DWI investigations: Officers can enhance their interdiction skills starting with ‘vehicle in motion’ observations

Watching for the little things, patience pays off when building a solid case

This is the first article in a series that focuses on tips, techniques and methods front-line officers can use to improve their intoxicated driving interdiction abilities.

Nearly 40 years ago the anti-drunk driving organization known as Mothers Against Drunk Driving (MADD) was formed with the goal to stop drunk driving. The organization came about at a time when driving under the influence was spiraling out of control. Over the past four decades, MADD has been profoundly influential in raising awareness, campaigning for stiffer penalties and curbing DUI overall.

Unfortunately, this problem still plagues the United States today. As cops, we know that DWIs/DUIs/OWIs are some of the most viciously defended charges, and there is a large market for defense attorneys in this arena.

In our efforts as law enforcement to recognize and interdict impaired driving, standardized field sobriety tests (SFSTs) are the universal metric used nationwide to determine legal impairment. In my experience, however, I find that officers tend to put too much stock in SFSTs solely and neglect other aspects of the investigation. I hope to counter that with this set of articles.

If you think you may have an impaired driver, do not be too quick to effect the stop.
If you think you may have an impaired driver, do not be too quick to effect the stop. (Photo/Getty Images)

In this series, I will explore several tips, techniques and methods front-line officers can use to improve their investigative ability regarding intoxication crimes. For simplicity, we will refer to these crimes as DWIs collectively.

Before we get started, I want to highlight something I believe is important, and that is the notion of abandoning “drunk” from your mind and lexicon and replacing it, instead, with “impairment” and/or “intoxication.” The reason for this is because drivers with mono-drug and poly-drug impairment have become increasingly prevalent in modern times.

If you focus your efforts on “drunk,” you may rush to judgment and miss other indicators of impairment. Later in the series, we’ll discuss alcohol versus drug impairment. Impairment in general can have several causes, and in the end, our focus is getting unsafe drivers off the roadway. Let us start with the beginning of any intoxication investigation: vehicle in motion.


Found within the SFST Student Manual, the National Highway Traffic Safety Administration (NHTSA) provides a total of 24 driving cues along with 10 post-stop cues that represent a probability of impairment or intoxication. The listed cues are bread-and-butter stuff but not all-inclusive.

Good detection comes from good observation. Keep your eyes open for any behaviors that stand out or draw your attention – anything that makes you say, “Hmm, that’s odd!” In my experience, small, subtle behaviors pique my curiosity.

For example, imagine you are following a vehicle around a curve in the roadway; watch to see if the vehicle begins to negotiate the curve prematurely or too late, and continue to watch while the vehicle is exiting the curve. This is an example of vigilance problems. This behavior by itself does not automatically mean you have an intoxicated driver, but it is an example of things to look for.


If you think you may have an impaired driver, do not be too quick to effect the stop. Instead, if it is safe to do so, follow them a bit to observe additional indicators, which allows you to fundamentally begin building the case for DWI.

The more violations or behaviors observed, the more likely your suspicion of impairment is confirmed. Also, the more you can articulate those observations, the less likely any challenge in court regarding your reason for contact will be successful. If your vehicle is equipped with video, begin recording your observations but do not dictate them to the camera. Make note of all observations made from the initial sighting to the moment the vehicle comes to a stop and articulate them in your report.

Defense attorneys will attempt to dismantle your case fact by fact, piece by piece to convince a jury. Meanwhile, you are trying to convince the jury that based on the totality of the circumstances, the opinion you formed regarding intoxication was correct. There is no such thing as having too many facts or too much ammunition for your case, and it starts with the vehicle in motion.


Try to avoid falling into the trap of “probable cause only.” The burden of proof needed to conduct a stop and investigate further is reasonable suspicion, not probable cause. When it comes to being dispatched to a possible intoxicated driver that was called in, I often hear about officers who get behind the vehicle and “look for a violation.”

If this is you, stop doing it! There is well-established law regarding these situations. As a general rule-of-thumb, if a layperson believes someone may be intoxicated and they call the police, then reasonable suspicion has been established by that fact alone.

In these cases, make sure, though, to have dispatch adequately identify the caller because you will probably need them to testify in court about their observations. Now, as previously mentioned, it is never a bad idea to follow and monitor if it is safe to do so. I encourage you to get with your local prosecutors and discuss the contents of this paragraph with them.


Sometimes we are unable to see the vehicle in motion and must rely on other methods to “wheel the driver.” For example, you may respond to a vehicle crash and your suspect may deny having driven and no other witness can place him behind the wheel of the vehicle. Use what you have and try to build the case by checking things like the position of the driver seat. Is it too long or short compared to your suspect’s height?

Does the suspect have any injuries that you may find evidence of on the steering wheel, dashboard or windshield? Is the driver seatbelt locked in place and, if so, does your suspect have imprints or markings on their clothing or skin from the tensioned seatbelt? Think outside the box, get creative and remember to articulate all of it later.

In the next article of the series, we will look at different methods to further enhance your investigation during the "personal contact" phase. Click here.

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