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Back to Archives | Back to July 2007 Contents 

Bridging the Legal Gap between the Traffic Stop and Criminal Investigation

Richard J. Ashton, Chief of Police (Retired), Frederick, Maryland, and Grant/Technical Management Manager, International Association of Chiefs of Police, Alexandria, Virginia

raffic law enforcement regularly identifies those who have perpetrated—or who intend to commit—serious criminal acts. Four of the September 11 terrorists were issued speeding citations just before that infamous day,1 and those 19 terrorists had obtained a total of 34 driver’s licenses and identity cards.2 Since its inception in 1998, 3M’s annual Looking Beyond the License Plate awards program has showcased representative examples of the excellent police work that has evolved from countless daily traffic stops. Registration irregularities contributed to Timothy J. McVeigh’s apprehension just 75 minutes after the 1995 bombing of the Murrah Federal Building in Oklahoma City,3 as well as to the 2002 arrest of a Utah driver with two corpses in his vehicle’s trunk as he was en route to commit a third murder; to the 2002 seizure of Washington, D.C., snipers John A. Muhammad and John L. Malvo; to the 2005 safe recovery in Tennessee of two children who had been abducted by their father from Washington state two years earlier; and to the 2005 capture of one of Virginia’s “10 Most Wanted,” who was being sought for violating parole in conjunction with a 1994 second-degree murder conviction.

Realizing that vehicles are involved to some degree in virtually every crime committed, police chiefs wisely encourage their officers to employ traffic law enforcement at every opportunity to make roadways and communities safer and to detect other criminal activities. Clearly, it is no accident that national safety belt use stands at 81 percent.4 However, even today the noncompliance rate is significant: 55 percent of passenger vehicle occupants killed in both 2004 and 2005 were not restrained, and 64 percent of those occupants killed during nighttime hours —compared with 47 percent during the day—were unrestrained in 2005.5

Competent and dedicated police officers legitimately detect anomalies during traffic stops and alertly “connect the dots” to solve more serious crimes. Virtually every level of law enforcement acknowledges the significance of traffic stops, but the judiciary rightly suppresses evidence obtained by officers who have not been trained properly in the legal intricacies of criminal interdiction and consequently are unable to bridge the legal gap between the initial traffic stop phase and the criminal investigation phase. Successfully bridging the gap between phases is not difficult, but it is absolutely vital for victory in court.

Step One: The Good Traffic Stop

At the foundation of many successful interdiction strategies is the legitimate traffic stop, which is based either on articulable and reasonable suspicion6 or on probable cause.7 There are many violations for which to initiate a traffic stop, but the more concretely identifiable the driving behavior for which a stop is made, the less susceptible it will be to attack during cross-examination, especially when an officer comes upon a treasure trove of drugs. Examples of such identifiable behavior (although their illegality may vary by state) follow:

  • Exhibiting driving behavior indicative of impaired driving

  • Failing to use safety belts in any of the 24 states that have enacted primary safety belt laws, or failing to place youngsters in child safety seats or in other appropriate occupant restraints

  • Failing to display a valid sticker on a vehicle’s registration plate, or to display two registration plates in states requiring the display of two

  • Operating a vehicle with a cracked windshield, without an illuminated headlight or tag light, or with another safety equipment defect

  • Passing through a red light or stop sign without stopping

  • Speeding

  • Using “registration plate covers” to conceal or distort characters8

This last behavior is an example of a violation that would allow an officer to prolong legitimately the initial traffic stop phase, for in this instance, the officer can seize the cover as a tool of the crime. This accomplishes two objectives. The first objective is to actually remove the cover, since there is no guarantee that a citation or a warning would make this happen. Second, it permits longer contact with the driver and provides more time for a canine unit to arrive and conduct an exterior check for contraband. A traffic stop cannot be lawfully extended merely to await the appearance of a canine unit. Whether or not required by law, an officer who is able to testify to the consistent use of this or any similar practice may experience less consternation when testifying.

