DUI Investigations: The Vehicle In Motion Phase

Barnes & Fersten Law Firm

Barnes & Fersten Law Firm

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Police vehicle in motion

When it comes to DUI investigations, the first aspect that law enforcement officers focus on is called the “vehicle in motion” phase. This occurs while an officer is observing a driver on the road that they suspect of driving impaired, and involves looking for signs of intoxication such as weaving, swerving, or driving at inconsistent speeds. If an officer has seen enough to believe that the driver is impaired, they will initiate a traffic stop and proceed with further investigation.

The vehicle in motion phase is crucial because it can provide evidence of impairment that can be used against a driver in court. An experienced DUI attorney will be intimately familiar with the nuances of this phase and how to challenge the evidence gathered during it. In this blog post, we will discuss this first phase of a DUI investigation and the cues that may be indicative of impairment during the vehicle in motion or driving phase. Also, we will discuss common illegal stops that may result in your DUI case being dismissed or resolved favorably through negotiations.

I think I was illegally pulled over. What is required for a police officer to pull me over? 

With limited exceptions, an officer requires reasonable suspicion that you committed a traffic violation or criminal offense to blue light and pull you over. Reasonable suspicion requires the police officer to specify specific and articulable facts to believe a traffic or criminal act has occurred. Reasonable suspicion is a lower standard of proof than probable cause, which is what is required to place you in handcuffs and arrest you.

The 24 cues of DUI during the "Vehicle in Motion" phase

Not all traffic violations are indicative of impairment. Although an officer may blue light you and pull your vehicle over for moving or non-moving violations, any violation will suffice, certain moving violations are indicative of impairment. This means an officer may believe you are impaired based on your driving behavior alone. Police officers look for 1 of 24 possible cues of impairment during the first phase of a DUI investigation, the vehicle in motion, to use your driving behavior to allege you were impaired on the night of your arrest.

The following is a list of the 24 cues of impairment and the percentage that is associated with it predicts that a driver is above a .08 solely based on the cue of impairment:

  1. Problems Maintaining Proper Lane Position: 50-75%
    • Weaving
    • Weaving across lane violations
    • Straddling a lane line
    • Swerving
    • Turning with a wide radius
    • Drifting
    • Almost striking a vehicle or other object
  2. Speed and Braking Problems: 45-70%
    • Stopping problems (too far, too short, or too jerky)
    • Accelerating or decelerating for no apparent reason
    • Varying Speed
    • Slow Speed (10+ miles under the speed limit)
  3. Vigilance Problems: 55-65%
    • Driving in opposite lane or wrong way on one-way
    • Slow response to traffic signals
    • Slow or failure to respond to officer’s signals
    • Stopping in lane for no apparent reason
    • Drifting without headlights at night
    • Failure to signal or signal inconsistent with action
  4. Judgment Problems: 35-90%
    • Following too closely
    • Improper or unsafe lane change
    • Illegal or improper turn (too fast, jerky, sharp, etc.)
    • Driving on other than the designated roadway
    • Stopping inappropriately in response to officer
    • Inappropriate or unusual behavior (Throwing, arguing, etc.)
    • Appearing to be impaired

Although a non-moving or traffic violation not included on the list above would allow a police officer to pull you over, an officer should not have any preconceived notion that you are impaired if you did not exhibit one of the 24 cues listed above. Yet far too often police officers believe someone is impaired simply because of the location or time of night.

Speeding: For example, you will note that driving ten (10) miles or more below the speed limit is indicative of speeding but driving above the speed limit is not listed. Speeding, or driving above the speed limit, is not an indicator of impairment. In fact, the opposite can be argued to a prosecutor, judge, and jury. It is more difficult to speed and keep control of the vehicle, especially navigating turns than driving the speed limit; hence the reason for a speed limit in the first place because it is believed to be a safe speed to operate.

However, once again, speeding or another traffic offense that results in someone being pulled over can later result in an individual being charged and convicted of DUI based on cues that are observed during the traffic stop.

When does an officer commit an illegal traffic stop, and does it mean my DUI will be dismissed?

An officer commits an illegal traffic stop when the officer initiates his or her blue lights to pull a vehicle over without reasonable suspicion of a traffic violation. The attorneys at Barnes & Fersten have gotten DUI cases dismissed and resolved favorably through plea negotiations due to illegal traffic stops.

Looking at the 24 cues of impairment, you will notice that a handful of them are not traffic violations and therefore cannot be the reason for an officer blue-lighting you to pull you over. This is because some of the cues, even though indicative of impairment, are not against the law.

Weaving (within the lane): For example, “weaving” if within your lane of travel is not against the law and therefore does not provide an officer reasonable suspicion for a traffic stop. In fact, the Tennessee Supreme Court has ruled that being pulled over for weaving entirely within your lane of travel is not enough for an officer to pull you over and therefore it would be an illegal stop, without reasonable suspicion, causing your case to be subject to a suppression of the stop and dismissal of the case. Through a concept called “fruit of the poisonous tree,” everything after the illegal stop would be suppressed and therefore any blood or breath tests, field sobriety testing, and your interaction with the officer cannot be used against you if the stop got suppressed as an illegal stop.

Similarly, other cues such as accelerating for no reason, varying speed, and turning with a wide radius, among others, cannot be the basis for a police officer stopping your vehicle. Although it may used against you as a reason to believe you were impaired as a basis for the officer’s reasonable suspicion to conduct standardized field sobriety tests, combined with cues from phase 2, and it may be part of the officer’s basis for probable cause for an arrest, it is not a valid and legal basis for a traffic stop. Thus, your lawyer should argue the illegal stop to a prosecutor and potentially a judge at a preliminary hearing and/or motion to suppress hearing.

What are some exceptions to the reasonable suspicion requirement for a traffic stop?

In next week’s blog, we will discuss the three (3) primary exceptions to the reasonable suspicion requirement for a legal traffic stop, including:

  1. Sobriety checkpoints;
  2. Community caretaker; and
  3. Anonymous 911 calls.

The blog will detail the specific requirements for each of the three (3) exceptions, and some examples of when a DUI case may be dismissed or resolved favorably due to an officer not abiding by the specific requirements.

Attorney At Law, Managing Partner

Brandon D. Fersten is an esteemed Knoxville attorney practicing DUIcriminal defense, and juvenile law. Known for his empathetic approach and commitment to his clients, he brings a record of favorable case outcomes including dismissals and not guilty verdicts at jury trials resulting in Brandon being recognized as one of the “Top 40 Under 40” in Criminal Defense, U.S. News’ Best Lawyers: “Ones to Watch,” and Super Lawyers’ “Rising Stars”. Brandon’s professional accolades, combined with his passion for justice, position him as a reliable criminal defense advocate in the East Tennessee legal landscape.