Ending the Zero-Sum Game: How to Increase the Productivity of the Fourth Amendment
Simmons, Ric, Harvard Journal of Law & Public Policy
B. Surveillance Techniques Which Are as Effective but Less Intrusive
Another way to increase productivity is to develop surveillance techniques that provide the same level of output but cost less in terms of privacy costs. In general, law enforcement agencies will be indifferent as to whether to use these methods, or equally expensive but more intrusive methods because once again they are indifferent to the "savings" in terms of the cost to privacy.
1. Binary Surveillance
Binary surveillance refers to a surveillance method that only produces one of two results: positive (meaning that illegal activity has been detected) or negative (meaning that illegal activity has not been detected). (92) The surveillance provides no other information about the person or area being monitored, and so represents a relatively minor intrusion on the target's privacy. In fact, the Supreme Court has held that binary surveillance does not even count as a "search" under the Fourth Amendment because it does not infringe on an expectation of privacy that society is prepared to recognize as legitimate. (93)
A simple example of a binary surveillance technique is a field test for narcotics. If a law enforcement officer reasonably believes that a certain substance may be narcotics, she can legally seize a very small amount of the substance and mix it with certain chemicals. (94) If the substance tests positive for narcotics, the law enforcement officer knows that the substance is in fact contraband and that a crime has occurred. If the substance tests negative, the officer knows nothing about the substance other than the fact that it is not an illegal drug. Therefore, because the suspect has no legitimate interest in possessing contraband, assuming other procedural prerequisites are satisfied, the surveillance does not implicate the Fourth Amendment (95)--the officer either learns nothing at all about the defendant or learns that the defendant is engaging in illegal activity.
Under our analysis, binary surveillance would theoretically provide us with a very high level of surveillance productivity because the cost in terms of intrusiveness is almost nothing. In practice, however, there are a number of complications when applying our model to binary surveillance. First, simply because the surveillance does not implicate the Fourth Amendment does not mean it has no cost in terms of privacy intrusion. For example, a drug-sniffing dog that approaches an individual's belongings, home, or person represents some level of intrusion, (96) even if there is no chance that the surveillance will reveal any legitimate information about your possessions. Thus, the binary surveillance itself creates some privacy cost. Furthermore, many types of binary surveillance will lead to a more intrusive search. A drug-sniffing dog alerting to a suspect's car or suitcase will trigger a thorough physical search. If the drug dog has a very low false positive rate, then it would result only in a more intrusive search on those rare occasions when contraband actually was present. Thus, this extra privacy cost would be relatively low. But in practice this is not the case: According to some estimates, when drug dogs alert, they are correct only between 26% and 44% of the time. (97) Therefore, in calculating the total privacy costs of binary surveillance, the privacy cost of a physical search times the percentage chance that the dog has improperly alerted must be added to the equation.
Finally, there is one more element to our total privacy cost calculation: a correct positive alert will also result in a physical search. Thus, we must include the privacy cost of a physical search multiplied by the percentage chance that contraband actually is present. Although the Supreme Court has stated that individuals who possess narcotics have no legitimate expectation of privacy in the contraband they carry, (98) a physical search that finds this contraband will involve a significant level of intrusion and will reveal other information about the suspect that is protected. …