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Student Projects

For Further Study:

  • Michael W. Markowitz & Delores D. Jones-Brown, The System in Black and White: Exploring the Connections Between Race, Crime, and Justice (Michael W. Markowitz & Delores D. Jones-Brown eds., 2000).

  • Thomas N. McInnis, The Evolution of the Fourth Amendment (2009).

  • Frederick Schauer, Profiles, Probabilities, and Stereotypes 811-816 (2006).

U.S. v. Mendenhall, U.S. v. Sokolow, and the Drug Courier Profile Evidence Controversy

Compiled by Larissa Cespedes-Yaffar, Shayona Dhanak, and Amy Stephenson


Imagine the following scenario: you are traveling alone and are stopped by police because you match an officer’s drug courier profile.  The enforcement agents request permission to search your bags or the interior or trunk of your car or truck.  Knowing you have nothing to hide, you graciously give consent.  To your surprise, the police find something and you are quickly arrested for carrying illegal drugs.  Incredible?  Not really!  What is incredible is what may happen next.

After being arrested, you begin to have hope: surely when you appear before the court, the situation will be resolved quickly and painlessly.  You did not put drugs in your luggage, you had no idea you were carrying them, and you certainly had no intent to distribute them. However, the fact that you matched a "drug courier profile" may be used as a justification for a stop or used as evidence of guilt. Courts seem to be split on using the drug courier profile as evidence of guilt. Nevertheless, some courts have concluded that it is contrary to law but its admission is only harmless error.

In an effort to win the "War on Drugs," law enforcement agencies are using drug courier profiles to identify and detain persons who display characteristics that law enforcement agents believe are typical of drug traffickers.  Using the reasonable suspicion standard, courts have upheld the use of these profiles against Fourth Amendment challenges.

The Fourth Amendment

The Fourth Amendment protects citizens "against unreasonable searches and seizures." 1 Traditionally, seizures governed under the Fourth Amendment have been considered arrests, which must be based upon facts amounting to probable cause to survive constitutional scrutiny.2  But because the Fourth Amendment only applies to "unreasonable searches and seizures," the Supreme Court has circumvented the need for a warrant based on probable cause by concluding that a search or seizure was reasonable.3 In Camara v. Municipal Court of the City and County of San Francisco, the Supreme Court held that there is "no ready test for determining reasonableness other than by balancing the need to search against the invasion which the search entails."4 Therefore, when a court finds that the governmental interest outweighs the relative intrusiveness of the search or seizure, the search or seizure is reasonable and the mandates of the Fourth Amendment are satisfied.5

A year after Camara was decided, the Supreme Court extended the Camara balancing test into the criminal arena in the landmark case of Terry v. Ohio.6 In Terry, the Supreme Court recognized a less intrusive category of seizures—the brief investigation detention, or the "Terry stop."  Here, the Supreme Court recognized for the first time an exception to the requirement that the Fourth Amendment seizure of persons must be based on probable cause. Applying the Camara balancing test to the context of "stop and frisk," the Supreme Court decided that brief investigative seizures, or stops, constituted an intermediate category of police-citizen transactions falling between traditional arrests and consensual encounters.  Unlike consensual encounters, which do not implicate Fourth Amendment concerns, the Court held that the Fourth Amendment did regulate these stops and, therefore, the stops must be based on a general standard of reasonableness.7

In determining the reasonableness of the "stop and frisk" at issue in Terry, the Court first examined the government’s interests furthered by this practice.  First, the Court noted the government’s interest in effective crime prevention and detection, which is enhanced by allowing an officer to approach a person for investigatory purposes in situations where the officer lacks probable cause to arrest that person. The Court then addressed the level of intrusion the "stop and frisk" creates for individual citizens and found the practice to be very intrusive, describing it as an "annoying, frightening, and perhaps humiliating experience."8 Taking into account both the government's and the individual citizen interests, the Court ultimately decided that by restricting an officer’s ability to stop a person without probable cause and limiting the extent of the subsequent search, the "stop and frisk" procedure would be reasonable under the Fourth Amendment.

