What Happens in a Traffic Ticket Jury Trial outlines the basic procedures in a jury trial for other types of traffic tickets. In a DUI trail, there are several additional points of interest.
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.
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.
If the police illegally arrested you or obtained any evidence against you in an illegal manner, you may be able to schedule a special pretrial hearing to suppress certain evidence. The prosecution is then prevented from using it at trial. For example, if you consented to give a blood sample only after the police beat you into submission, you may want to make a motion to suppress the test results which, if successful, would keep the test from being introduced into evidence at trial. A motion to suppress is heard several weeks (sometimes months) before the trial actually takes place. It is heard only before a judge, perhaps one who will not be presiding at your trial. This type of motion is fairly technical and complicated, and will probably involve cross-examining the officer who arrested you. Hire a lawyer to do this for you—do not to try to handle it yourself.
One common reason to pursue a motion to suppress would be if you believe that the officers had no probable cause to stop you and that the subsequent observations and tests should be kept out of evidence as "fruit of the poisonous tree." While this argument is legally tenable, it almost never pans out for one simple reason. To stop you, the officers only have to have probable cause that you violated any rule of the road, from driving with a broken taillight to not having your seatbelt on. They don't have to have any clue whatsoever that you were driving under the influence. Not surprisingly, it's a rare police report that doesn't contain some reason for stopping you.
A person who pleads guilty to or is convicted of a second or third offense of driving under the influence can suffer a far heavier penalty than a first offender. To obtain the heavier penalty, the prosecution must "charge" the prior conviction against you. When you initially plead "not guilty" to the offense, never admit any priors charged against you. Simply "deny" them. This is perfectly legal. If you "admit" them, you destroy any chance of challenging their validity on technical grounds. By having a prior conviction "stricken," you face a less-severe penalty if convicted on the current charge. The procedure to strike a prior is based on whether you were properly informed of or intelligently waived certain rights at any hearings related to the prior offenses. Again, this type of motion is extremely technical and will require a lawyer's help.
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.
Educate yourself, even if you hire a lawyer. There are a wide variety of other strategies and approaches to handling a DUI trial that can't reasonably be detailed in this type of book, but a good DUI defense treatise, such as the one by Laurence Taylor mentioned earlier, can provide lots of additional help. Please understand that we are not recommending you handle your own DUI trial. Even if you are represented by a lawyer, however, the more you read about DUI and possible defenses the more you'll have to bring to the table.