§ 8.01 The Constitutional Role of "Probable Cause"

• Jurisdiction: United States

§ 8.01 The Constitutional Role of "Probable Cause"¹

One clause of the Fourth Amendment prohibits "unreasonable searches and seizures." Another clause provides that "no Warrants shall issue, but upon probable cause." The interrelationship of these two clauses is a matter of considerable dispute,²but what is not in dispute is that "probable cause" is a critical feature of Fourth Amendment jurisprudence. One scholar has observed that "the concept of probable cause lies at the heart" of the Amendment.³ As the Supreme Court has suggested, the "rule of probable cause is a practical, nontechnical conception affording the best compromise that has been found" for balancing competing needs: "safeguard[ing] citizens from rash and unreasonable interferences with privacy and from unfounded charges of crime" while, at the same time, "giv[ing] fair leeway for enforcing the law in the community's protection."⁴

The importance of "probable cause" in Fourth Amendment jurisprudence is evident from three general constitutional principles. First, the text of the Fourth Amendment itself provides that arrest and search warrants may only be issued if supported by probable cause. Second, all arrests (even those that do not require a warrant) require probable cause. That is, an arrest — which is one form of "seizure" of a person — on less than probable cause is always constitutionally unreasonable.⁵ Third, in computer terms we might say that "probable cause" is the default position for searches and seizures of property: with rare exceptions, searches and seizures are reasonable if they are conducted with probable cause;⁶ although subject to more exceptions, many searches and seizures conducted without probable cause are constitutionally unreasonable.

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Notes:

^[1] See generally Akhil Reed Amar, Fourth Amendment First Principles, 107 Harv. L. Rev. 757, 782-85 (1994); Fabio Arcila, Jr., In the Trenches: Searches and the Misunderstood Common-Law History of Suspicion and Probable Cause, 10 U. Pa. J. Constit. L. 1 (2007); Tracey Maclin, When the Cure for the Fourth Amendment Is Worse Than the Disease, 68 S. Cal. L. Rev. 1, 25-32 (1994).

^[2] See §§ 4.02-.03, supra, and § 10.01, infra.

^[3] Albert W. Alschuler, Bright Line Fever and the Fourth Amendment, 45 U. Pitt. L. Rev. 227, 243 (1984). Not everyone agrees with this appraisal. Professor Akhil Amar, see Note 1, supra, at 785, points out that the "probable cause" standard is found only in the Warrant Clause of the Fourth Amendment...