While that outcome may please many who favor strong Fourth Amendment protection, its ultimate effect has been just the reverse. For the consequence of the Court's rigid adherence to the probable cause standard for searches has been judicial reluctance to apply the latter term even to government actions that clearly involve looking for evidence of crime. Instead, a wide array of intrusive police actions- flyovers of backyards, open field trespasses, undercover activity-have been immunized from Fourth Amendment strictures.
Like the stop and frisk at issue in Terry, these types of investigative techniques are usually exploratory, and thus usually based on a smidgeon of suspicion, rather than probable cause. And without these techniques, probable cause might never be developed. When forced to choose between ending such investigative actions or permitting them whenever police want to use them, even many aggressive civil liberations might choose the latter route. It is no surprise that the Supreme Court, which has to worry about both sides of the balance, has done so.
Thus, in holding that the Fourth Amendment does not govern use of undercover agents to gain entry to the home, Chief Justice Warren himself stated "[w]ere we to hold the deceptions of the agent in this case constitutionally prohibited, we would come near to a rule that the use of undercover agents in any manner is virtually unconstitutional per se. " n19 … Given these developments, some have argued that the real problem in these cases is not the probable cause requirement but Katz's adoption of privacy as the linchpin of Fourth Amendment analysis.
Various other concepts-among them, government-citizen trust, coercion and property-have been proposed as substitutes. n26 I have argued elsewhere that none of these concepts satisfactorily capture the gravamen of the Fourth Amendment. n27 But even assuming one or more of these alternatives is conceptually viable, there is no reason to believe that any of them would have fared better in dealing with the conundrum created by the probable-cause- forever position. Consider property, probably the most commonly touted substitute for privacy as the core Fourth Amendment value.
Of course, privacy analysis takes property interests into account; one has more of a privacy interest in a house one owns or rents than in a house that one temporarily occupies as a guest. Commentators such as Morgan Cloud, however, want a Fourth Amendment "rooted in property theories. " n28 Cloud prefers this approach in large part because, he says, property concepts are less "malleable" than privacy concepts and thus less likely to permit [*609] significant encroachments on the Fourth Amendment's scope.
n29 But property doctrine is eminently manipulable as well: back in the heyday of the property-oriented approach to the Fourth Amendment, the Court had no problem permitting suspicionless searches of privately-owned open fields. n30 The definition of criminal "instrumentalities" was also stretched beyond recognition so that government could assert a superior possessory interest over personal property, n31 a ploy that would be vastly facilitated today by the advent of forfeiture statutes giving government an interest in any item with a "nexus" to criminal activity.
n32 Worse yet, surveillance of any kind could easily be said to be ungoverned by the Fourth Amendment in a property-oriented regime, since it does not involve physical trespass. n33 In other words, even had the Court adhered to a property-based Fourth Amendment, it could have (and undoubtedly would have) succumbed to the anti-regulatory pressure created by the probable-cause-forever position. … As Justice Scalia stated in Griffin v. Wisconsin, "[t]he Constitution prescribes . . .
that where the matter is of such a nature as to require a judicial warrant, it is also of such a nature as to require probable cause. " n34 The converse of this statement, at least as far as the Court is concerned, is that if probable cause is not required, neither is a warrant. Thus, the suggestion by Justice Blackmun in his dissent in Griffin that the search of a probationer's home should be considered reasonable only if authorized by a judge was brusquely dismissed by the majority once it found that such searches present a special needs situation outside normal law enforcement.
n35 According to the majority, a court order based on less than probable cause is "a combination that neither the text of the Constitution nor any of our prior decisions permits. " n36 The idea that a court could issue an order on mere reasonable suspicion or something less in connection [*610] with normal law enforcement would likely be even more oxymoronic to the justices who joined this language. In a variety of ways, then, the probable-cause-forever dogma forces courts grappling with the realities of law enforcement to exempt many varieties of surveillance from the Fourth Amendment's restrictions.
That dogma is not required by the Fourth Amendment, however. The Fourth Amendment only requires that searches and seizures be reasonable. That declaration, of course, conjures up the specter of a Fourth Amendment swallowed up entirely by the special needs exception. But there are other ways of conceptualizing reasonableness. I have argued that the Fourth Amendment would be much better served through the adoption of two principles-the aforementioned proportionality principle, and the exigency principle.
n37 The proportionality principle allows courts to modulate the cause needed to carry out a search depending upon its intrusiveness. Under the proportionality approach, searches of houses would require more cause than searches of open fields, but both would require justification, just as arrests require more cause than stops, but both are governed by the Fourth Amendment. The exigency principle requires ex ante review of any non-exigent search-even one that does not require probable cause under proportionality analysis.
Yet that principle does not have to be inconsistent with the Fourth Amendment's Warrant Clause if, as some Court decisions seem to contemplate, one is willing to adopt a sliding scale definition of probable cause so that warrants can issue on varying degrees of cause, n38 or if the ex ante review is conducted by someone other than a judge or is called something besides a warrant-moves which even Scalia has conceded are possible in special needs situations. n39
The proportionality and exigency principles ameliorate the pressure created by the probable-cause-forever stance without sacrificing the core protection of the [*611] Fourth Amendment. Under this regime, courts would be more willing to say that police attempts to find evidence are "searches" because the consequence of such a holding would not be as dramatic. For instance, undercover work, even if called a search, might only require probable cause when it involves long-term infiltration.
n40 … And all subpoenas for records could more comfortably be called searches because only subpoenas for personal records like those sought in Miller or Smith would require heightened cause; subpoenas for impersonal, organizational records could be obtained on the traditional relevance grounds. n42 Under the proposed regime, then, courts could more easily avoid the temptation to define the Fourth Amendment threshold in terms of assumptions of risk, and might be more willing to speak of that threshold in the terms Katz originally stood for: expectations of privacy society recognizes as reasonable. n43 …