Simply put, an officer may initiate during a traffic stop only those activities related to the purpose of that stop and must “diligently pursue” them.9 In order to determine whether a traffic stop is reasonable under the Fourth Amendment, a two-pronged inquiry must be undertaken to evaluate “whether the officer’s action was justified at its inception, and whether it was reasonably related in scope to the circumstances which justified the interference in the first place,”10 e.g., “[a] seizure that is justified solely by the interest in issuing a warning ticket to the driver can become unlawful if it is prolonged beyond the time reasonably required to complete that mission. . . .”11

Pretextual Stops

There is nothing improper about making a valid traffic stop for one violation in order to investigate another, unless it “is based solely on the officer’s prejudice concerning a person’s race, ethnicity, sex, or similar distinction.”12 In Whren v. United States,13 the U.S. Supreme Court affirmed the holding of the U.S. Court of Appeals for the District of Columbia Circuit: “‘[R]egardless of whether a police officer subjectively believes that the occupants of an automobile may be engaging in some other illegal behavior, a traffic stop is permissible as long as a reasonable officer in the same circumstances could have stopped the car for the suspected traffic violation.’ 53 F.3d 371, 374–375 (CADC 1995). . . .”14 It reaffirmed these pretextual stops in Devenpeck v. Alford: “[A]n arresting officer’s state of mind (except for the facts that he knows) is irrelevant to the existence of probable cause. . . . That is to say, his subjective reason for making the arrest need not be the criminal offense as to which the known facts provide probable cause. . . .”115

No Time Limit Imposed, but Diligence Demanded

There neither is an established length of time—a “bright line” rule—within which a traffic stop must be completed,16 nor is there any prohibition against an officer undertaking simultaneously more than one legitimate purpose, as long as the officer actively is working toward completing the activities warranted by the initial stop.17 “In assessing whether a detention is too long in duration to be justified as an investigative stop, we [the Supreme Court] consider it appropriate to examine whether the police diligently pursued a means of investigation that was likely to confirm or dispel their suspicions quickly, during which time it was necessary to detain the defendant. . . .” (citations omitted).18

Careful documentation of every aspect of a stop is critical to successful prosecution. For example, a 32-minute traffic stop for displaying a registration plate cover that obscured the validation sticker was upheld in light of a Maryland state trooper’s inability to obtain verification—due to computer difficulties—of the status of the driver’s licenses of the operator and passenger and of the vehicle’s registration before the canine unit was alerted.19 Although the trooper had completed the written warning for the violation, he nevertheless delayed issuing it because the results of the computer checks had not yet been received. Even though the stop was captured on the in-car camera, the trooper meticulously testified to the times and contents of his seven unsuccessful attempts—via both radio and cellular telephone—to obtain from two different state police barracks the outcome of the checks he had requested. Maryland’s appellate courts emphasized that the trooper had exercised “reasonable diligence,” that the canine unit was alerted during the course of the initial traffic stop,20 and that it had provided the probable cause necessary to initiate a Carroll Doctrine21 search of the vehicle,22 discovering more than 2,100 grams of cocaine.

Permissible Actions

An officer stopping a driver, say, for exceeding the posted speed limit, may initiate a computer check for outstanding warrants, investigate the driver’s sobriety and license status, establish that the vehicle is properly registered and has not been reported stolen,23 and issue a traffic citation or warning. This initial traffic stop phase may be extended into the criminal investigation phase only if either (1) the driver consents to the continuing intrusion or (2) the officer develops during the first phase independent articulable and reasonable suspicion or probable cause to detain the driver longer. Judge Charles E. Moylan Jr., of the Maryland Court of Special Appeals, summed up this issue most succinctly in State v. Ofori:

One scenario, and one big chunk of the case law, is that in which the traffic stop provides the only justification for any Fourth Amendment detention. How long may it last, while the dog is on the way? The basic rule is easy to articulate. Once the traffic-related purpose of the stop has been served, any detention based on the traffic stop should terminate and the stopee should be permitted to leave the scene immediately. Once a traffic stop is over, there is no waiting for the arrival, even the imminent arrival, of the K-9 unit. . . .24

However, if a canine unit arrives during that period of time that the officer genuinely requires to accomplish the legitimate activities corresponding with the original purpose of the traffic stop, the canine can scan the stopped vehicle, for it is not a search.25 “A dog sniff conducted during a concededly lawful traffic stop that reveals no information other than the location of a substance that no individual has any right to possess does not violate the Fourth Amendment.”26 In this vein,

[a] “canine sniff” by a well-trained narcotics detection dog . . . does not require opening the luggage. It does not expose noncontraband items that otherwise would remain hidden from public view, as does, for example, an officer’s rummaging through the contents of the luggage. Thus, the manner in which information is obtained through this investigative technique is much less intrusive than a typical search. Moreover, the sniff discloses only the presence or absence of narcotics, a contraband item. Thus, despite the fact that the sniff tells the authorities something about the contents of the luggage, the information obtained is limited. This limited disclosure also ensures that the owner of the property is not subjected to the embarrassment and inconvenience entailed in less discriminate and more intrusive investigative methods.27

