If you are pulled over by a police officer and they suspect you of driving under the influence, then you will most likely be asked to perform the standardized field sobriety tests (SFST). There are at least a dozen variations of these tests but the standard three are: horizontal gaze nystagmus (i.e. follow my finger test), single leg stand, and heel-to-toe walk and turn.
If you take these SFSTs you will most likely fail. The scoring of the test is left entirely up to the investigating officer and chances are if he has asked you to perform the SFSTs then he has already decided to arrest you. By performing the SFSTs you are only giving the police officer, and ultimately the prosecutor, more evidence to use against you at trial.
The SFSTs are voluntary and refusing them will not result in loss of your drivers’ license. This is different than refusal of a breath or blood test which does result in the loss of your drivers’ license. If you have a medical condition which would prevent you from doing the tests make sure to to tell the police officer at the time he asks you to take the SFSTs. Raising that issue later on is not as believable and looks like you are trying to excuse your actions. Your refusal to take part in the SFSTs will be used against you at trial, but your DUI defense attorney can help explain the refusal to the jury. This is generally better for your case than having the prosecutor tell the jury how poorly you did on the SFSTs.