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DWI investigations: Testimony preparation, attitude help ensure courtroom success

Focusing on impaired driving apprehension is critical for safer roadways


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

For the majority of cops, testifying in court on any investigation and even more so with DWI investigations, can be daunting. However, testifying in court is a great way to enhance your knowledge of the field and boost your confidence all around.


Before your case goes to trial, meet with the prosecutor and get adequately prepared. Discuss any issues or concerns you have with the case and strategize on how best to tackle them. Go over the questions to be asked on direct examination. Make preparations for potential defense arguments and create a plan to counter them.

A good prosecutor will be willing to spend time preparing you for trial because your testimony is the most vital piece of the puzzle. An ounce of preparation is worth a pound of cure.

Included in that preparation are studying your case, relevant case law and the National Highway Traffic Safety Administration manual. You need to be prepared to answer any questions and be knowledgeable and confident in your answers or the jury will not give your testimony much weight. If that happens, your case is lost.

DWI investigations take a lot of work so why jump through all the hoops just to blow the case at trial? Go into the trial knowing the accuracy of standardized field sobriety tests (SFSTs) and the studies that validated them because the defense may question you about this.

I once had a defense attorney challenge me to name three additional countries that use SFSTs. Luckily, I had prepared ahead of time but had I not, I would have had an uphill battle from that moment on.


When you show up for trial, be “dressed to the nines.” Though a police uniform is far less comfortable than a suit, jurors like to see a sharp-dressed, polished and decorated officer in uniform. If you have medals, awards or citations, wear them on your uniform. I have a separate duty belt, boots and regalia that I keep just for court.

Once you take the stand, smile and acknowledge the jurors. Avoid leaning back in the chair or taking a defensive posture. Instead, lean forward and be openly engaged in the proceedings.

When the prosecutor asks you to qualify yourself at the beginning of direct examination, seize the opportunity to share information about your education, training, experience, certifications, awards and accomplishments. Typically, cops will downplay these things to remain humble; however, this is the only chance you have to tell the jury why they should listen to you and value your testimony.


If you are asked a question to which you do not know the answer, do not be afraid to simply say, “I don’t know.” There is no need to sugarcoat that answer or dance around it, nor does saying it make you incompetent. The only time you should worry is if that becomes a repetitive answer for you. Also, be cautious not to bite off more than you can chew or testify on matters of which you are not qualified to speak. Know your limitations.

Avoid being too quick to provide an answer – give your prosecutor time to object. Do not become inappropriately argumentative with defense counsel. This is a surefire way to sink yourself in the eyes of the jury. Remain calm, cool and collected, and allow defense counsel to be theatric without getting a negative response from you.

During direct examination, after the prosecutor asks you a question, physically turn and answer that question directly to the jury. Do not be monotone, robotic or procedural about it either. Show some personality and engage the jury as they will reciprocate.


Throughout this series, I have discussed several methods that may benefit you and enhance your ability to investigate DWI offenses.

These approaches are an amalgamation of nearly a decade of experience and specialized training directly relevant to the subject matter. For someone aspiring to become a better DWI officer, I hope these articles provide a solid foundation to build on.

Intoxicated drivers remain a serious concern for law enforcement and the public. As a profession, we need to concentrate more seriously on prevention and apprehension, and it starts with rank-and-file officers.

I will leave you with an alarming fact about my home state. In Texas, every day since November 7, 2000, our roadways have experienced at least one fatal crash. You read that correctly – 21 years straight. Let’s get out of the problem and into the solution, together. #EndTheStreak

Police1 resources on effective courtroom testimony

Deputy James “Zack” Holley is a patrolman for a southeastern sheriff’s office in Texas. Along with a bachelor’s degree in criminal justice from Sam Houston State University, Deputy Holley holds a Master Peace Officer’s license, is a certified Drug Recognition Expert, an SFST instructor, a vehicle crash expert/reconstructionist, field training officer and firearms instructor, and has received several awards throughout his career. Deputy Holley has several hundred DWI arrests and thousands of enforcement hours under his belt.

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