Chapter 5 describes a uniquely productive type of surveillance known as a binary search. Binary searches reveal no information other than the absence or presence of illegal activity. The Supreme Court has correctly determined that a binary search does not implicate the Fourth Amendment, since an individual does not have a legitimate expectation of privacy in illegal conduct. The cost–benefit analysis theory encourages binary searches, because they are the perfect example of positive sum surveillance: if designed properly, they can increase the level of crime detection without increasing the level of privacy infringement. Soon facial recognition technology and advances in crime recognition software will allow law enforcement to achieve nearly 100 percent enforcement for certain crimes. Such a development, though theoretically desirable, has potentially negative side effects.