There are several circumstances which would provide a police officer the reasonable suspicion to come into contact with a suspected drunk driver. The most common reason is the observation of erratic or suspicious driving—such as swerving, driving the wrong way, speeding or driving too slowly, or driving with the lights off, for example. An officer can also stop a vehicle for a lesser traffic offense and then notice signs of intoxication warranting starting an investigation. Other circumstances which may warrant a police officer stopping a motorist include a traffic accident or responding to a report by another person that a motorist is driving erratically.
Investigation phases
The NHTSA put forth three specific phases police officers should use when conducting a DWI investigation. Phase 1 is the “vehicle in motion,” Phase 2 involves “personal contact” with the motorist, and Phase 3 is the “pre-arrest screening.”
More specifically, Phase 1 addresses the officer’s observations of the suspect’s driving. Phase 2 begins when the officer actually stops the motorist. If the officer notices any symptoms indicative of the subject being under the influence such as an odor of alcohol, slurred speech, red or bloodshot eyes, droopy eyelids, confusion, poor fine motor skills, for example, s/he likely has reasonable suspicion to make contact with the driver. Finally, Phase 3 occurs when the officer administers standardized field sobriety tests (SFSTs) and questions the subject. Phase 3 also encompasses the administration of any post-arrest chemical tests.
Field sobriety tests
As mentioned, during Phase 3, officers administer SFSTs. The NHTSA has published many training manuals on how to best conduct these tests, their accuracy, and those people for whom certain tests are not recommended. For example, the walk-and-turn test and one-leg stand test are 65-68 percent accurate for most suspected drunk drivers; however, said tests are not validated for those with medical conditions or injuries, who are morbidly obese, or who are 65 years of age or older. Along with the horizontal gaze nystagmus test, these three tests are, largely, validated by the NHTSA.
There are other field sobriety tests officers may use to determine if someone is under the influence. These include the finger-to-nose test, finger count test, counting backward, reciting the alphabet, the Romberg balance test, and administering a preliminary alcohol screening (PAS) test or preliminary breath test (PBT) which involves having the suspect breathe into a small, handheld breathalyzer device.
While you may refuse to participate in SFSTs—except for the preliminary breath test which could result in additional charges for violating the state’s implied consent law—said refusal just increases the officer’s probable cause to arrest you.