Origins of the Drug Courier Profile

The drug courier profile was developed in the early 1970s by a single agent of the Drug Enforcement Agency ("DEA") for use in investigating commercial air passengers suspected of carrying illegal narcotics.9  Special Agent Paul Markonni is credited with developing the profile while assigned to the DEA’s Detroit office.10

Although Agent Markonni was the first to use a profile to address the nation’s drug problem, the concept of profiles was first used by law enforcement in the United States in 1968 by the Federal Aviation Administration ("FAA") in an attempt to curb the growing skyjacking problem.11 In 1968, the FAA appointed a special task force to investigate methods for combatting hijackings.  This task force enlisted the services of experts who, after conducting field tests and studies, designed a multifactor system to prevent further hijackings.12  Part of the system included the development of a "skyjacker profile."  In the FAA system, passengers boarding an aircraft were observed and compared with this profile. If a passenger fit the profile, airline employees and FAA agents would target that particular passenger.  Implementation of the skyjacker program proved very effective at reducing the number of hijackings in the United States.13

By 1979, the drug courier profile was in use in over twenty airports.14 By 1985, the drug courier profile had extended to airports from Florida to Washington and New England to southern California.15 Currently, police agents throughout the country utilize the drug courier profile in a relatively uniform manner.

How the Drug Courier Profile Works

DEA agents and police officers stationed at airports observe arriving and departing travelers on certain flights. Law enforcement agents watch for "characteristics and behavioral traits which, on the basis of their collective experience, have tended to distinguish drug couriers from other passengers."16 When a specific traveler arouses the agents’ suspicions, they approach the suspect, identify themselves, ask the suspect to consent to questioning, and ask to see the suspect’s identification and ticket.17  If the agent’s suspicions are not eliminated during the first part of the questioning, they continue to question the suspect and ask him to move to another location within the airport, often a room used by law enforcement officers. At this point, the suspect is typically asked to consent to a search of his person, luggage, or both.18 If the suspect voluntarily consents to the police requests at any stage of the transaction, the police are free to continue the investigation.19 If the suspect does not consent and attempts to depart, the police must either allow him to proceed on his way or hold him.20

The drug courier profile comes into play in two ways in the typical police-citizen transaction. Initially, it may trigger investigative action by arousing the agents’ suspicions about a particular traveler. Agents allegedly rely on the profile to identify potential drug couriers.  Additionally, the drug courier profile is a factor the police consider in deciding whether to seize a suspect.

Unlike the FAA skyjacker profile, there is no uniform drug courier profile throughout the nation. Instead, agents create their own individual profiles based on their own professional experiences and observations. Some common characteristics do exist.  One factor common to virtually all drug courier profiles is that a "source city" is involved.21 Source cities include those cities "from which drugs are shipped to other points for sale or further distribution" and those cities that receive the drugs.22 Other characteristics common to most drug courier profiles are the methods by which the suspect makes reservations and purchases tickets, nervousness, the amount of luggage, and the presence of companions.23

Because there is no uniform profile, the profiles are molded by the experience of the officer designing and implementing them.

Supreme Court Decisions: Mendenhall and Sokolow

In U.S. v. Mendenhall, two DEA agents at Detroit Metropolitan Airport observed the defendant disembark from a flight from Los Angeles, a known "source city" for narcotics.  One agent testified at trial that because the defendant’s characteristics fit the drug courier profile, the agents approached the defendant and discovered that she was traveling under an alias.  After obtaining her consent for a search, the agents found two small packages of heroin.

In Mendenhall, the Supreme Court did not address the issue of whether the agents were justified in initially stopping the defendant.  Instead, the Court focused on whether the defendant had consented to the agent’s questioning.  Because she had consented to the search, the Court found that the entire encounter did not reach the level of "seizure" and the Fourth Amendment requirements did not apply.  The Mendenhall decision is significant because it defines seizure under the Fourth Amendment. The Court concluded that a person has been "seized" within the meaning of the Fourth Amendment only if, in view of all of the circumstances surrounding the incident, a reasonable person would have believed that he was not free to leave. Examples of circumstances that might indicate a seizure, even where the person did not attempt to leave, would be the threatening presence of several officers, the display of a weapon by an officer, some physical touching of the person of the citizen, or the use of language or tone of voice indicationg that compliance with the officer's request might be compelled. The Court, however, did not decide whether the actions of the DEA agents would have been justified had there been a seizure.

