But would their sobriety test hold up in court or what happens when you fail their field test (but pass the other test). If it doesn't hold up in court (because the scientific tests confirmed sobriety), why would they even bother doing both tests? As far as I know, breathalyzer are far more accurate (less false negatives and positives). This makes me wonder why they would even consider doing the other test. They could catch actual drunk drivers with the time saved and have less work to do (because they don't need to file out paper work for sober drivers).

As far as holding up in court, I'm not sure. But most cases never go to trial, and a plea agreement is simply made.