Thank you for your corrections. I meant "reasonable suspicion" of course for the initial stop. I am surprised that this has been challenged successfully in multiple cases. If you don't mind sharing, can you give an example from your experience?
Thanks.
(This is out of curiosity; I do not have a DUI pending.)
Take, for instance, when the stop was based upon something that might not have been an articulated traffic violation. Air fresheners dangling from the rearview mirror is one example that has caused a few to be lost (and there is case law on one concerning drugs that spelled out that the dangling object has to be an obstruction to the driver's view). If the elements of the suspected violation are not properly established, then the stop can be tossed.
If the contact was ostensibly a consensual contact, but involved an officer calling someone over to them and then demanding ID can be an oops.
If the driver was determined to have made a lawful movement or the officer admitted to not quite seeing the suspected violation but believed it occurred, this can also cause the violation to get tossed.
Such events are uncommon from what I know, but they are a lot easier than fighting the chemical test. from what I have been told and witnessed, the next most vulnerable place is the probable cause for the arrest. If the FSTs are poorly conducted, or the results are arguably ambiguous, the probable cause for the arrest might be vulnerable to challenge. If the officer relied too heavily on the PAS (in the field) then he might have a problem since that test can only be used to detect the presence of alcohol, and not to establish a particular BAC. An officer that is about to shrug it off but only makes the arrest based upon a .08 or higher reading on the PAS might have some problems.
A good DUI attorney reviews the report and can often determine how likely he might be to prevail based upon the officer's articulation in the report. An articulate report can go a long way to encourage a plea deal. I have never lost a DUI case, and only one traffic case (my first - I cited the wrong section), but I also tend to write rather complete reports.