He was not smart after all. Of course the field sobriety tests can (and will be) used against you in court. 

The point of refusing the tests is to refuse ALL of them. Not some of them! This includes the very first test where the officer asks you to track his pen with your eyes (sometimes a small flashlight is used instead but it does not matter). It’s called the horizontal gaze nystagmus (“HGN”). The test is based on the fact that alcohol affects the automatic tracking mechanisms of the eyes. As a person’s blood alcohol concentration increases, the eyes will “jerk” sooner as they move to the side. The HGN test claims to gauge intoxication by measuring the involuntary oscillation of the eyes. 

So, if you are smart (in my opinion) you refuse the HGN test, then you refuse the field sobriety tests and then you refuse the breathalyzer test. Refuse them all. If not, you will end up like the “smart guy” who refused one test and gave in to the others. Dumb. Dumb. Dumb.