§ 8.07 HOW PROBABLE IS "PROBABLE CAUSE"?

• Jurisdiction: North Carolina

§ 8.07. How Probable Is "Probable Cause"?⁸⁴

[A] Governing Law

Suppose that O, a police officer, observes A and B standing over V's body. Assume further that O has reason to believe, nearing 100% certainty, that A or B, but not both, murdered V. The odds, however, are equal as to which one is guilty. Or, suppose that, after a car accident, O determines that both occupants of the car were intoxicated, but each accuses the other of being the driver.⁸⁵ May O constitutionally arrest both suspects in these cases, knowing that one is innocent?⁸⁶ Is the answer different if three, rather than two, suspects are at the scene, and only one is guilty? Or, what if O is virtually certain that a murder suspect is hiding in one of two (or three) houses. May the police simultaneously search both (or all three) houses to find the suspect? The essential question raised by these scenarios is this: How certain must the "person of reasonable caution" be before arresting a suspect or conducting a search and seizure, or before a magistrate authorizes such activity?

The Supreme Court has never quantified "probable cause." To the contrary, it has described probable cause as a "fluid concept,"⁸⁷ "incapable of precise definition or quantification into percentages because it deals with probabilities and depends on the totality of the circumstances."⁸⁸ Instead, the Court uses phrases such as "fair probability," "substantial basis," and "reasonable grounds" to articulate the quantum of evidence necessary to prove "probable cause."

While the Court eschews a precise quantification of the concept, this much is known: Less evidence is required to justify an arrest or search based on probable cause than to convict a person at trial, but more is required than "bare" or "mere" or even "reasonable suspicion."⁸⁹ More specifically, the "probable cause" standard "does not demand any showing that such a belief be correct or more likely true than false."⁹⁰ In other words, whatever else it may mean, "probable cause" involves less than a "50%+" likelihood of accuracy.

Consequently, in the hypotheticals described above, O has probable cause to arrest (or search) two suspects, even if O knows that one of the suspects is innocent;⁹¹ or, it would seem counter-intuitively, O could flip a coin and arrest (or search) one of two suspects even based on the knowledge that there is a 50 percent chance that he picked the wrong person. On the other hand, Supreme Court dictum, albeit in a very old case, implies that the arrest of three persons, only one of whom could be guilty, is unconstitutional for want of probable cause.⁹²

[B] Reflections on the Issue

Precedent and dictum aside, is the Court justified in permitting arrests and searches on less than a preponderance of the evidence? One plausible answer is, "It depends." That is, "probable cause" might be determined on a sliding scale, in which the degree of suspicion required would depend on a balancing of the individual and societal interests implicated in the particular case. This possibility is discussed in subsection [C]. However, even if the degree of "probable cause" were to vary depending on the circumstances, one question would persist: How probable should "probable cause" be in the ordinary, run-of-the-mill, arrest or search case, before one looks at the exceptional cases that justify a heightened or reduced level of probability?

In an ideal world, problems such as those hypothesized in subsection [A] would not occur. For example, O might be able to avoid the dilemma of arresting A and B by briefly detaining both suspects at the scene rather than arresting them, and questioning them long enough to determine which person is (even slightly) more likely guilty. But, even if he did so, A and B might refuse to answer O's questions, or their answers might not assist in focusing suspicion on one of them, in which case O would be back where we started.

The question that ultimately must be answered is this: In what type of society do we wish to live? Do we think it is better that both persons, one of whom is nearly certainly guilty of an offense, remain free while the police seek more evidence, than that O arrest them both, knowing that one of them is innocent, and seek post-arrest evidence that incriminates one and/or exculpates the other?

The conclusion that O may arrest A and B for a crime that O knows only one committed is troubling, but arguably is correct. To permit O to arrest both suspects provides society needed leeway without "leav[ing] law-abiding citizens at the mercy of the officers' whim or caprice."⁹³ After all, it may be said that "the function of arrest [is not] merely to produce persons in court for purposes of the prosecution. . . . [T]here is also an investigative function" — time to determine which suspect is guilty — "which is served by the making of arrests."⁹⁴

An officer who acts on a 50% likelihood that the person arrested is guilty has arguably conducted a reasonable seizure of the person, at least if the alternative is to arrest neither suspect and, thus, knowingly allow a criminal to be free. As the Court has observed in a different context, "what is generally demanded of the many factual determinations that must regularly be made by agents of the government . . . is not that they always be correct, but that they always be reasonable."⁹⁵

Even if an arrest or search based on a 50% chance of accuracy satisfies us, this only shifts the debate to the more difficult question: How much lower likelihood of accuracy are we prepared to accept? At what point does the interest in protecting the community from crime give way to the Fourth Amendment interest in safeguarding citizens from rash and unreasonable interferences with their personal security or privacy?

One scholar, Joe Grano, has gone so far as to contend that an officer who suspects 10 persons of a crime, but who has no way of distinguishing among them, should be permitted in some circumstances to arrest all 10, and then seek evidence later to clear the nine innocent parties.⁹⁶ According to him...