The police through training and experience will try to use a list of buzzwords in their report to justify your arrest. They love to say things like: strong odor of alcohol, slow to pull over, driving outside the lane lines, bloodshot watery eyes, slurred speech, poor performance on field sobriety tests, confused, etc.
Every one of these things can be explained. A crafty trial lawyer will be able to get the officer to admit that things other than alcohol or drugs can cause the very things the officer is relying on to justify his arrest. He will have to admit these things because they make common sense or are in the manual.

For instance, an odor of alcohol even a strong one is not an indication of impairment. It is only an indication of consumption. Taking 20 seconds to pull over can be explained depending on the area. Are there any other cars around? Is the driver familiar with the area? Is there a lack of safe places to pull over?
Marked lanes violations or driving over the lines can also be explained. Often drivers will do this all day long. We have all seen people do this on a daily basis and the first thing in our mind is not always that the person must be drunk. People fiddle with the radio, cell phones, cigarettes, sometimes a bug will fly in the car. Some people will even drive like this normally to straighten out the road.

Red and watery eyes can be caused by wind, allergies, crying, irradiation from smoke, etc. Some people wear contacts or have dry eyes. All these are normal things that have nothing at all to do with drinking and driving.
Slurred and slow speech is not always a sign of impairment. Some people talk like this all the time. Some people are naturally hard to understand. Some clients are here on a visa from other countries working or going to school. English is not their primary language. The officer will usually never have heard the person talk before.
People with back, neck, leg, knee, balance, and other medical problems will have difficulty performing the tests. Officers are trained to take any claimed ailments into consideration, usually proceed with testing anyway. That is simply unreliable and most juries will understand that. If you are super lucky you will get someone on your jury that has balance problems or knows someone that is naturally uncoordinated that would never be able to pass these tests.
Mental confusion can be evidenced by unusual answers to questions, statements of traveling in the opposite direction from a stated destination, etc. It is natural to get lost without GPS at night in an unfamiliar area. That does not mean you are drunk. Every cop or juror will have to admit that they have been lost before or missed their exit or turn because they were thinking about something else and not paying attention when they had not consumed any alcohol at all. This does not mean a person is drunk.

I used these very same techniques to win a jury trial a few weeks ago. They jury came back about 30 minutes later with a verdict and said not guilty. They commented that they thought my client might have been under the influence, but that the state just didn’t prove it. This is not to say that all cases are winnable, but even with all the buzz words, remember that an experienced DUI lawyer can help generate a defense to the charges and have a chance to win!