A more recent Supreme Court decision dealing with drug courier profiles is U.S. v. Sokolow.24  In Sokolow, DEA agents who had been monitoring his trip to Miami arrested the defendant during a layover in Los Angeles on his return trip to Hawaii.  In Los Angeles, DEA agents observed that the defendant was constantly scanning the area, wearing the same black jumpsuit as three days before, and appeared very nervous.  After stopping him, the DEA agents escorted the defendant back to their airport offices.  There, the agents submitted the defendant’s luggage to a canine sniff and arrested the defendant based on the dog’s reaction to the bag.  The agents later discovered 1,063 grams of cocaine in the defendant’s luggage.

The Supreme Court reversed the Ninth Circuit’s holding that the agents did not have reasonable suspicion to justify a stop of the defendant.  Instead, the Supreme Court applied a "totality of the circumstances" test, asking whether all the circumstances known to the agents at the time of the stop gave rise to reasonable suspicion.  In this case, the Court believed the DEA agents had developed reasonable suspicion by the time the defendant was "stopped."  In addressing whether reasonable suspicion existed, the Court stated that the fact these same circumstances happened to be contained in a drug courier profile did not change the result.  The defendant’s behavior gave rise to reasonable suspicion regardless of whether it conformed to a drug courier profile.

The Court’s decision in Sokolow does not resolve the confusion resulting from its previous decisions.  In applying the Terry reasonable suspicion standard to the Sokolow case, the Court did not address whether the profile used by the agents was adequate to give rise to reasonable suspicion.  Instead, the Court rested its decision on the specific "totality of the circumstances."  The question remaining after Sokolow is whether a drug courier profile, used under any circumstances, is constitutionally permissible.

How is the Drug Courier Profile Problematic?

In cases of drug courier profiles, the characteristics that often lead an agent to stop an individual also belong to many innocent people.  The agent’s "hunch" is based on his or her experience, and that "hunch" dictates who fits the profile.  The lack of objective standards makes it impossible to apply the reasonable suspicion test to a drug courier profile.  An officer cannot point to any articulable, objective facts that would suggest to the court that criminal activity was afoot besides what his or her own experiences and instincts told him or her.

Without the benefit of the officer’s experience, a reviewing court has nothing on which to base its evaluation of the stop.  The court therefore must rely on the judgment of the officer in implementing the profile.  Consequently, the agent who implements a profile also effectively becomes the one who reviews it. The danger in this situation is that potential abuses may go unchecked. As stated by the Court of Appeals for the Eleventh Circuit in U.S. v. Hernandez-Cuartas:

"Drug courier profiles are inherently prejudicial because of the potential they have for including innocent citizens as profiled drug couriers. Generally, the admission of this evidence is nothing more than the introduction of the investigative techniques of law enforcement officers.  Every defendant has a right to be tried based on the evidence against him or her, not on the techniques utilized by law enforcement officers in investigating criminal activity.  Drug courier profile evidence is nothing more than the opinion of those officers conducting an investigation.  Although this information is valuable in helping drug agents to identify potential drug couriers, we denounce the use of this type of evidence as substantive evidence of a defendant’s innocence or guilt."25

Profiling in U.S. v. Mendenhall

The standard courts use to ensure that a stop is constitutionally sound is whether the agents had reasonable suspicion that the respondent engaged in wrongdoing when they encountered him or her.  The officer must be able to articulate something more than an "inchoate and unparticularized suspicion or ‘hunch.’"26 In this case, the Court held that there had been no seizure; therefore, it did not address the issue of whether the DEA agents had reasonable suspicion to stop the respondent.27 Here, the respondent arrived at the Detroit Airport on a flight from Los Angeles in the early morning and was the last one to get off the plane.28 The respondent was a 22-year-old African-American female who lacked a high school degree.29 After leaving the aircraft, the respondent walked to the baggage area and proceeded to an Eastern Airlines ticket counter to purchase a ticket to Pittsburgh.30 After she purchased the ticket, the two agents approached her, asked to see her airline ticket and identification, and discovered that the names on both did not match.31 Following this encounter, the agents asked the respondent to follow them to their office.32

