It argues that the Caballes case paves the way for widespread and indiscriminant use of a new type of surveillance known as a binary search. A binary search is defined as a search which provides the law enforcement official with no information about the subject other than whether or not illegal activity is present. Drug-detection dogs are one example of a binary search, but there are many others which are being developed, such as portable gun detectors or software protocols that sift through all e-mails passing through an internet service provider looking for child pornography.

Since the Caballes case did very little in the way of defining binary searches and discussing the appropriate limitations (if any) on their use, the Article seeks provide some guidance to courts in evaluating the constitutionality of binary searches in the future. The Article begins by discussing the history of the binary search doctrine, focusing on its application to drug-detection dogs, which up until now have been the most common form of binary search in use. The Article then analyzes the Caballes decision itself, examining what it does and does not resolve about the constitutionality of binary searches. Finally, the Article attempt to resolve the important unanswered questions in Caballes: first, how accurate does a surveillance technique have to be in order to be considered a binary search, and second, how does the Fourth Amendment prohibition against unreasonable seizures limit or prevent the widespread use of binary searches?


Criminal Law | Criminal Procedure

Date of this Version

April 2005