KEVIN FAYLE, FindLaw.com

While driving home after a night out with friends, you see the flash of red and blue lights in your rearview mirror, instructing you to pull over to the side of the road. If you have been drinking, it is important to know your rights and options should the officer choose to investigate you for driving under the influence. And, if you have made the unfortunate decision to drive while impaired, you should also know what to expect during your arrest and subsequent booking.

First of all, what exactly does it mean to be "driving under the influence"? While the name and the exact elements of the offense vary from state to state, it is essentially illegal to operate a motor vehicle if:

1) The driver's ability to safely operate the vehicle is impaired by the effects of drugs or alcohol, or

2) The driver is intoxicated at a level above established DUI standards, such as blood-alcohol concentration (BAC).

Driving while intoxicated past the point of DUI standards is known as "per se" DUI. A person does not necessarily have to pass the established DUI standards in order to be arrested and charged with DUI, however; even at a legal level, police can arrest drivers if their driving abilities are impaired as a result of the consumption of drugs or alcohol. Moreover, some states have zero-tolerance policies for certain classes of drivers, such as minors. In these states, even the slightest trace of impairment can lead to a DUI arrest and prosecution.

The police can stop motorists on suspicion of violating traffic laws, but an officer needs probable cause to arrest a driver for DUI. DUI offenses are criminal, and can even involve felony charges if someone other than the driver was injured.

Typically, police officers establish probable cause using three methods: 1) observation; 2) sobriety tests; and 3) chemical tests. The Supreme Court has held that a driver's Miranda right to remain silent does not come into effect until after the officer has placed the driver under arrest. Thus, an officer does not have to read a driver their rights before asking questions related to their drinking and/or drug consumption, or before conducting field sobriety tests.

A driver may refuse an officer's request that they take a chemical test - such as a breathalyzer analysis or blood test - and some states even afford a driver the opportunity to consult an attorney prior to making the decision. If a driver chooses to decline, however, most states have "implied consent" laws on the books that can result in the suspension of the driver's license - even if they are eventually acquitted of the drunk driving charge.

The Supreme Court has also upheld traffic checkpoints with the purpose of screening for drunk drivers, so 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 the drivers generally. It is legal for officers to stop a person's car and ask routine questions, but if the officers wish to detain the driver for more detailed questioning, a higher level of individualized suspicion is required.

If an officer decides to arrest a driver after determining that they have operated their vehicle while intoxicated, they must read them their rights. If they do not, any statements made by the driver past that point will not come into evidence at trial. This does not mean that a court will not find the driver guilty of driving while intoxicated, but it will reduce the amount of evidence available to prosecutors.

After an arrest, an officer will "book" or "process" the driver. This will involve some time spent in jail, after which the option of bail is usually available. Sometimes, however, bail will be set later by a judge at the arraignment. As a condition of release on bail, the driver promises to appear in court for all scheduled criminal proceedings.

If a driver cannot afford to pay the full bail amount, they may post a bond that guarantees that the full bail amount will be paid if the suspect fails to appear as promised.

In some cases, drivers may be granted "own recognizance release," which does not require any bail money or the posting of a bond. The driver must promise to appear at all criminal proceedings, however, and if they fail to do so, they are subject to immediate arrest, with very little possibility of obtaining bail in the future.

Check back for more of FindLaw's continuing series on DUI/DWI issues. The next installment will examine issues and choices that face defendants during DUI/DWI trials.