The Terry-Stop for Drugs

Significantly, if the initial stop is made on the basis of articulable and reasonable suspicion of a drug violation, an officer may await the arrival of a canine, for “[i]n a Terry-stop for drugs, dog sniffing is . . . a highly favored investigative modality. The prime purpose of a Terry-stop is to confirm or dispel the initial suspicion. . . .”28 Judge Moylan explains:

Nothing so well symbolizes the difference between a traffic stop and a Terry-stop for drugs as their respective attitudes toward the presence of drug-sniffing dogs. The dog has no role to play in a traffic stop. The dog may be the star performer in a Terry-stop for drugs. The traffic stop, once completed, will not await the arrival of the dog for so much as 30 seconds. The Terry-stop for drugs very deliberately and patiently does await the arrival of the dog. The dog’s arrival is, indeed, the primary reason for waiting.29

Step Two: The Criminal Investigation Phase

An officer can travel either of two bridges between the initial traffic stop phase and the criminal investigation phase: (1) independent articulable and reasonable suspicion or probable cause upon which to detain the driver longer, or (2) consent to interact further.

Clearly, “stopping an automobile and detaining its occupants constitute a ‘seizure’ within the meaning of those [the Fourth and Fourteenth] Amendments, even though the purpose of the stop is limited and the resulting detention quite brief. . . .”30 On the one hand, “[t]he case law universally recognizes the possibility that by the time a legitimate detention for a traffic stop has come to an end, or more frequently while the legitimate traffic stop is still in progress, justification may develop for a second and independent detention. . .”31

Aside from undertaking a probable-cause search of a vehicle on the basis of a canine alert occurring during the initial traffic stop phase, other scenarios permit the extension of that phase. For example, an officer who stops a vehicle for exceeding the posted speed limit can evaluate the driver’s sobriety—while awaiting the results of computer checks for warrants, as well as for license and vehicle statuses, and while preparing a citation or warning—and can administer field sobriety tests on the basis of independent articulable and reasonable suspicion developed during the initial traffic stop phase that the driver is under the influence of alcohol.32

Additionally, a computer “hit” indicating the existence of an active arrest warrant for the driver or signifying the suspension of the operator’s license provides probable cause for extending the initial traffic stop phase. Finally, the officer’s recognition of the driver during the initial traffic stop phase as the individual named in a “wanted flyer” generated by another law enforcement agency in connection with a felony provides independent articulable and reasonable suspicion to prolong the initial traffic stop phase until the officer “pose[s] questions, . . . inform[s] the suspect that the [other police agency] wished to question him[,]” and determines whether or not an arrest warrant is outstanding.33

The Consensual Encounter

On the other hand, if the officer completes the initial traffic stop phase and chooses to attempt to extend that phase by gaining the driver’s consent to interact further, the officer must avoid moving “seamlessly” between the initial traffic stop phase and the criminal investigation phase,34 i.e., between the seizure and the consensual encounter; the more distinct the break between the two, the easier it will be for the officer to show that the driver was free to leave.35 The constitutional standard for determining a seizure is, on the basis of the totality of the circumstances, “whether the police conduct would have communicated to a reasonable person that the person was not free to decline the officers’ requests or otherwise terminate the encounter. . . .”36 Put another way, would the police conduct “have communicated to a reasonable person that he was not at liberty to ignore the police presence and go about his business”?37

Although most citizens will accede to an officer’s request when they are not advised they are free to decline that request, their apparent willingness to do so should not be equated with their consenting to do so.38 For example, the vast amount of information currently at an officer’s fingertips ironically could pose legal problems for the officer. Many pre-Terry39 consensual encounters simply involved an officer’s skillful interview of a person primarily to ascertain the person’s identity and to discover illicit activity; they either matured into seizures, or they dissipated where articulable and reasonable suspicion or probable cause never developed or where the person approached merely went about his or her business. However, with today’s immediate access to the National Crime Information Center (NCIC) of the Federal Bureau of Investigation (FBI) and myriad other databases, an officer still may approach and talk to any person who chooses to listen and/or respond, but the officer’s encouraging that person to remain while awaiting the results of a computer check “during which there is no meaningful interaction between the citizen and police is more indicative of an involuntary rather than a voluntary encounter. . . .” (emphasis added).40Mendenhall establishes that the test for existence of a ‘show of authority’ is an objective one: not whether the citizen perceived that he was being ordered to restrict his movement, but whether the officer’s words and actions would have conveyed that to a reasonable person. . . .”41 The following scenario illustrates the ease with which an initially consensual encounter can quickly become an illegal seizure, one against which an officer constantly must guard:

