Speeding Isn’t a DUI Cue: What NHTSA Teaches Officers and How It Helps Your Defense
If you were pulled over for speeding and later charged with DUI in Tucson or Pima County, you might assume that the speeding was part of the reason the officer suspected you were impaired. But what many people don’t realize is that the National Highway Traffic Safety Administration (NHTSA) has done decades of research into how impaired drivers behave behind the wheel, and speeding doesn’t even make the list.
The NHTSA has developed a specific list of 20 cues that officers are trained to look for when identifying impaired drivers at night. These cues were developed through controlled studies and field research, and each one has a statistical correlation with a blood alcohol concentration (BAC) of 0.08% or higher. These are the very cues that officers rely on during their training and throughout their careers to justify DUI investigations. But despite its prevalence as a traffic violation, speeding simply didn’t make the cut.
So what are these 20 cues? Why were they chosen? And how can a defense attorney use the absence of speeding from this list to challenge the officer’s conclusions? If you’re facing a DUI charge in Tucson or elsewhere in Pima County, understanding the role of these cues—and their limits—could be key to your defense.
Understanding the 20 NHTSA Nighttime Cues of Impairment
The 20 cues were developed by NHTSA through observational research in the 1980s and 1990s. Field studies were conducted in various states to determine which driving behaviors most accurately predicted whether a driver was impaired. Officers were trained to document specific behaviors, and researchers later correlated those behaviors with BAC test results.
From that data, NHTSA compiled a list of behaviors that, when observed, gave an officer a statistically significant likelihood that the driver was at or above the legal limit. These 20 cues were grouped into four broad categories: problems with lane position, speed and braking issues, vigilance problems, and poor judgment.
Here are the categories and examples of behaviors:
Lane Position Problems:
Weaving or weaving across lane lines
Straddling a lane line
Drifting or swerving
Turning with a wide radius
Speed and Braking Problems:
Stopping too far, too short, or jerky stops
Unexplained acceleration or deceleration
Varying speed
Driving more than 10 mph below the limit
Vigilance Problems:
Driving without headlights at night
Failure to signal or inconsistent signaling
Driving in opposing lanes or the wrong direction
Slow response to traffic signals
Stopping inappropriately in traffic
Following too closely
Judgment Problems:
Making illegal or improper turns
Nearly striking objects or other vehicles
Engaging in unusual or inappropriate behavior
Having an appearance of impairment (e.g., slumped posture, flushed face)
What’s important to note here is that all of these behaviors have a demonstrated connection to the kind of divided attention, impaired judgment, and slowed response times that alcohol or drug impairment tends to cause. These are not just bad driving habits—they are specific, observable indicators that correlate with impairment.
So Where Is Speeding?
It isn’t there. Speeding is not one of the validated cues.
That surprises a lot of people. Intuitively, many assume that impaired drivers are more likely to speed. But NHTSA’s research revealed a different pattern. Impaired drivers are actually more likely to drive cautiously, overcompensate for their diminished abilities, and frequently drive below the speed limit. That doesn’t mean speeding never happens in DUI cases, but it wasn’t a statistically significant indicator of alcohol impairment in the studies that NHTSA conducted.
There are several reasons for this. Alcohol slows reaction time and clouds judgment. People who are intoxicated often become overly cautious, unsure of their surroundings, and hyper-aware that they might be doing something wrong. Rather than speeding, they brake too much, hesitate, or go too slow. These types of behaviors made the NHTSA list. Speeding did not.
What Officers Are Taught
During training, police officers are introduced to the NHTSA Standardized Field Sobriety Testing (SFST) curriculum, which includes these 20 nighttime cues. They are taught to observe driving behaviors before making a stop and to use these cues to establish reasonable suspicion that a driver may be impaired.
In theory, officers should be initiating DUI investigations only when they observe one or more of these validated behaviors. Of course, in practice, stops can be made for any traffic violation, including speeding, and officers may choose to investigate further if they suspect impairment. But the fact remains that speeding is not part of the NHTSA’s scientifically validated list.
This matters because NHTSA’s list is the foundation for DUI detection training. If an officer didn’t observe any validated cues prior to stopping you, that fact can become important later in court. It goes to the question of whether the officer had reasonable suspicion to begin a DUI investigation in the first place.
How This Plays Out in Court
Let’s say you were pulled over for going 10 miles over the speed limit at night. The officer claims you were speeding, and then, after the stop, noticed signs of impairment and conducted field sobriety tests.
As your defense attorney, I would ask:
Did the officer observe weaving, swerving, or drifting?
Was there any braking irregularity or difficulty maintaining lane position?
Did the officer see anything from the NHTSA list?
If the answer is no, and the only reason for the stop was speeding, that weakens the foundation of the DUI investigation. It may not invalidate the stop itself—speeding is a valid reason to initiate a traffic stop—but it opens the door to arguments that there was no objective basis to suspect impairment.
The field sobriety tests, toxicology results, and officer testimony all stem from the initial stop. If that stop wasn’t based on a reliable cue of impairment, it casts doubt on the officer’s judgment and the strength of the case overall.
Reasonable Doubt and the Role of the Defense
In any criminal case, the prosecution must prove guilt beyond a reasonable doubt. That includes not just proving that you were impaired, but that the officer had a valid reason to suspect impairment in the first place. If the entire case is built on a speeding stop with no corroborating indicators of DUI, there may be enough doubt to challenge the arrest, the investigation, or even the admissibility of certain evidence.
Defense attorneys in Tucson and throughout Pima County often use the NHTSA materials to cross-examine officers and challenge the legitimacy of the stop. We may argue that the officer lacked training, misapplied the cues, or drew conclusions not supported by science. When speeding is the only reason for the stop, we can contrast that fact with the very training materials the officer was supposed to follow.
Why This Matters in Tucson DUI Cases
If you’ve been charged with DUI in Tucson, your defense should start with a close look at the stop itself. As a DUI attorney who handles cases throughout Pima County, I know how frequently these cases hinge on a small detail—like whether the officer actually saw a validated cue of impairment.
Speeding may justify a traffic stop, but it does not, by itself, justify a DUI investigation. When an officer builds their suspicion on a factor that the science doesn’t support, it weakens their case. As your defense attorney, I use that weakness to your advantage.
Every DUI case is unique. But one thing is always true: a thorough understanding of the law, the science, and the training officers receive is essential to building a strong defense. If you’re facing DUI charges and the stop was based on speeding, that detail could be more important than you think.
Charged with DUI After a Speeding Stop? Let’s Talk.
I represent clients charged with DUI in Tucson, Pima County Justice Court, and surrounding areas. If you were pulled over for speeding and ended up in handcuffs, don’t assume the case is open and shut. There may be a defense rooted in the officer’s own training materials.
Reach out today to schedule a consultation. Let’s review your case and see if the stop, the investigation, or the evidence can be challenged.
