Using Witnesses in Your DUI Trial

If you go to trial to fight your DUI, you and your lawyer will probably try to use witness testimony to bolster your case.  The two most helpful types of witnesses are expert witnesses, who testify about the technical aspects of the evidence, and observer witnesses who testify about what actually happened when you got your DUI. You may also be tempted to be a witness for yourself.

Expert Witnesses

Almost all DUI trials involve scientific measurements that require the prosecution to use an expert witness. An expert witness is somebody who has expertise in a particular subject that is not usually shared by the general public. In the case of a DUI prosecution, law enforcement officers tasked with enforcing DUI laws usually have received training in a variety of areas and can qualify as experts in those areas. However, there are few if any law enforcement officers who are qualified to testify about how the machines arrive at a .08 blood alcohol content and the effect (scientifically speaking) that alcohol at any level can have on your physical and mental faculties. If the trial involves marijuana, methamphetamine, or other drugs, the need for an expert witness is even greater. Of course this is the prosecution’s burden, but if you hope to cast any substantial doubt on what one of these expert witnesses has to say, you’ll have to have your own expert. While it’s tempting to get your own evidence in through clever cross-examination, even highly skilled and experienced attorneys bring their own expert rather than relying on cross-examination to establish their defense.

Expert witnesses don’t come cheap (figure a minimum of $1,000), so right away, if you want to win a DUI trial involving a .08 measurement, or the presence of alcohol or drugs in a blood sample, you’ll need to shell out a fair amount of money. Some states allow indigent people (whether they are representing themselves or are represented by a private attorney) to apply to the judge for permission to hire an expert at the state’s expense, but be prepared for a hard sell, especially if the judge has little or no reason to think you can win your case.

Observer Witnesses

At trial, regular witnesses who testify to one or more aspects of your defense are only helpful if they can convince a jury about facts that they directly observed and that would be helpful to your case. Opinions are not relevant (unless your witness also quali­fied as an expert in a particular area). Close relatives such as a wife, brother, or son and daughter may be as trustworthy as the day is long, but a jury is unlikely to give much credence to their testimony. The same is true for friends and co-workers. For witnesses to be credible, they must have little or no ties to you, yet be willing to testify on your behalf on the basis of their observations. These are hard to find in a DUI case. In reality, the defense in most DUI cases is limited to cross-examination of the prosecution’s witnesses and direct testimony by the defense expert witness, who is usually a toxicologist who (at a steep cost of $1000 or more) can sometimes discredit the blood, breath, or urine test or bolster one or more other elements of the defense.

You as a Witness

In most cases you will be the only possible witness to contradict the police version of events. You have a constitutional right to take the stand but also a constitutional right to not take the stand. When making this decision, the core question is, will the jury believe you? All they have to do is disbelieve one thing you say and you can usually kiss the rest of your testimony goodbye. If you have a criminal history, the prosecutor may be able to use it as a way to “impeach” your testimony in this case (especially if it’s a felony). If your version of events contradicts that of two or more police officers, guess whom the jury will believe? If the police say that you misstated the amount you had drank when they first questioned you, the prosecution will hammer away at this as a lie. If you are prone to excitability or anger when questioned closely, pretty much any prosecutor will rattle you to the great detriment of your case. Yes, you have a right to take the stand, but it will be a daunting test of your composure and expressive skills, as well as a test of the viability of your story.

Excerpted and adapted from Beat Your Ticket: Go to Court & Win, by David W. Brown (Nolo).