DWI Corner
November-December 2008

Seven tips for trying one-witness DWI cases

Another misdemeanor DWI is set for trial—and it’s almost identical to the other 248 DWIs you have prosecuted. This article will remind you to present each case in court as though it were the first one you ever tried to keep your jury motivated and attentive.

Suzanne Jost

Assistant County Attorney in Kendall County

Not long ago, I successfully tried a run-of-the-mill DWI with a peace officer as my only witness. The defendant was a pleasant-looking older woman who dressed for court as though she were attending church. On the night of her arrest, she ran her truck into a yield sign, drove a few hundred yards down the road, and hoped that AAA arrived before the police noticed her. When it did not work out that way, she admitted drinking two Bud Lights with friends during a party at a retirement home.

The inventory of her vehicle included a partly-empty jug of Canadian Mist whiskey and nine full, cool-to-the-touch Dos Equis beers. In my small county, blood draw warrants are on my Christmas wish list but not yet available, so this traffic stop included standardized field sobriety tests, one of which she passed, and a defendant who agreed to blow into the Intoxilyzer, which malfunctioned. I didn’t have a breath test or a refusal on which to rely!

The evidence was not overwhelmingly strong. However, this woman looked intoxicated on the roadside video, with noticeable sways and a couple of instances of leaning on her truck for support. She also had a strong odor of alcohol, slurred speech, red and bloodshot eyes, and the inability to follow simple instructions. After she was arrested and read her Miranda rights, she repeated her “I had a couple of beers” story but also admitted that she and some friends consumed the whiskey. She never offered any explanation for why three bottles of Dos Equis were missing from the 12-pack.

To win this trial, I made the most of the available evidence and educated my jurors on all the intricacies of DWI detection—without putting them to sleep. My only witness, Officer Pete Moncada, testified with a lot of reiteration, repetition, and re-wording from me, and I presented several visual aids to reinforce my key points with the jury. Officer Moncada knows the law extremely well, is a good communicator, and does not show signs of nervousness, but he does not smile, relax, or appear completely comfortable on the witness stand. (Like most officers, he would much prefer to be out on the street than in a court of law.)

I focused my preparation in the following areas to maximize the circumstantial evidence in a one-witness DWI trial.


Prepare with the officer. First and foremost, the arresting officer must be invested in the trial’s outcome. Officers who care about our cases are absolutely essential to our success. The “false alarm” syndrome, where officers are routinely summoned to court and sit for docket call, only for a case to plead out, creates a false sense that they’ll never go to trial. Don’t let them get used to these false alarms! Instead, meet with them for each case.

Watching the in-car video together is indispensable for a number of reasons. First, your direct examination will be more conversational. Officers are stressed enough about testifying without being unfamiliar with or intimidated by the prosecutor. Second, you will both know the exact locations on the video that illustrate your important points. For example, if the officer noted observations of the defendant or her driving in his report, I make him show me on the video where each occurred so I can point them out to the jury. Third, watching the video gives the officer the opportunity to show where he made mistakes. We’ve probably all been hit in court by some unanticipated investigatory error, and it’s best to find these before defense counsel hands the officer his lunch on cross.

Finally, these conferences emphasize that the officers are the most important persuasive element during trial. Often, officers believe that the video does their job for them and that the jury will watch the video and understand the significance of what they see. Numerous times I have had officers tell me, “Well, I’m not exactly an expert.” Of course, I reply that it’s time to become one because that is what the State of Texas, judge, and jury expect of an officer as a trained administrator of the SFSTs. The officer must explain to the jury what his experience and training have taught him and make that expertise visible on the video.

If I have a less seasoned witness, I cover all the basics in this meeting. I discuss body language, eye contact, tone of voice, and reiterate that simply saying, “I do not know” is perfectly OK sometimes. I remind officers that they can always refer to their reports for details, and their training manuals should be used while on the stand, especially if the defense attorney is using one as a source for cross-examination. I also make it clear that the offense report and training manual are only “escape hatches” and that the officer should be able to tell the narrative of the arrest, all indicators of intoxication, and all instructions he gave the defendant without reference to the video or any reports.

Officer Moncada responded well. He reviewed the video before he and I met, and we watched it again together. This officer knew that each defense attorney has a particular style and strategy and came prepared with questions on what he could expect from the defense. I suggested that he take care not to sound argumentative, which is a difficult balance for officers: to show they are confident that they have made a correct assessment of intoxication while not appearing closed-minded or too quick to judge.


