If defendant's interpretation of Dyer's testimony is correct, all evidence derived from those tests would be inadmissible. Consequently, an officer must have either a search warrant to conduct the tests or the authority to conduct them must come within one of the recognized exceptions to the warrant requirement. One exception to the warrant requirement is a search conducted with probable cause and under exigent circumstances. That is the exception on which the state relies to uphold the tests in this case. Under that exception, an officer must have probable cause to believe that a person is driving under the influence of intoxicants before administering field sobriety tests to that person.
Probable cause has both an objective and a subjective component.
An officer must subjectively believe that a crime has been committed and thus that a person or thing is subject to seizure, and this belief must be objectively reasonable in the circumstances. Defendant does not contend that Dyer lacked an objective basis to believe that defendant had driven while under the influence of intoxicants before Dyer administered the field sobriety tests. His challenge, rather, implicates the subjective component of probable cause. At the suppression hearing, when Dyer was presented with the statutory definition of probable cause and asked when he had developed his belief that he had probable cause to arrest defendant for DUII, he stated that he did so after administering the field sobriety tests. That statement, and the sequence it describes, is entirely consistent with the regime that governed DUII stops before Nagel .