There have been some serious violations of the conceptual field sobriety testing parameters IMO.
Of note, there have been some agencies in TN which are in big trouble for arresting folks who blow a .000 on the PBT and little else in terms of evidence of intoxication.
Much more reliable is the NHSTA SFST (standardized field sobriety test) protocol. It is not fool-proof. It is reasonably accurate as a predictor of intoxication.
SFSTs are not an absolute reason for arrest; they are building blocks of reasonable suspicion working towards probable cause for arrest.
Here is the real information:
https://www.nhtsa.gov/dwi-detection-and-standardized-field-sobriety-test-sfst-resources
Here's the conceptual premise:
- there are three general tests; eye-gaze-nystagmus, one-leg stand, walk and turn
- three or more "clues" in a test indicate a test failure
- the more tests which are failed, the more likely you are intoxicated
Technically, (I know this is true in IN, and likely true in all states), you are not under arrest until you fail a certified breath test or blood test, or formally refuse those tests. You are only "being detained" during testing and when being transported.
Because driving is a privilege, those tests are considered to be under the "implied consent" doctrine. As soon as you operate a vehicle, you have given implied consent to testing by your choice to exercise the privilege.
In Indiana, refusal to take the tests results in an automatic suspension of your license for one year,
regardless of the outcome of any legal proceeding. This is because, again, the BMV has control over your "privilege". Driving is not a "right" and therefore falls outside of normal claims of duty and response.
Each state will have nuances which vary slightly from this, but the general concept applies to all as best I understand.
For reference, I was NHSTA certified in SFSTs for most of my career. It's not a requirement to be so, but it certainly helps when it comes time to testify in court.