Be sure jurors can convict on a single witness’s testimony. Before starting the “one witness” line of voir dire questions, allow the jury to see that even without all the science that the trained and experienced officer applied to make this arrest, most regular citizens can pick out a drunk. Use a poster board to write veniremembers’ answers to this question: “What signs would you look for outside of this courtroom to know that a person is intoxicated?” Usually the jurors will say “stumbling,” “slurred speech,” and “smell of alcohol.” In this way, the jury creates a list of indicators of intoxication that the officer has seen in the defendant. Then I point out to the jury that those red flags do not require expertise, just common sense.

I continue by asking what the jury would like to see in a DWI trial to determine whether a defendant is guilty. I make a second list on the same chart as the list of red flags. These almost always include a videotape, an officer’s testimony, and a blood-alcohol concentration (BAC) level. I have never had any jury tell me during this line of questions that they would like a second officer or an eyewitness to the offense, even as they are making a wish list. By laying the situation out in this common-sense approach, the normal “one witness” situation in a DWI trial is not as insurmountable as with other types of offenses because your jury will see that the evidence presented in court is exactly what they asked for during voir dire.

Of course, prosecutors must also ferret out any jurors who distrust law enforcement or those who distrust evidence from a single witness. Those people may or not be swayed by the above demonstration, and prosecutors must find those jurors and ask questions for two purposes: to use a challenge if a particular juror cannot be unbiased toward law enforcement and to educate other jurors who might be hesitant to convict on the testimony of one person.

The “one-witness” line of questioning requires a prosecutor’s willingness to distinguish between two answers that sound similar but have opposite results under the law. The prosecutor should ask: “Imagine that each of you are sitting on a jury panel, and after hearing all of the evidence presented by the State, you are persuaded beyond a reasonable doubt of all of the elements we are required to prove. Is there anyone who would be unable to find a defendant guilty because the State called on only one person to testify?” Note that this question doesn’t say that all of the evidence came from one place because it didn’t (unless you don’t have a video or a refusal or a blow). It’s a subtle but important distinction.

Whether a prospective juror can be properly challenged for cause has to do with her stance on reasonable doubt. The caselaw in this area distinguishes between a juror who is holding the State to a higher burden than reasonable doubt (properly challengeable for cause) and a juror whose own personal version of reasonable doubt would never be met by one witness alone (not challengeable for cause). Any juror who holds the State to a standard of certainty is properly challengeable. Even if you can’t remove a juror for cause, use a peremptory strike if you still do not believe that juror could follow the law.

The most important distinction is to keep your hypothetical limited to the one-witness situation. The defense’s attempted rehabilition would include opening the door to the idea that more witnesses would allow more evidence to achieve proof beyond a reasonable doubt. However, the prosecutor must keep the jurors focused on the situation where there is only one witness and there is proof beyond a reasonable doubt in that juror’s mind.


Visual aids are essential. Because these trials don’t have victims a prosecutor can put on the stand to pull heartstrings, it is essential to give jurors something visually stimulating. Whether trial visuals are hand-drawn charts, professionally produced posters, or electronic PowerPoint presentations, they must be large and readable. These visual aids must also be in color or the jury will lose interest.

Up until recently, I had a number of reusable posters on hand so I didn’t have to reinvent the wheel for every DWI trial. (I admit that I copied them from TDCAA’s DWI Investigation and Prosecution book, which is available at www.tdcaa .com/publications. See pages 131-132, 145-147, 154, 161, and 175 of the book for the charts I used.) We added color and blew up the size; the words and layout in the book are clear, concise, and a perfect starting point. Since attending TDCAA’s recent training on digital evidence in the courtroom, I have replaced my paper charts with PowerPoints and hyperlinks. Either method serves the same purpose: keeping the jury motivated and interested in the trial.

If the defendant blew into the intoxilyzer, make a poster size version of the intoxilyzer slip. When the intoxilyzer operator testifies, get the slips admitted first, then ask to publish a large version so that as he is explaining what the different numbers mean, the jury can have a reference point. Don’t hesitate to add color or arrows for your jurors’ focus. Remember, this information is all new to them, and in-court demonstratives should not require inferences and should be memorable.

If the defendant did not provide a breath sample, use the DIC-24 instead. This paper is statutorily admissible and states explictly that the refusal will be used against the defendant. Blow up the area where this is explained along with the defendant’s signature. Also note that if the signature on the DIC-24 looks substantially different from the signature on the bonding sheet or any other signature given, blow that one up as well for a comparison. If a defendant’s normal signature is affected by alcohol, how could her driving not be?

