§ 8.02 PROBABLE CAUSE: GENERAL PRINCIPLES

• Jurisdiction: United States

§ 8.02. Probable Cause: General Principles⁷

[A] "Probable Cause": Definition

"Probable cause" is traditionally to defined to exist when the facts and circumstances within an officer's personal knowledge, and of which he has reasonably trustworthy information, are sufficient in themselves to warrant a person of reasonable caution in the belief that: (1) in the case of an arrest, an offense has been committed and the person to be arrested committed it; or (2) in the case of a search, a specifically described item subject to seizure will be found in the place to be searched.⁸

A shorthand way to make the same point is this: A law enforcement officer, as a reasonable person, must have a "good reason" — enough reliable information—to reasonably believe that (in the case of arrest) the person to be arrested committed a crime or (in the case of a search) that the search will uncover evidence relating to a crime.⁹

[B] "Probable Cause": Objective versus Subjective

"Probable cause" is an objective concept. An officer's subjective belief, no matter how sincere, that he has good cause to arrest a person or to conduct a search does not by itself constitute probable cause.¹⁰ It also follows that an officer's lack of belief that he has probable cause does not foreclose a finding to the contrary.¹¹ And, especially controversially, if there is objective probable cause, the officer's subjective motivations for making the arrest or search—even if they are pretextual or malicious — are irrelevant to the "probable cause" finding.¹²

On the other hand, in determining what a so-called "person of reasonable caution" would believe, a court will take into account the expertise of the officer whose actions are under scrutiny. For example, an officer's specialized knowledge of the appearance or odor of a narcotic is relevant in determining whether an officer has probable cause to make an arrest or drug search.¹³ Likewise, an officer's personal experience assigned to patrol a particular area of town, or his many years of detective work, may render his belief that crime is afoot reasonable,¹⁴ even though a reasonable layperson would not have good reason to draw the same conclusion.

[C] "Probable Cause": Arrests versus Searches

The methodology for making a probable cause determination is the same for arrests as it is for searches. However, the result need not be the same in a particular case: that is, an officer might have probable cause to arrest a person but not to conduct a search, or vice-versa. For example, O might have probable cause to believe that he will find contraband in D's automobile, and yet lack probable cause to arrest D, because he may lack sufficient evidence that D is aware of the contraband, a required element of the offense. Conversely, O might have probable cause to arrest D for manufacturing drugs, but if D's arrest occurs at X's house, about which O has no evidence of drug activity, O might lack probable cause to search X's residence for drugs.

Furthermore, evidence that would justify a search is apt to become "stale" sooner than information that is used to justify an arrest. For example, information obtained on January 1 that a small quantity of drugs will be found in D's bedroom might be insufficient to warrant a search on February 1, because the drugs might have been moved or consumed by then. In contrast, if an officer has probable cause to arrest D for possession of drugs on January 1, the arrest will be valid a month later—the "probable cause" is still fresh—unless intervening information casts doubt on the trustworthiness of the earlier information. For example, "probable cause" might no longer exist if the officer subsequently learned that the informant who implicated D had a motive to lie.

[D] "Probable Cause": With or Without Warrants

A central feature of traditional Fourth Amendment jurisprudence is that the constitutionally preferable arbiter of probable cause is a "neutral and detached magistrate," rather than a police officer "engaged in the often competitive enterprise of ferreting out crime."¹⁵

Even when the police are justified in acting without prior judicial authorization—that is, without a warrant—probable cause usually is required. If an officer acts without a warrant, a court subsequently called on to determine whether the officer's actions were reasonable must determine whether the officer had probable cause at the time of the Fourth Amendment activity (i.e., whether a magistrate would have issued a warrant if one had been sought).

In view of "the Fourth Amendment's strong preferences for searches conducted pursuant to a warrant,"¹⁶ the Supreme Court has indicated that "the resolution of doubtful or marginal cases [of probable cause] . . . should be largely determined by the preference to be accorded to warrants."¹⁷ That is, in close probable-cause cases, a search conducted with a warrant should be upheld where a warrantless search might be rejected for want of probable cause.

[E] "Probable Cause": Search for and Seize What?

Originally, a search was unjustifiable unless there was probable cause to believe that it would result in the seizure of one of three categories of evidence: (1) a "fruit" of a crime (e.g., money obtained in a robbery); (2) an instrumentality of a crime (e.g., the gun used to commit a robbery, or the car used in the get-away); or (3) contraband (e.g., illegal narcotics). So-called "mere evidence," that is, items that have only evidentiary value in the apprehension or conviction of a person for an offense, could not be seized.¹⁸

The so-called "mere evidence rule" was founded on property-based concepts consistent with the original understanding of the Fourth...