I'll just walk you through the entire process from the POV of a police officer:
- The traffic stop. When I approach and make contact, there are a lot of things that can raise my antennae when it comes to a possible DWI situation. This might be the smell of intoxicants, discarded containers, your speech cadence, your coordination in fine motor skills (fishing out paperwork and your license), whether your eyes exhibit indicators of intoxication, and any number of other things.
- The exit request. If I feel I have reasonable suspicion to believe that you might be intoxicated, once I run your information I'm going to reapproach and ask you to exit the vehicle. I can't speak to every jurisdiction, but in Missouri you cannot refuse this request – doing so will be Failure to Comply with Lawful Direction of a Law Enforcement Officer (or an equivalent), and will make the situation very ugly very quickly. As you exit, I'm again looking for indications of intoxication: difficulty manipulating door mechanisms, coordination in exiting, walking to the rear of the vehicle, and so on.
- The SFST request. At this point I'll simply tell you that I have reason to suspect intoxication and ask you to perform Standardized Field Sobriety Tests (SFSTs). Unlike the request to exit, you can legally refuse to perform these tests, which in Missouri consist of analysis of eye movement, a walk and turn test and a one leg stand. I might also ask you to perform non-standardized tests (counting off on your fingers, saying the alphabet without singing it, counting between odd numbers [for instance, from 87 to 98]. Nobody I worked with ever used the reverse alphabet test – for one, most habitual drunks had it memorized, and besides that, we all knew that we'd have trouble doing it ourselves, even sober and not hampered by the stress of a traffic stop. In my experience, there is only one reason anyone ever refused to perform them, and it wasn't because they were principled in the area of personal liberties. Not that that's an invalid reason, but if you were to do so, that will not be the officer's interpretation.
- The arrest decision. At the conclusion of testing (or after your refusal), I must determine whether I have probable cause to arrest you for DWI. I don't need you to perform SFSTs to get this – I arrested multiple DWI suspects based only on the above observations. With PC, I'll arrest; without, I'll usually release. If I lack solid PC but am uncomfortable with your driving, I may request you find alternate transportation.
- The post-arrest investigation. Once at the jail (in my case – could be station, precinct, etc.), I would read you Missouri Implied Consent (for the uninitiated, in Missouri your acceptance of a driver's license implies your consent to submit to a test of your blood or breath after being arrested for suspicion of DWI). It's been a while, but I think it read:
"You are under arrest, and I have reason to believe you were driving a motor vehicle while under the influence of drugs or alcohol. In order to determine the level of alcohol present in your blood, I am requesting you submit to a chemical test of your [breath/blood]. If you refuse this test, your driver's license will be immediately revoked for one year. Evidence of your refusal to take this test may be used against you in a court of law. Having been informed of the reason for my requesting the test, will you take the test?"
- The opportunity for chemical test. Here you have three immediate options:
- Accept. You will wait fifteen minutes to rid your mouth of any residual alcohol and then provide a breath sample.
- Decline. No testing occurs, but your license is revoked upon refusal.
- Request an attorney. You will be given twenty minutes to attempt contact with an attorney and will be provided with a phone. Important note: If you establish contact with an attorney, your conversation falls under attorney-client privilege, and I am precluded from documenting anything you say during the conversation. However, if you contact anybody else, everything you say is fair game for the report. I once absolutely hung a guy when he called his passenger and repeatedly demanded he lie in court about who was driving. After your attorney consult, you must then accept or decline.
- Completion of investigation. If you submit a breath sample and are under the legal limit, you'll either be booked on other charges or essentially 'unarrested' (in dozens of DWI arrests, I never had to do this). If you're over, you'll be processed for DWI. If you refuse, you'll still be booked in for DWI and given a court date. If you're booked for DWI, you'll have a mandatory five hour hold before you're released.
As others have noted, the easiest way to avoid this pony show is to not drink and drive. I wish anybody with the inclination had to see the carnage I've seen, which I'll spare my fellow Quorans even the description of. I'll be haunted with some of those images forever – and I wasn't even directly impacted. If you've got money for booze, you've got money for a cab. And if not, I will personally PayPal your fare.