There are a variety of errors in a DUI traffic stop that could lead to a case dismissal if they are proven to the court. The constitution protects us from being arrested and charged without probable cause. This is why the police ask you to perform field sobriety tests – they need to establish probable cause for an arrest.
The law does not require individuals stopped by police to agree to perform field sobriety tests. To establish probable cause, there are a variety of types of evidence of intoxication that the law enforcement officer could claim. These include weaving while driving, but this can be exaggerated to the claim that you were "weaving within your lane". If you are not violating the law, this could be a questionable reason to pull you over.
Another issue that comes up is how the field sobriety tests are administered. With the most carefully administered tests, the most accurate of all the tests – the horizontal gaze nystagmus – is only 77% accurate, according to the NHTSA. The walk and turn test must be administered on a flat surface. There are many issues with these tests that could be challenged if they were administered incorrectly, as they often are. A breathalyzer test done at the roadside is much more likely to be faulty with regard to the BAC level. The administration of these tests should be reviewed for errors, as this could be helpful to your case.
At roadside checkpoints, any racial profiling is illegal. If it can be shown that you were selected to be pulled over based upon any form of profiling, this is a rights violation.
Don't go to court without a San Jose DUI lawyer to assist you. It may be possible to have your charges dismissed.