That appellant felt obliged to remain until the warrant check had been completed is reinforced by the fact that the initial accosting in which he was asked his name and date of birth could not have taken more than a minute, followed by a five-minute delay. He thereafter was obliged to wait without any further meaningful interchange between himself and the officers. Detective Coleman testified: “Like I said, I was on my radio [sic] we were calling in. But he was just standing there. All three of us were standing on the sidewalk.”42 (emphasis added)

Even though there is no constitutional requirement43 to advise the driver that he or she is “free to go” in order to ensure the voluntariness of a consensual search,44 the officer who so notifies the driver—prior to the latter’s agreeing to the requested search—certainly bolsters the officer’s claim that the consent was voluntarily given.

Remember, too, that securing the driver’s consent to continue the stop—regardless of how voluntary the officer believes that consent was—will still give rise to serious prosecutorial difficulty, if the officer, intentionally or not, retains the operator’s driver’s license and/or the vehicle’s registration card or fails to provide the driver beforehand with a copy of the traffic citation or warning.

Chiefs recognize that “[e]ffective policing today requires the use of strategies to intervene in criminal activity before it is successfully undertaken[.]”45 The traffic stop is one such effective means by which to tackle criminal behavior, while at the same time ensuring the safety of highway users. Once officers learn to bridge the legal gap between the initial traffic stop phase and the criminal investigation phase, desirable results will accrue.■

1Robert S. Mueller III, “Partnership and Prevention: The FBI’s Role in Homeland Security,” April 19, 2002, FBI Major Executive Speeches,, May 7, 2005.
2Douglas Waller, “Inside The New Spy Bill,” Time, December 17, 2004,,9171,1009740,00.html, May 4, 2005.
3Taran Provost, “McVeigh Prosecutors Begin to Present Evidence,” Time, April 28, 1997,,8599,8044,00.html, May 31, 2007.
4Rae Tyson, “U.S. DOT Announces 2006 Seat Belt and Motorcycle Helmet Use Statistics,” NHTSA Press Release 13-06, November 28, 2006, NHTSA Press Releases 2006, May 18, 2007.
5NHTSA’s National Center for Statistics and Analysis, Motor Vehicle Traffic Crash Fatality Counts and Estimates of People Injured for 2005, updated December 13, 2006,, May 18, 2007.
6See IACP National Law Enforcement Policy Center, Model Policy: Motor Vehicle Stops, December 2006,, May 18, 2007, 1:
Reasonable Suspicion: In the present context, the totality of the circumstances in each incident or situation that provides an officer with a particularized and objective basis for suspecting legal wrongdoing. The process allows officers to draw on their own experience and specialized training to make inferences from and deductions about the cumulative information available to them. Reasonable suspicion is more than a hunch or feeling that an officer might have about an individual or circumstances. It is based on specific facts that, when taken together with rational inferences, reasonably warrant the vehicle stop.
Reasonable suspicion justifies a vehicular stop. But, in order to arrest the motorist, passengers, or both, the officer must establish probable cause.

