Despite police and prosecutor claims to the contrary, field tests are an unreliable indicator of sobriety and are primarily used to gather evidence for use against suspects.
Hopefully, you limited the accumulation of adverse evidence, beginning with being respectful and responsive when the officer pulled you over. If you were argumentative or uncooperative, the prosecutor and jury are likely to think it was the alcohol talking rather than an unimpaired driver. Most people do not know that they have an absolute right to refuse to perform any field sobriety tests - and the fact that you refused cannot be used against you.
These so-called "tests" are nothing but coordination exercises that may not prove anything at all about sobriety. Indeed, the trial judge should be asked to prevent the police or prosecutor from using the word "test" in describing what you were told to do.
Some of the "tests", such as the horizontal gaze nystagmus and the portable breathalyzer results, cannot be used at trial in Massachusetts.
The primary problem with field tests is the officer's failure to establish a baseline. In other words, the officer does not know how you perform on these tests when no alcohol is involved. As you would expect, sober individuals vary widely in their ability to perform balance and dexterity tests.
There are a number of excellent strategies for weakening the officer's testimony about your performance on the field sobriety tests, as well as his or her claims that your eyes were glassy and bloodshot, you were unsteady on your feet and there was an odor of alcohol from you or the car.