Profiling in U.S. v. Sokolow

In this case, the Court concluded that in assessing whether a stop is valid, the court must consider the "totality of the circumstances—the whole picture."33 The Court noted that the agents must be able to articulate the factors involved, but if the factors articulated gave rise to a "profile," this would not detract from any evidentiary significance.34 The defendant had aroused the DEA agents’ suspicions because (1) he paid  $2,100 for two airplane tickets from a roll of $20 bills; (2) he traveled under a name that did not match the name under which the telephone number was listed (although it was later discovered the telephone number was his roommate’s); (3) his original destination, Miami, was a source city for illegal drugs; (4) he stayed in Miami for 48 hours, despite the fact that a round-trip flight from Honolulu to Miami takes 20 hours; (5) he appeared nervous; (6) he checked none of his luggage; and (7) he was wearing a black jumpsuit and gold jewelry.35

Daubert Analysis

Drug courier profiling poses an interesting question for analysis under Daubert. The key question rests on whether a conclusion qualifies as scientific knowledge, and this must be illustrated through sound scientific methodology. In these cases, the DEA agents were "experts" in the field and the Court effectively equated the agents’ training and past experience to scientific knowledge. However, past experience is subject to both arbitrariness and vagueness, and therefore should not be viewed as a "science."  Even if there are patterns that can be assessed that have assisted in creating the initial drug courier profiles, the element of human bias cannot be ignored or minimized when expertise is based on personal experience. Because of this inherent bias, it is difficult to ascertain whether appropriate controls can be implemented to ensure that drug courier profiles are not shaped by racism or socioeconomic factors.

Several studies have been conducted to measure the inherent racial bias that a police officer’s experience with crime can contain.  To illustrate, Jennifer Eberhardt, Philip Goff, Valerie Purdie, and Paul Davies administered an experiment to demonstrate the implicit racial bias police officers have with African-Americans and crime.36  When the police participants were subconsciously primed with an African-American male face, as opposed to a White male face or no prime at all, they were quicker to identify the faint outline of a weapon that emerged out of the visual static.37  This occurrence also happened in the reverse.  When participants were subliminally primed with drawings of weapons, they visually attended to African-American male faces more than White male faces.38  Essentially, these findings support the notion that African-Americans trigger the visual of weapons and make them easier to see, and at the same time, the idea of weapons trigger the visual attention to African-Americans.39  This may suggest that there is at least an association between African-Americans and weapons that could affect a police officer’s visual attention.40  Moreover, the visual attention did not necessarily indicate that the police officer was accurate.41  The officer was just more inclined to look more closely at the African-American faces, subliminally, to underscore the idea that this is inherent bias.42 Though this study used weapons rather than drugs as a stimulus, the key takeaway is that police officers can have an inherent bias that affiliates African-Americans and crime based on their personal experience.

Since drug courier profiles are widely used by DEA agents, such profiling would likely satisfy the Daubert prong of general admissibility. These cases did not reference empirical studies to support the DEA agents’ reasonable suspicions during the initial stops, so it is unknown whether there had been peer review or publication to support the profiling. Because of the holdings in this line of cases, it appears as though the Court would allow drug courier profiling to pass Daubert analysis, despite the fact profiling stems from personal partiality and experience.

Reactions from the Court

Justice Marshall’s dissent in Sokolow and Justice Powell’s concurrence in Mendenhall offer competing reasons for permitting or denying the use of drug courier profiling as evidence.  Justice Marshall’s dissent emphasizes his belief that the Court’s decision has diminished the right of all citizens to be secure in their persons.43 Justice Marshall construed the reasonable suspicion standard to be narrow to protect innocent persons from being subject to overbearing or harassing police conduct based on stereotypes or personal characteristics like race.44 He stressed that law enforcement officers must reasonably suspect that the person is engaging or poised to commit a criminal act at the moment they stop the individual.45 Justice Marshall also notes the dangers of permitting drug courier profiling on the basis of personal and behavioral traits because of its ability to dull the officers’ capacity to make sensitive and fact-specific inferences.46

