Probable Cause for Vehicles

Probable Cause for Vehicles

The two justifications from the preceding section explain why officers may skip the warrant for a vehicle, and they say nothing about what officers must have in its place. The answer is a single requirement, which this chapter calls the probable-cause trigger: the showing a magistrate would demand before issuing a warrant for the same search. United States v. Ross tied the warrantless search to the warranted one in a formula that California v. Acevedo later repeated: "The scope of a warrantless search based on probable cause is no narrower—and no broader—than the scope of a search authorized by a warrant supported by probable cause."¹ The exception therefore changes who first judges whether the evidence is likely to be in the car, and it leaves unchanged how much has to be shown. Carroll set that pattern, since it approved a warrantless search of an automobile that rested on probable cause to believe the vehicle held evidence of crime.²

The reason for matching the warrant standard follows from what the exception removes. A warrant puts a neutral magistrate between the officer and the search, and a warrantless vehicle search takes that check away, which leaves the officer's own judgment about probable cause as the only safeguard against an arbitrary search. If the standard were lower for cars, the reduced expectation of privacy described earlier would let any officer open any trunk on a hunch, and a search left "at the discretion of the official in the field" is exactly what Camara forbids.³ The Court has accordingly said in Ross that the Carroll exception "applies only to searches of vehicles that are supported by probable cause," and in Almeida-Sanchez v. United States it put the point more bluntly: "Automobile or no automobile, there must be probable cause for the search."⁴

Probable cause is the only thing officers must add, because the exigency belongs to the vehicle by its nature. Carroll's account of the problem spoke of a category of movable vessels and vehicles that can be quickly taken out of the place where a warrant must be sought, so the exigency attaches to the kind of thing searched, and the officer's showing about the particular car is probable cause.⁵ This trigger also differs from the one for a search incident to arrest. There the threshold question is whether the driver or a passenger has been arrested, and no separate showing of probable cause to believe evidence is in the car is required.⁶ The automobile exception asks a different question, which is whether the officers have probable cause to believe that this vehicle contains contraband or evidence of crime.⁷

The two poles of the trigger appear in the cases. In Ross an informant told police that he had watched Ross complete a drug transaction using drugs stored in the trunk of his car. The police stopped the car, opened the trunk, and found a brown paper bag containing drugs, and the Court held the warrantless search reasonable under the Fourth Amendment.⁸ The report tied one car and one compartment to the contraband, which gave the officers the concrete link a magistrate would have looked for. Almeida-Sanchez shows the failure of the trigger. That case arose from the use of roving patrols to stop and search vehicles for illegal aliens, and the Court held that a warrantless search of a vehicle without probable cause violated the Fourth Amendment.⁹ The fact that the target was a car did not help the government, because the exception supplies a reason to skip the warrant and leaves the probable-cause requirement in place.

On an exam stem that begins with a routine traffic stop, the temptation is to treat a valid stop for faulty equipment as if it licensed a search of the car. The stop and the search rest on different showings, and the exception reaches only the search that probable cause supports.

What counts as probable cause for a particular car is the next question. The first subsection below states the standard and shows how the agents in Carroll satisfied it, and the second applies the standard to a modern source of probable cause, the alert of a trained narcotics-detection dog during a traffic stop.

The Fair-Probability Standard

The probable-cause trigger needs a working definition, and the Court has supplied one that fits in a single sentence: probable cause to search exists when there is a fair probability that seizable evidence or contraband will be found in a particular place.¹¹ Seizable evidence means whatever the officers are entitled to take, such as contraband, the fruits of a crime, or the tools and records of one. The sentence has two working parts, and each has its own reason. The words fair probability set how sure the officers must be, and the words particular place require that something connect the officers' information to the vehicle they propose to open. The same level of cause is needed to obtain a warrant, which is why the exception changes who judges the question and leaves unchanged how much must be shown.¹²

Fair probability sets the certainty level well below proof. In Florida v. Harris, taken up in the next subsection, a unanimous Court restated the standard: the test cannot be reduced to a precise definition or a percentage, the trial yardsticks of proof beyond a reasonable doubt and preponderance of the evidence have no place in the decision, and the required showing is the kind of probability on which reasonable and prudent people, rather than legal technicians, act.¹³ The Court added that courts weigh the totality of the circumstances and reject rigid rules, bright-line tests, and mechanical checklists.¹⁴

The reason for so practical a threshold follows from what a search is for. Officers open a car to learn whether evidence is inside, so a rule demanding proof that the evidence is inside would forbid the very search that could supply the proof. A long-standing description of the rule makes the same point: it is a practical, nontechnical conception that leaves room for the mistakes of reasonable people acting on facts that lead sensibly to their conclusions of probability.¹⁵ The judgment is made from the standpoint of an objectively reasonable officer, so a private hunch adds nothing to the calculation, although the officer's experience is entitled to due weight in reading what the observed facts suggest.¹⁶

The second part, a particular place, keeps the exception from becoming a license to search any car on the road. Information that a crime occurred somewhere, or that a person is suspected of wrongdoing, says nothing by itself about the inside of a given vehicle. The officers need facts that tie the object of their search to this vehicle, and the two illustrations below show what kinds of facts do that work. The tie matters again later in this chapter, because the object the officers have reason to look for will define how far the search may go.