Keep in mind while preparing a DWI case that jurors will remember what they see and hear much better than what they only hear. In addition to telling the jury that the defendant stumbled, fast-forward to the location of the stumble on the videotape and show it to the jury. If you have the capability, clip a video of the stumble and play it in court. I have had numerous DWI juries tell me that they do not even watch the video in the jury room because by the time the trial is over they have seen the tape three or four times, so make sure you show them all of the portions that illustrate the defendant’s intoxication while everyone is in the courtroom.

Maps are an easy way to get some color and interest into the officer’s testimony. In my small county, most of the road names that come up in testimony are obvious to jurors, but that won’t be the case everywhere. Also, when the officers use mile markers on the interstates or blocks of particular streets, they have an opportunity to show the jury exactly where this defendant was driving and what dangers lurked there for sober, defenseless drivers. Often, intoxicated drivers are lost when the officer stops them. When the map is shown in court, the defendant’s direction of travel is not even close to where she claimed to be headed. If a wreck occurred, show its exact location on the map.

In my Canadian Mist case, in addition to our maps, we pinpointed the spot on the videotape where the officer pulled the whiskey jug out of the defendant’s truck. He set it on the hood of his patrol car, along with the numerous unopened beer bottles. We also had video clips of the defendant’s multiple explanations for how much and what types of alcohol she drank. During direct examination, we reviewed the places where she noticeably swayed on tape and leaned on her truck for support.

One of my favorite pictures, which we showed in the PowerPoint presentation, was simply a Canadian Mist jug by itself. The officer testified that the amount missing from the jug in the defendant’s car was equal to nine shots of alcohol. During this testimony I left the jug up on the screen. I prepared another clip with nine whiskey glasses with liquor in them and two Bud Lights (the amount of beer the defendant admitted to drinking) to use in closing. Often, defendants are vague about their numbers by saying they drank “a couple of beers” or shared “some whiskey” with friends. Show the jury exactly what those vague amounts look like in actual liquid measure. If the defendant admitted to margaritas, put a picture of tequila in shot glasses on the screen to remind the jurors that the basis of drinks is not limeade and salt but rather hard liquor that makes for a dangerous driver. Use these visuals in closing while referring to your expert’s testimony, whether it was an officer or an intoxilyzer supervisor, about how long each shot takes to completely go through a person’s body.


Explain that the SFSTs are divided-attention tests. Many jurors have taught their own teenage sons and daughters how to drive, ridden with a bad driver, or cringed at other drivers talking on cell phones while behind the wheel. Anyone with a license understands that driving requires thinking about multiple things while performing intricate physical actions. Turning the steering wheel one inch can mean the difference between side-swiping or avoiding another vehicle; two seconds late on the brake can mean rear-ending another car. The jury will understand the concept of divided attention, and the prosecutor should repeat it often when discussing the SFSTs.

My clearest illustration of how divided attention is used in the sobriety tests is when the officer is instructing the suspect on how to perform the Walk-and-Turn test. I always watch this part of the video multiple times to see how best to use it in court. The test requires the suspect to stand heel-to-toe and balance while listening to a list of instructions—in other words, using mental and physical capacities at the same time. Usually, the defendant starts out in the correct stance. Then the officer begins the demonstration, and as the suspect concentrates on the officer’s directions, she falls out of the starting position. This fall is more than simply bad balance; it’s a failure to divide one’s attention between multiple tasks. Do not leave it to the jury to draw this inference on their own; explain to them in detail that no part of these tests is accidental or coincidental, and replay that part of the video during direct-examination to make that point.

Another behavior that happens routinely is the suspect fails to hold the starting position solidly but concentrates very hard to maintain her balance. These suspects miss most of the clues during the walking stage because they are focusing so hard on their balance that they ignore every instruction. Again, make this failure clear to the jury. The tests’ instructions are not complicated, especially when compared with all the motor and mental skills required for driving. Show the jury that someone who cannot stand on a straight line and listen to an officer talking at the same time has no business behind the wheel of a 2,000-pound car that requires reflexes and judgment to safely operate.

The best part about divided attention may lie in its scientific basis—yet the jury can understand it by applying common sense. With the prosecutor and officer’s in-court education on SFSTs, the jury will watch and judge the video not by a layperson’s standard but rather with the knowledge that safe driving requires multi-tasking, and these tests are gauging the defendant’s ability to do just that.