On the other hand, Justice Powell’s concurrence in Mendenhall focuses on the public interest served by the seizure, the nature and scope of the intrusion, and the objective facts upon which the DEA agents relied.47 Specifically, Justice Powell states that the public has a compelling interest to detect drug traffickers who earn a hefty personal profit from the illegal conduct.48 Justice Powell also notes that the agent who stopped the respondent had ten years of experience and special training in drug enforcement in the Detroit Airport and had been involved in 100 drug-related arrests over the preceding year.49 Furthermore, Justice Powell weighs the respondent’s interest against the government’s interest and finds that the level of intrusion the respondent experienced was minimal in comparison to the harm of trafficking the heroin that she had concealed. Additionally, Justice Powell reminds his readers that while law enforcement officers do have the liberty to question anyone on the streets, the person being addressed has the equal right to ignore his or her interrogator and walk away.50

Overall, the Court has been both receptive and permissive towards DEA agents’ reliance on their training and past experience to create drug courier profiles and use them to stop and seize certain individuals.  Although there is an interest in preventing drug trafficking, there are dangers that arise when drug courier profiling crosses the line to racial profiling.

Drug Courier Profile Evidence in Other Cases

Despite the problematic nature of the drug courier profile, some courts have nonetheless upheld the admissibility of drug courier profile evidence in various circumstances.  In U.S. v. Beltran-Rios, the Court of Appeals for the Ninth Circuit upheld the use of drug courier profile testimony for impeachment purposes after the "defense counsel ‘opened the door’ to this line of questioning by emphasizing [the defendant’s] apparent poverty."51 In U.S. v. Gomez-Norena, the same Court of Appeals upheld the use of drug courier profile testimony as background material to explain how the arrest occurred.52 In U.S. v. Lui, this Court also noted, "[I]t may be appropriate to recognize a modus operandi exception [to the general exclusion of drug courier profile testimony] in certain cases, such as those involving complex drug-smuggling conspiracies."53 U.S. v. Dimas provides a recent example of the modus operandi exception in action.54 In that case, the defendant challenged the admission of a DEA special agent’s expert testimony regarding the general practices of drug traffickers, including an opinion that a notebook was a "pay ledger" commonly used in the drug trade, as improper drug courier profile evidence.  The Ninth Circuit sided with the government, finding that the "testimony helped explain [the defendant]’s modus operandi by describing how certain words and actions were consistent with the common practices of drug traffickers," and affirmed the district court’s judgment.55

U.S. v. Lim illustrates the high level of specificity a drug courier profile can (and often does) have.56 In Lim, undercover Honolulu police officers had been assigned the task of observing arriving passengers.  The defendant had just flown in from Los Angeles. The officers noticed another defendant, named Apostol, who walked off the plane before the defendant, look around the airport as if he were seeking someone. The officers then noticed the defendant walk off the plane, also appearing to look around for someone. The officers stopped Apostol and the defendant separately for questioning. Both consented to searches of their luggage. The officers did not find drugs or contraband in the defendant’s possession, but found methamphetamine in Apostol’s luggage.  The officers also found a flight itinerary in Apostol’s possession that referred to the defendant. Apostol told the officers that the drugs were not his but belonged to another passenger on the plane.  One of the officers asked Apostol if this passenger was wearing a yellow sweater (which the defendant was), and Apostol answered affirmatively. Both Apostol and the defendant were then arrested and indicted for conspiracy to distribute and to possess with intent to distribute methamphetamine. At Lim’s jury trial, one of the officers testified regarding the drug courier "shotgun" profile. The officer testified that a shotgun is a member of a drug conspiracy who travels with a "mule," who, in turn, carries the drugs. The shotgun does not carry drugs but accompanies the mule to ensure that all goes according to plan. The district court overruled the defendant’s objection to this testimony, but stated that it would not allow the officer to express an opinion to the jury that the defendant was a shotgun because he fit the profile and gave a limiting instruction to the jury. The defendant was found guilty and appealed on the basis of the admission of the drug courier shotgun evidence. The Ninth Circuit determined that "[t]he admission of drug courier profile evidence is inherently prejudicial to the defendant because the profile may suggest that innocuous events indicate criminal activity" and that "the profile …applied to two innocuous bits of evidence concerning [the defendant]—the fact that he was engaging in domestic travel and was not carrying drugs"—constituted an abuse of discretion.57 Given all of the evidence against the defendant, however, the Court held that the error was harmless.

