I'm only familiar with Maryland and I know the laws vary state by state, but in Maryland the first step is the FST. If you fail the FST, the officer then requests a breathalyzer. If you pass the FST, they can still request a breathalyzer. However, you can refuse the breathalyzer at any point. If you do refuse, you will be charged with DUI if the officer smells any alcohol or if you admit to having even one drink. Normally, the refusal to take a breathalyzer is all but an admission of guilt. However, in Maryland you can go to court and if you can prove why you failed the FST (medical reasoning of course), there is a chance you could beat the charge. A lot of it has to come down to what the officer writes down in regards to whether or not you admitted drinking, your other actions, etc but it can be beaten although it rarely happens.
My Playoff Team - Please Comment
MSchaub, DMcNabb, JFreeman, KKolb
SJackson, THightower, CWells, JForsett, JSnelling, CJennings, QGanther
RWayne, RMoss, RMeachem, MCrabtree, DBowe