In my case, the defendant consistently argued that we could not prove that her intoxication caused the wreck. However, our maps showed that she was driving in the opposite direction from her home address and the video showed her repeatedly saying she was heading home from the party. Additionally, when I asked the officer about divided attention, we played the video through the Walk-and-Turn, and I re-wound it to replay the instruction phase where the defendant’s face was puckered in concentration. Then we counted the clues that showed she missed the officer’s simple instructions. During deliberations, the jurors did not watch the video at all and returned with a guilty verdict.


Remind jurors that sober people pass the SFSTs. Jurors are often (understandably) under the impression that every citizen given SFSTs is eventually arrested for DWI. While prosecutors and police officers know differently, it’s important to clarify that point for the jury.

The one question I ask every single officer in a DWI trial is whether drivers ever pass the SFSTs. (I do so because more than once, I’ve heard comments from spectators, lay persons, and defense attorneys who say, “Nobody could perform those tests even sober!”) The officer usually looks at me when answering like it’s a silly question and replies, “Of course”—as though any dummy would know that. That answer tells jurors in no uncertain terms that drivers who are pulled over for traffic violations but pass the SFSTs don’t end up in court—they drive themselves home safely, perhaps with a warning or ticket for the violation, but they are not under arrest for driving while intoxicated. You want the jury so well educated that they do not submit to the theory that the tests are impossible to pass.


Speak clearly and use common words. Don’t let the officer fall into law enforcement-speak, such as, “The vehicle was occupied three times” when he means that there were three people in the car. If the officer describes the “totality of the circumstances,” tell him to use more common words—”all the stuff that I knew at the time”—instead.

The same holds true for the testimony on Horizontal Gaze Nystagmus (HGN). Sometimes it’s the only scientific, objective, and arguably the most persuasive evidence that we present, so it especially requires careful and repeated explanation. If you have the previously mentioned posters or PowerPoints, HGN is the perfect topic to present using those methods.

Also prepare with the officer so that your questions do not confuse him and his answers do not confuse the jury. He should practice explaining HGN to the prosecutor and to a family member who has never read the NHTSA manual to see if his explanation is effective and understandable. If not, he should keep practicing until it is.

In my recent trial, the officer and I knew the HGN evidence would need explanation because this defendant had only four clues out of a possible six on the test. Even though her score is considered a failure and an indicator of intoxication, the officer had to practice explaining that a lack of the last two two clues was not evidence of sobriety. After trial, the jurors specifically told me that they were interested in the HGN testimony because it was new to them and the SFSTs were more objective than they realized. I have had multiple juries state similar opinions on their newly acquired knowledge of DWI investigations. If the HGN is the only science we have, our “‘CSI’ standard” requires that we use it as effectively as possible.


Empower the jury to protect the community from intoxicated drivers. Even if this is your 145th DWI trial, it is likely your jurors’ first participation in the criminal process. These citizens have completely rearranged job duties, daycare, and perhaps travel plans to perform their civic duty as jurors; they show up in county court and see what appears to be an average-looking Jane in the defendant’s chair. Help these good folks understand that even cases that don’t make compelling scripts for “Law and Order” are prosecuted for good reason.

The voir dire process is your chance to begin to remind the jury that rules of the road are important to follow for everyone’s safety. Closing argument is when you get to hand the torch to your jury. Charge the jury with the responsibility to hold normal, everyday people accountable for judgment so poor it amounts to a dangerous crime. In my quaint and touristy community, I always remind my jurors that a defendant being “very sorry” at trial does not neutralize her committing a crime. Likewise, the fact that a proactive officer stopped the defendant’s car and arrested her before anyone was injured does not lessen the defendant’s dangerous behavior.

One voir dire hypothetical that starts this ball rolling involves the differentiation between a DWI with no collision, a DWI with a one-car wreck, and a DWI with a death. I ask potential jurors to describe a driver with all of the clues of intoxication that the jury offered on the chart I spoke of earlier. I then ask what is the difference between that driver ending up as a DWI defendant versus an intoxication manslaughter defendant? Ask the jury if that driver took any precautions to make sure her intoxication did not endanger anyone else. Of course, the answer is “no.” The only difference between the two crimes works in the State’s favor in two important ways: First, if the defendant had a wreck and no one else was injured or affected, it was just blind luck. Second, if your defendant was stopped before she caused a wreck, it was solely thanks to the diligent efforts of law enforcement—at least the officer stopped her before she hurt somebody. Allow your jury to see equal culpability in the acts of the defendant in either scenario.


Misdemeanor DWI trials require determination and thought to make the most of what evidence we have. I hope this article has been a good reminder of seven areas where the mode of preparation and presentation can have a powerful and successful impact on your trials and on your community. ✤