An Examination of Drug Courier Profile Evidence in Law Review Articles

As William V. Conley notes in Mendenhall and Reid: The Drug Courier Profile and Investigative Stops, "[t]he actual characteristics which make up the profile have varied over the years and have also depended on the city in which the DEA agents are stationed."58 Conley highlights the following characteristics as common in profiling: traveling with little or no luggage; taking direct flights to and from specified cities, furnishing false information to airline personnel when asked for a telephone contact; and when two or more parties are involved, attempting to conceal the fact that they are together.59 Conley also cites the following characteristics as less frequent but also as having appeared in profiling: circuitous routes from known source cities (e.g., flying from Los Angeles to New Orleans by way of St. Louis); purchasing a one-way ticket; Hispanic origin (especially Mexicans); youth; luggage lacking identification tags; ticket purchases at the last minute or arriving for the flight at the last minute; early morning flights; and deplaning either first or last.60

In Race and the Decision to Detain a Suspect, Cornell Law School’s own Professor Sheri Lyn Johnson writes, "Although the DEA has refused to commit the entire [drug courier] profile to writing, the profile clearly contains a racial component."61 In Drug Courier Profiles: An Infringement on Fourth Amendment Rights, Irene Dey expands on this implication.62 Following the Sokolow decision, Dey notes that "profiles as they exist now allow officers to stop suspects based on the ‘totality of the circumstances’ as well as the officer’s own experiences."63 Therefore, Dey stresses that "[i]f, in the officer’s experience, drug couriers are of a certain ethnicity or racial background, that would be a sufficient component for the stop, [despite this being] strictly prohibited by the Equal Protection Clause."64

Profiling Studies and Suggestions

There "is embarrassingly little evidence of any kind to support the accuracy of drug courier profiles."65 Even profiling in general has produced few empirical studies evaluating the difference in the rates of stops and searches of minorities "to determine if profiling is discriminatory or truly an effective policing technique."66 Additionally, it is likely the DEA seeks to keep confidential some characteristics of the drug courier profile.67

In 1985, Morgan Cloud empirically tested the validity of the original drug courier profile first developed by Special Agent Markonni by reviewing all of the then-existing court opinions referring to the drug courier profile and tabulating the frequency with which certain characteristics appeared.68  Of the 15 characteristics studied, only 6 were present in over a third-of the cases and only 3 were present in over half of the cases.69  Although this study is likely outdated by now, its findings suggest that the original drug courier profile, which may have been the prototype for many subsequent profiles, was significantly flawed.

In 2004, another study addressed the various types of statistical methods used to evaluate profiling and came to the conclusion "that the proper method to use in evaluating profiling is to focus on the ‘find rate,’ which is the percentage of individuals who are stopped and searched and who are found to be engaging in criminal activity."70  If the find rate among a particular group is low compared with the other groups that are being stopped and searched, "then a disproportionate number of innocent people of that group are being stopped and searched."71  It does not appear, however, that such a "find rate"-based study has yet been conducted.  Another study that would be helpful in ascertaining the value of the drug courier profile, if it existed, is one that chronicled how much instruction or training the agents receive on drug courier profiles.

Expert Witnesses

As earlier noted, expert testimony regarding drug courier profiles is particularly problematic because the witnesses are the law enforcement agents themselves.  Because objective standards do not exist in the realm of drug courier profiling, this gives rise to serious reliability concerns.

The Bigger Picture

There are many similarities between the evidence at issue in drug courier profile cases and Floyd v. City of N.Y.   Both the drug courier profile cases discussed here and Floyd are "about the tension between liberty and public safety in the use of a proactive policing tool" involving stops.72 Therefore, both the drug courier profile cases and Floyd raise Fourth Amendment concerns.  Certain drug courier profile cases may also raise, like in Floyd, Fourteenth Amendment and Equal Protection Clause concerns.