In Carroll the link came from the agents' own dealings with the defendants. On September 29, 1921, federal prohibition agents posing as buyers met Carroll and Kiro in a Grand Rapids apartment and negotiated the purchase of three cases of whiskey, which the defendants agreed to deliver and never did.¹⁷ On October 6 the agents saw the defendants' car on the road heading toward Detroit and lost it near East Lansing, and on December 15 they recognized the same car and the same occupants traveling from the direction of Detroit toward Grand Rapids.¹⁸ The negotiation showed that these men dealt in whiskey, and the repeated sightings tied that particular car to them and to the road they had been seen using. Those facts supplied the fair probability the standard requires, and the Court upheld the warrantless search that turned up sixty-nine quarts of whiskey behind the rear seat.¹⁹

Viewed one fact at a time, the agents' evidence looks thin, and Justices McReynolds and Sutherland dissented.²⁰ A critic can say that a failed whiskey deal in September and a lost trail in October reveal nothing about what the car held on December 15. The answer built into the standard is that probable cause is a judgment about the whole picture, and that it asks for a probability reasonable people would act on, not certainty. Each fact was weak alone, but together they pointed at one car, one pair of men, and one kind of contraband.

Chambers v. Maroney supplies a second illustration, in which the link came from eyewitnesses rather than from the officers' own dealings. On May 20, 1963, two men armed with guns robbed a Gulf station in North Braddock, Pennsylvania.²¹ Two teenagers had noticed a blue compact station wagon circling the block and then saw it speed away, and they reported that four men were inside and one wore a green sweater; the attendant added that one robber wore a green sweater and the other a trench coat.²² Within an hour police stopped a light blue compact station wagon carrying four men, one of them in a green sweater, with a trench coat in the car. The Court held that the police had probable cause to arrest the occupants and, just as obviously, to search the car for guns and stolen money.²³ The description matched this car and these men to the robbery, and the offense itself told the officers what to look for, since armed robbers who flee by car carry their guns and the money with them.

The same passage of Chambers draws the contrast. In Preston v. United States the arrest was for vagrancy, and it was apparent that the officers had no cause to believe evidence of any crime was concealed in the car.²⁴ In Dyke v. Taylor Implement Mfg. Co. the Court expressly rejected the suggestion that there was probable cause to search the car.²⁵ An arrest was present in both Chambers and Preston, so the arrest cannot explain the different results. The robbery generated facts that pointed to guns and money in a described car, while a vagrancy arrest generated none, because that offense leaves no fruits or instruments to hide in a vehicle. An arrest gives officers a reason to hold the person, and what it says about the car depends on the crime and the facts attached to it. The trap on an exam stem is to treat the arrest or the stop itself as the probable cause for the search.

Step three does the real work on exam facts, since stems routinely pile up lawful-stop and lawful-arrest details that never reach the car. The next subsection applies the same four steps to a modern source of facts, the alert of a trained narcotics-detection dog.

Drug-Dog Alerts

The four steps from the last subsection ask which facts, known before the search, make it fairly probable that the object of the search is in this vehicle. A trained narcotics-detection dog supplies one of the most common modern answers to that question. In Florida v. Harris a unanimous Court held that the alert of a trained and certified detection dog during a traffic stop can provide probable cause to search the vehicle, absent special circumstances undermining the dog's reliability. It also held that formal field-performance statistics are not necessarily required when training and certification evidence shows the dog is reliable.²⁷ This section treats that decision as a referred authority, applying the fair-probability standard to one source of facts without retelling the whole case.

The setting in Harris was ordinary. Officer Wheetley pulled Harris over for a routine traffic stop, noticed Harris's nervousness and an open beer can, and asked for consent to search the truck. When Harris refused, Wheetley ran a sniff test with his trained dog, Aldo, and Aldo alerted at the driver's-side door handle. The search found nothing Aldo was trained to detect, but it did turn up pseudoephedrine and other ingredients for making methamphetamine.²⁸ The Florida Supreme Court had required a wide array of evidence in every case, including field records of how often the dog had falsely alerted, so that an officer who kept no such records could never have probable cause.²⁹ The Supreme Court reversed, because the training and testing records supported Aldo's reliability and Harris had not undermined that evidence.³⁰

The Court rejected the Florida checklist because probable cause is judged on the totality of the circumstances, and a list of independent requirements, every one of which must be met, cannot coexist with that approach.³¹ The Court drew the comparison to informants. In Illinois v. Gates it had abandoned a rigid test for informants' tips, because a gap on one requirement could defeat probable cause even when other signs of reliability were strong, and the same flexibility governs a dog, so that a weakness in one kind of proof can be made up by a strong showing of another.³² The comparison fits because a dog's alert works like a tip, in that the officer relies on a source to say where contraband is, and the real question is how far the source can be trusted. Training and certification records answer that question better than field statistics do. Field records count only what officers happen to find, so they can overstate a dog's false alerts and cannot capture the contraband the dog missed, while records from standard training and certification settings carry no such distortion.³³ Field records may still matter when they exist, but a court weighs all the evidence and does not demand a fixed set of documents.³⁴

Because the inference rests on reliability, it can be defeated. The alert supports probable cause when nothing undermines the dog, and a defendant remains free to contest the dog's reliability.³⁵

Whatever probable cause an alert supplies reaches only the object the dog was trained to detect. A narcotics dog's alert is a report about narcotics, so it ties drugs to the vehicle and says nothing about stolen goods or weapons, which means the first step of the checklist, identifying the object of the search, still controls. The result of the search does not rewrite the analysis either. The search of Harris's truck found nothing Aldo was trained to detect, yet the Court found probable cause, because the question is what the facts available to the officer would lead a person of reasonable caution to believe when the officer acted.³⁶ On an exam stem, the trap is to demand field-performance statistics before treating an alert as probable cause. A trained and certified dog with no contrary evidence of unreliability is enough.

The next section leaves the question of what justifies a vehicle search and asks when the search may take place.