Assuming that you now have the police report, you will see for the first time the evidence against you. This is the evidence you will have to overcome to win at trial.
The report will typically contain a checklist for the field sobriety test, a printout of the PAS test, a printout of the breath machine result or (attached to the police report) a lab report showing the blood or urine test result (if you took one of these tests), and a narrative report of at least one of the arresting officers. If there were two officers, sometimes both will provide a narrative if they were responsible for different part of the process. For instance, one may give the narrative for why you were stopped and how you acted when asked for your license and registration, and the other officer may describe the field sobriety test, the PAS test, and the required test.
If you are like most folks who see a police report for the first time you will be shocked. Every statement made by the police will seem like a lie. For instance the report will likely say that your speech was slurred, your eyes were glazed and red, your clothing was disheveled, you had alcohol on your breath, you fumbled the license and registration, you staggered when you got out of the car, you couldn't stand on one leg without falling and you failed the heel-to-toe walking test. It will also likely tell you that you flunked the horizontal gaze nystagmus test (described above). Defense attorneys will tell you that these observations are so routine that the police are starting to dial it back a bit so they don't appear foolish in front of the jury.
Whether or not you agree with all, some, or none of what's in the report, it shows you in stark terms how the officers will be testifying if you go to trial. The reason you can depend on that is that a testifying officer will use the report to "refresh his or her recollection," which means in effect that the officer doesn't have to remember anything to testify against you. It also means that the officers won't stray from the report for a very good reason: If their testimony is substantially different than the report, you (or your attorney) could use the report to discredit an officer's entire testimony, and probably win the case. So, in virtually all cases, you can depend on the police report being the spine of the prosecution's case at trial. Read more about how field sobriety tests are used in DUI cases.
Once you see the prosecution's case, you'll need to address several basic questions:
If you chose a blood test and it put you at .08% or more, you have problems. There isn't much wiggle room for a blood test, although a good attorney can mount some kind of challenge to anything. (For example, read about the "rising-blood-alcohol defense.") It's possible that you could luck into some circumstance that might work in your favor—like happened in San Francisco in 2010 when a scandal involving a lab worker (with a drug habit) cast grave doubt on the crime lab's reports—but don't count on it. When the blood test is taken they will usually save a sample for you to have tested by an independent laboratory. Occasionally this independent sample will vary significantly from the original, but not very often.
If you chose a breath test (the required test, not the PAS) and the result is .11% or more, you'll also be hard-pressed to win. However, the breath test is somewhat less reliable than the blood test and there are more requirements regarding its administration, so you may be able to claim the test was mishandled.
For instance, they aren't supposed to administer the breath test until they have observed you for at least 20 minutes (under National Highway Traffic Safety Administration guidelines). This is to prevent any condition that would elevate the alcohol in your mouth (like belching). If they didn't wait the 20 minutes and you can prove it, you can effectively challenge the test results and possibly escape conviction under the .08% law. But remember, the officers will likely testify that you were under observation the whole time for at least 20 minutes (even if it's not specified in the report) and it will be up to you to prove them wrong, a hard sell to most juries.
In days past, the breath testing machines used under the implied consent rules preserved a sample of your breath for independent testing. However, the new portable machines usually don't preserve this additional sample. This is another reason why you should request the more accurate blood test if you are sure (and in a condition to be sure) that you are not over the limit.
Depending on your state, there may be issues dealing with when you drank and whether the test taken by the law enforcement officers accurately reflected your BAC during the time you were driving. For instance, if you drank a lot just before you got in the car to drive and then were tested well after the time you stopped driving, your BAC when tested may be considerably higher than when you were driving (because of the time it takes for the body to absorb the alcohol). And finally, some states still allow the defense to argue to the jury that people differ in how much alcohol they have in their blood for any given level of breath test, and these variations can cast reasonable doubt on the test as a whole.
All breath testing machines used under implied consent rules need to be calibrated at regular intervals recommended by the manufacturer. Failure to maintain accurate calibration records can undermine the evidentiary effectiveness of a test result. The calibrations typically are based on samples provided by outside agencies or private companies. If these samples are wrong, then the test is wrong. If the original provider of the calibration sample does not appear at your DUI trial (which is often the case with the newer model machines that rely on calibration samples produced by private enterprise), the calibrator's testimony will be based on the provider's out-of-court representation regarding the strength of the sample. This out-of-court representation is hearsay and arguably not admissible on that ground. This means that the calibrator can't explain why his calibration is accurate (without using the prohibited hearsay), and without that testimony the admissibility of the actual test given to you can be challenged. Simply, the alcohol test method of DUI prosecution, which is ultimately based on the accuracy of a sample produced by private enterprise, may be built on a hearsay house of cards that may come tumbling down sometime in the future.
But not so fast. This attack on calibration sample hearsay evidence was raised in one jury trial in Northern California. When the defense attorney objected to the admission of the calibration testimony on hearsay grounds, the judge opined that it was a "very clever" argument but that if he ruled in the lawyer's favor on this argument the word would spread and there would never be another conviction under the state's .08% statute. What could the lawyer say to that judicial reasoning? In the midst of its deliberations the jury asked the judge whether anyone had ever raised this particular point before in a court? The judge didn't know and refused to answer the question. The jury went on to convict the defendant on the .08% charge. (The jury hung on the issue of "under the influence" which had no practical effect on the defendant.)
Not many states continue to use urine tests, because of the three tests (blood, breath, and urine), the urine test is probably the least accurate. This is because the percent of alcohol in the urine is not necessarily the same as in a person's blood. The level of alcohol in urine is about 1.33 times the BAC level. So, to convert a urine test result into an equivalent blood alcohol level, divide the urine alcohol level by 1.33. However, this number is an average, and you can argue at trial that this average figure didn't apply to you. Also, a sample will normally be preserved so you can arrange for an independent test. If you're in the unfortunate position of knowing you had way too much to drink and are offered a choice, the urine test is the one to pick.
The National Highway Traffic Safety Administration has established guidelines that all law enforcement officers must observe when conducting field sobriety tests. In past years, there were a large number of these tests, but most were easily subject to challenge in court due to their inherent unreliability. Now the NHTSA recommends only three. Your state's regulations may depart in the requirements for giving these tests, but any significant departure would be a point to argue to the jury to blunt the force of any negative observations during the test.
A victory on the "under the influence" charge won't help you with the .08% charge. Many people who think about fighting their DUI concentrate on the difference of opinion between themselves and the arresting officers in terms of their demeanor, their driving, the reason they were stopped, their performance on the field sobriety tests, and what they may have said to the officers in the course of the process. And this is understandable. Nobody likes to be falsely accused. Unfortunately, none of that matters if the test shows that you had more than .08% blood alcohol content and the jury believes it (which they almost always do). Even if the jury believes you on all the other points, and acquits you of the driving under the influence charge, a conviction on the .08% charge—called a "per se" DUI—will have the same effect as if you were convicted on the other.
Your DUI case may be different in some important aspect from a typical case and that could work in your favor. If any of these circumstances apply to you, you may have an improved chance of success at trial: