Police typically use three methods of determining whether a driver has had too much to drink to be driving (intoxicated), or is under the influence of drugs:
You may refuse to take a chemical test (breathalyzer, blood test, or urine test) during a DUI or DWI stop, but almost every state has a so-called "implied consent" law that says a refusal can result in suspension of your driver's license from anywhere between three to 12 months. (This is true even if you're eventually found not guilty of the drunk driving/driving under the influence/driving while intoxicated charge.) Further, if your drunk driving case goes to trial, the prosecutor can tell the jury that you wouldn't take the test, which may lead the jury members to conclude that you refused because you were, in fact, intoxicated or under the influence of drugs.
The answer depends on where you live. In California, for example, you don't have the right to speak with an attorney first before you decide whether to take a breath, blood, or urine test. But some states, including Arizona, allow you to talk to your lawyer before you take a chemical test.
Sometimes. Whether a police officer has to read you your rights on a DUI or DWI stop depends on whether or not you are in police custody -- that is, whether you are subject to the restraints common to a formal arrest. The U.S. Supreme Court has ruled that the police do not have to provide Miranda warnings during roadside questioning of a motorist detained pursuant to a traffic stop. Thus, roadside questioning about your drinking, drug-taking, or performance on field sobriety tests does not constitute "custodial interrogation." However, once you are arrested -- or restrained by the police in a manner consistent with arrest -- you must be read your Miranda rights.
Defending against a charge of drunk driving is a tricky business. Defenders need to understand scientific and medical concepts, and must be able to question tough witnesses, including scientists and police officers. If you want to fight your drunk driving/driving under the influence/driving while intoxicated charge, you're well advised to hire an attorney who specializes in these types of cases.
These days it is hard to "win" a drunk driving case, assuming the police gathered some physical evidence against you (results of a breathalyzer, blood test, or urine test). And the punishments for DUI are pretty standard. If you were truly guilty, there's no guarantee that a lawyer could get you a better deal or plea bargain than you can get for yourself.
If the police don't have physical evidence against you (for example, you refused the chemical test), a good lawyer may be able to plea your case down to a "wet reckless" (alcohol-related reckless driving). However, while a wet reckless may not sound as bad as a DUI or DWI, it often carries almost the same fines and penalties as a DUI or DWI.
Yes, as long as the police use a neutral policy when stopping cars (such as stopping all cars or stopping every third car) and they minimize any inconvenience to you and the other drivers. The police can't single out your car at a roadblock unless they have good reason to believe that you've broken the law, such as by driving under the influence of alcohol or drugs (DUI) or driving while intoxicated (DWI).
For an extensively updated resource that reflects your state's current traffic laws and court procedures, get Beat Your TIcket: Go to Court & Win, by David Brown (Nolo).
It's illegal to drive a car while "impaired" by the effects of alcohol or drugs (including prescription drugs). This means that there must be enough alcohol or drugs in the driver's body to prevent him from thinking clearly or driving safely. Many people reach this level well before they'd be considered "drunk" or "stoned."
Additionally, an adult who has a blood alcohol content (BAC) level of .08% or above is guilty of a DUI (driving under the influence) or DWI (driving while intoxicated) -- no matter how sober the driver feels, or how well that person was driving.
However, almost all states consider drivers under the age of 21 to be driving under the influence of alcohol if their BAC is at or greater than .01% or .02%, depending on the state.