Notably, both the drug courier profile cases and Floyd were based in part on "imperfect information" coming from authority figures.73 For example, in Floyd, the plaintiffs’ case was based on the aggregate information stored in the New York Police Department’s UF-250 database. A UF-250 is a form that police officers are required to prepare after each stop and is therefore flawed because it "only records the officer’s version of the story" and "permits the officer to merely check a series of boxes, rather than requiring the officer to explain the basis for [his or] her suspicion."74 Similarly, the petitioners in the drug courier profile cases largely built their complaints on challenges to the admissibility of expert testimony on drug courier profiles. This testimony is arguably more subjective than the flawed UF-250 forms because reasonable suspicion to stop is not based on purportedly objective, written criteria, but whatever the testifying officer believed based on the "totality of the circumstances" in which he perceived them to be.75

Footnote Sources:

1 U.S. Const. amend. IV.

2 See id.

3 Brinegar v. U.S., 338 U.S. 160, 183 (1949) (suggesting the possibility of varying degree of Fourth Amendment protection depending on the gravity of the offense).  Traditionally, the warrant requirement could only be excused through exigent circumstances, although the search or seizure still had to be supported by probable cause.  See Warden v. Hayden, 387 U.S. 294 (1967).  This exception became impracticable when law enforcement officers were faced with on-the-spot observations calling for swift action.  See Terry v. Ohio, 392 U.S. 1, 10 (1968).

4 Camara v. Municipal Court of the City and Cnty. of S.F., 387 U.S. 523, 536-37 (1967).

5 See id.

6 See Terry, 392 U.S., at 20-21.

7 See id. at 16.

8 Id. at 25.

9 See U.S.’s Petition for Certiorari at 2-3, U.S. v. Mendenhall, 446 U.S. 544 (1980).

10 See U.S. v. Ehlebracht, 693 F.2d 333, 335 (5th Cir. 1982) (identifying Markonni as the composer of the profile).

11 Thomas J. Andrews, Screening Travellers at the Airport to Prevent Hijacking: A New Challenge to the Unconstitutional Conditions Doctrine, 16 Ariz. L. Rev. 657, 712 (1974).

12 See id.

13 U.S. v. Albarado, 495 F.2d 799, 804 (2d Cir. 1974).  In 1969, there were thirty-three successful hijackings in the United States and forty unsuccessful attempts.  After the implementation of the FAA's program, these numbers fell to ten successful hijackings in 1972 and zero in 1973.

14 See U.S.’s Petition for Certiorari at 2, Mendenhall, 446 U.S.

15 Morgan Cloud, Search and Seizure by the Numbers: The Drug Courier Profile and Judicial Review of Investigative Formulas, 65 B.U.L. Rev. 843 (Nov. 1985).

16 U.S.’s Petition for Certiorari at 3, Mendenhall, 446 U.S.

17 Id.

18 The profile cases analyzed in this study are replete with descriptions of this procedure.  See e.g., Mendenhall, 446 U.S.; Florida v. Royer, 460 U.S. 491, 493-95 (1983); Reid v. Georgia, 448 U.S. 438, 439 (1980).  See also U.S. v. Bailey, 691 F.2d 1009, 1011-12 (11th Cir. 1982), cert. denied, 461 U.S. 933 (1983); U.S. v. Van Lewis, 409 F. Supp. 535, 538-39 (E.D. Mich. 1976), aff'd 556 F.2d 385 (6th Cir. 1977), cert. denied, 434 U.S. 1011 (1978).

19 See Schneckloth v. Bustamonte, 412 U.S. 218, 222 (1973).

20 Terry, 392 U.S articulates the Fourth Amendment classifications of police-citizen transactions.  These encounters are categorized as voluntary and therefore avoid Fourth Amendment implications; as "Terry stops," requiring reasonable suspicion that a crime is occurring; or as "full-blown arrests," requiring probable cause.  Id. at 27.