7See Whren v. United States, 517 U.S. 806, 810 (1996) (citations omitted): “As a general matter, the decision to stop an automobile is reasonable where the police have probable cause to believe that a traffic violation has occurred. . .”
8Section 13-411.1 of the Maryland Vehicle Law.
9In United States v. Place, 462 U.S. 696 (1983), the Supreme Court uses the term “diligently pursue,” and in United States v. Sharpe, 470 U.S. 675 (1985), the Court uses the terms “diligently pursue,” “acted diligently,” and “diligently pursued” to refer to the manner in which officers should undertake investigative detentions.
10Sharpe, 470 U.S. at 682, quoting Terry v. Ohio, 392 U.S. 1, 20 (1968).
11Illinois v. Caballes, 543 U.S. 405 (2005) (slip. op. at 2).
12IACP National Law Enforcement Policy Center, Model Policy: Motor Vehicle Stops, 1. See also International Association of Chiefs of Police, “Bias-Based Enforcement,” part 20 in Highway Safety Desk Book, September 2004,, May 18, 2007; and International Association of Chiefs of Police, “Bias-Based Enforcement,” policy 1.26 in Manual of Police Traffic Services Policies and Procedures, July 2004,, May 18, 2007.
13Whren, 517 U.S. 806.
14Id. at 809.
15Devenpeck v. Alford, 543 U.S. 146 (2004) (slip op. at 6).
16Sharpe, 470 U.S. at 685.
17Charity v. State, 132 Md. App. 598, 614–615, cert. denied, 360 Md. 487 (2000): “We are not suggesting for a moment that when the police effectuate a traffic stop, they are operating under a ‘time gun’ or may not pursue two purposes essentially simultaneously, with each pursuit necessarily slowing down the other to some modest extent. We are simply saying that the purpose of the justifying traffic stop may not be conveniently or cynically forgotten and not taken up again until after an intervening narcotics investigation has been completed or has run a substantial course. The legitimating power of a traffic stop to justify a coincidental investigation has a finite ‘shelf life,’ even when the traffic stop . . . is not formally terminated.”
18Sharpe, 470 U.S. at 686.
19Byndloss v. State, 391 Md. 462 (2006).
20Id. at 479.
21Carroll v. United States, 267 U.S. 132 (1925).
22Florida v. Royer, 460 U.S. 491, 505–506 (1983); Wilkes v. State, 364 Md. 554, 586–587 (2001).
23United States v. Mendez, 118 F. 3d 1426, 1429 (10th Cir. 1997).
24State v. Ofori, 170 Md. App. 211, 235 (2006).
25Place, 462 U.S. at 707; Indianapolis v. Edmond, 531 U.S. 32, 40 (2000).
26Caballes, 543 U.S. at 410.
27Place, 462 U.S. at 707.
28Ofori, 170 Md. App. 211 (slip op. at 46 and 48–49): Nine federal and two state cases upholding detentions between 20 and 75 minutes in length pending the arrival of canine units are enumerated.
29Ofori, 170 Md. App. 211 (slip op. at 45).
30Delaware v. Prouse, 440 U.S. 648, 653 (1979) (citations omitted).
31Ofori, 170 Md. App. 211 (slip op. at 38).
32Blasi v. State, 167 Md. App. 483, cert. denied, 393 Md. 245 (2006).
33United States v. Hensley, 469 U.S. 221, 234 (1985).
34Ferris v. State, 355 Md. 356, 378 (1999).
35See United States v. Mendenhall, 446 U.S. 544, 554 (1980): “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 citizen, or the use of language or tone of voice indicating that compliance with the officer’s request might be compelled. . . .” (citations omitted). Additional examples of such circumstances, as described in Michigan v. Chesternut, 486 U.S. 567, 575 (1988), would be “that the police activated a siren or flashers; or that they commanded respondent to halt, or displayed any weapons; or that they operated the [police] car in an aggressive manner to block respondent’s course or otherwise control the direction of the movement. . . .” (citation and footnote omitted).
Ferris, 355 Md. at 377, enumerates “certain factors as probative of whether a reasonable person would have felt free to leave. . . . These factors include: [1] the time and place of the encounter, [2] the number of officers present and whether they were uniformed, [3] whether the police removed the person to a different location or isolated him or her from others, [4] whether the person was informed that he or she was free to leave, [5] whether the police indicated that the person was suspected of a crime, [6] whether the police retained the person’s documents, and [7] whether the police exhibited threatening behavior or physical contact that would suggest to a reasonable person that he or she was not free to leave.” Graham v. State, 146 Md. App. 327, 387 (2002), added to this list of 7 another factor: [8] whether the lesser suspect was detained (“From the detentionary status of that lesser suspect, we may draw a de novo inference as to the detentionary status of the greater suspect”).
36Florida v. Bostick, 501 U.S. 429, 439 (1991).
37Chesternut, 486 U.S. at 569.
38INS v. Delgado, 466 U.S. 210, 216 (1984).
39Terry, 392 U.S. 1.
40Reynolds v. State, 130 Md. App. 304, 335 (1999), cert. denied, 358 Md. 383 (2000), and cert. denied, 531 U.S. 874 (2000).
41California v. Hodari D., 499 U.S. 621, 628 (1991). By “Mendenhall” is meant Mendenhall, 446 U.S. 544.
42Reynolds, 130 Md. App. at 338 (1999), cert. denied, 358 Md. 383, and cert. denied, 531 U.S. 874 (2000).
43See Schneckloth v. Bustamonte, 412 U.S. 218, 227 (1973): “While knowledge of the right to refuse consent is one factor to be taken into account, the government need not establish such knowledge as the sine qua non of an effective consent. . . ”
44Ohio v. Robinette, 519 U.S. 33, 35 (1996).
45Michael J. Bulzomi, “Police Intervention Short of Arrest,” FBI Law Enforcement Bulletin 75, no. 11 (November 2006): 32.



From The Police Chief, vol. 74, no. 7, July 2007. Copyright held by the International Association of Chiefs of Police, 515 North Washington Street, Alexandria, VA 22314 USA.

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