21 Cloud, supra note 15, at 848.

22 See, e.g., U.S. v. Buenaventura-Ariza, 615 F.2d 29, 31 (2d Cir. 1980) (Miami as an example of a source city); U.S. v. Price, 599 F.2d 494, 496 (2d Cir. 1979) (Chicago is a source city); U.S. v. Elmore, 595 F.2d 1036, 1037 (5th Cir. 1979) (Detroit is a source city); U.S. v. Andrews, 600 F.2d 563, 566 (6th Cir. 1979) (Los Angeles is a source city).

23 Charles L. Becton, The Drug Courier Profile: "All Seems Infected That Th' Infected Spy, as All Looks Yellow to the Jaundic'd Eye," 65 N.C. L. Rev. 417, 439 (1987); see also Florida v. Royer, 460 U.S. 491, 493 (1983) (paying for ticket in cash with small bills as an example of part of a drug courier profile).

24 U.S. v. Sokolow, 490 U.S. 1, 8 (1989).

25 U.S. v. Hernandez-Cuartas, 717 F.2d 552, 556 (11th Cir. 1991).

26 Terry, 392 U.S., at 27.

27 Mendenhall, 446 U.S., at 547.

28 Id. at 558.

29 Id. at 561.

30 Id.

31 Id.

32 Id.

33 Sokolow, 490 U.S., at 7.

34 Id. at 10.

35 Id. at 5.

36 Jerry Kang et al., Implicit Bias in the Courtroom, 59 UCLA L. Rev. 1124, 1132 (2012).

37 Id.

38 Id.

39 Id. at 1137.

40 Id.

41 Id.

42 Id.

43 Sokolow, 490 U.S., at 11.

44 Id.

45 Id.

46 Id.

47 Mendenhall, 446 U.S., at 561.

48 Id.

49 Id. at 564.

50 Id. at 552.

51 U.S. v. Beltran-Rios, 878 F.2d 1208, 1211 (9th Cir. 1989) ("[C]ounsel is trying to suggest to the jury that Beltran is not part of a smuggling operation because he lacks the accoutrements of wealth associated with such a profitable activity.  In light of this testimony, …the Government should have an opportunity to rebut the inference that defense counsel was trying to raise.").

52 U.S. v. Gomez-Norena, 908 F.2d 497, 501 (9th Cir. 1990) ("Here the government introduced Inspector Espinoza’s testimony not to prove that Gomez was guilty, but to provide the jury with a full and accurate portrayal of the events as they unfolded on that Friday afternoon.").

53 U.S. v. Lui, 941 F.2d 844, 848 (9th Cir. 1993).

54 U.S. v. Dimas, 532 Fed.Appx. 746 (9th Cir. 2013).

55 Id. at 748.

56 U.S. v. Lim, 984 F.2d 331 (9th Cir. 1993).

57 Id. at 334-35.

58 William V. Conley, Mendenhall and Reid: The Drug Courier Profile and Investigative Stops, 42 U. Pitt L. Rev 835 (Summer 1981).

59 Id. at 836, 838.

60 Id. at 838-39.; see Mendenhall, 446 U.S.

61 Sheri Lyn Johnson, Race and the Decision to Detain a Suspect, 93 Yale L.J. 214, 234 (1983).

62 See Irene Dey, Drug Courier Profiles: An Infringement on Fourth Amendment Rights, 28 U. Balt. L.F. 3, 8 (Summer 1998).

63 Id.

64 Id.

65 Scott L. Johnson, "The Self-Fulfilling Prophecy of Police Profiles," The System in Black and White: Exploring the Connections Between Race, Crime, and Justice 99-100 (Michael W. Markowitz & Delores D. Jones-Brown, eds., 2000).

66 Katrina W. Berger & Dee Wood Harper, Jr., "Relevant Laws and Empirical Research on Profiling in Law Enforcement in the United States," Strategic Responses to Crime: Thinking Locally, Acting Globally 201 (Melchor de Guzman, Aiedeo Mintie Das, & Dilip K. Das, eds., 2012).

67 Conley, supra note 33, at 839.

68 Markowitz et al., supra note 40, at 100.

69 Id.

70 Berger & Harper, supra note 60, at 201.

71 Id.

72 See Floyd v. City of N.Y., No. 08 Civ 1034 (S.D.N.Y. Aug 12, 2013).

73 See id.

74 Id.

75 See Sokolow, 490 U.S., at 8.