DWI is an acronym for driving while intoxicated. A similar acronym, DUI, is used in other states which stands for driving under the influence, and yet another acronym, DWAI, may be encountered which signifies driving while ability impaired.
Under section 1192 of the New York State Vehicle and Traffic Law (VTL), the prohibitions against a motorist's consumption of alcohol or drugs include:

• Driving while ability impaired: "No person shall operate a motor vehicle while the person's ability to operate such motor vehicle is impaired by the consumption of alcohol" (VTL §1192[1]). A first violation is a traffic infraction.
• Driving while intoxicated; per se: "No person shall operate a motor vehicle while such person has .08 of one per centum or more by weight of alcohol in the person's blood as shown by chemical analysis of such person's blood, breath, urine or saliva . . . " (VTL §1192[2]). A first violation is a misdemeanor.
• Driving while intoxicated: "No person shall operate a motor vehicle while in an intoxicated condition." (VTL §1192[3]). A first violation is a misdemeanor.
• Driving while ability impaired by drugs: "No person shall operate a motor vehicle while the person's ability to operate such a motor vehicle is impaired by the use of a drug . . ." (VTL §1192[4]). A first violation is a misdemeanor.
• Driving while ability impaired by the combined influence of drugs or of alcohol and any drug or drugs: "No person shall operate a motor vehicle while the person's ability to operate such motor vehicle is impaired by the combined influence of drugs or of alcohol and any drug or drugs" (VTL §1192[4-a]). A first violation is a misdemeanor.
• Aggravated driving while intoxicated; per se: "No person shall operate a motor vehicle while such person has .18 of one per centum or more by weight of alcohol in the person's blood as shown by chemical analysis of such person's blood, breath, urine or saliva . . . " (VTL §1192[2-a][a]). A first violation is a misdemeanor.
• Aggravated driving while intoxicated; with a child: "No person shall operate a motor vehicle while [intoxicated, impaired by drugs, or impaired by the combined influence of drugs or of alcohol and any drug or drugs] while a child who is fifteen years of age or less is a passenger in such motor vehicle" (VTL §1192[2-a] [b]). A first violation is a class E felony.
• Other provisions of VTL §1192 prohibit the operation of certain commercial vehicles at BAC levels lower than those specified in VTL §1192.

All alleged violations of §1192 of the VTL are prosecuted as criminal offenses and conviction subjects the motorist to specified penalties that vary according to: (1) the seriousness of the particular offense, which ranges from a traffic infraction to a class D felony, and (2) the motorist's record of certain prior driving-related convictions. Upon conviction, the court may impose a fine (the lowest amount for the least serious offense is presently $500.00) and/or a period of imprisonment (the longest period for the most serious DWI offense is presently an indeterminate sentence of imprisonment with a maximum term of seven years at a State correctional facility) (VTL §1192[3]). Penalties increase for repeat convictions within certain time periods.

In addition to the imposition of a fine and/or period of imprisonment, the court must also sentence a person convicted of driving while intoxicated or aggravated driving while intoxicated to a period of probation or conditional discharge and, as a condition of which, order such person to install and maintain an ignition interlock device in any motor vehicle owned or operated by such person during the term of such probation or conditional discharge. An ignition interlock device connects to a motor vehicle's ignition system and measures the alcohol content of the operator's breath. It prevents the vehicle from being started until the motorist provides an appropriate sample breath.

In addition to the imposition of a fine and/or period of imprisonment, a conviction for driving while intoxicated, aggravated driving while intoxicated, or driving while ability impaired by drugs requires the motorist to pay a driver responsibility assessment of $250 per year for the next three years (VTL §1199).

In addition, a violation of any provision of §1192 of the VTL or a refusal to submit to a properly requested chemical test automatically initiates separate administrative proceedings before the New York State Department of Motor Vehicles where determinations of a violation or a refusal result in a mandatory suspension or revocation of a motorist's driving privileges for stated periods of time.

Lastly, apart from these court and administrative proceedings, a motorist's record of DWI or DWAI may also trigger substantially higher automotive insurance premiums.

Under circumstances set out in VTL §1194, a police officer is authorized to request a motorist to submit to a chemical test and the law provides that "[a]ny person who operates a motor vehicle in this state shall be deemed to have given consent to a chemical test of one or more of the following: breath, blood, urine, or saliva, for the purpose of determining the alcoholic and/or drug content of the blood . . . ." When an authorized request is made, a motorist is then said to have given his or her "implied consent" to submit to the chemical test. A refusal to submit to a test after a proper request carries mandatory administrative consequences involving the loss of driving privileges and a civil fine (regardless of the outcome of any related DWI or DWAI charges in court) and in the event of such a refusal the police officer or district attorney may apply to a court asking it for an order to compel the motorist to submit to a chemical test.

"BAC" is an acronym for Blood Alcohol Content; the amount of alcohol in a person's body measured by the weight of the alcohol in a certain amount of blood. Breath analysis is the primary method used by law enforcement agencies to determine BAC, although a direct analysis of blood for this purpose is not uncommon. The first practical breath analysis device was designed in the 1930s by Dr. Rolla Harger of the Indiana University School of Medicine and was known as the Harger Drunkometer. This device was widely used for many years until the Breathalyzer, which was designed by Dr. Robert Borkenstein in 1954, replaced it. The Breathalyzer uses the relationship between a person's alveolar (deep lung) air and blood. This system collects a fixed volume of alveolar air and passes it through an alcohol-sensitive chemical reagent. Alcohol in the sample produces a color change in the reagent which is measured by a photometric system and yields a resulting BAC. While the Breathalyzer has been and continues to provide an accurate BAC, technology advancements have produced new and improved methods of analyzing breath to determine BAC. All of the newer evidential breath analysis devices employ infrared technology to measure alcohol in the person's blood by calculating the amount of infrared energy absorbed by the alcohol contained in the person's breath sample. These newer instruments are microprocessor-based, enabling faster and easier operation, as well as having the ability to record and print breath test results.

The Prompt Suspension Law provides that a court, pending prosecution, shall suspend the driver's license, of any person charged with driving while intoxicated, aggravated driving while intoxicated, or driving while ability impaired by the combined influence of drugs or of alcohol and any drug or drugs who, at the time of arrest, is alleged to have had a BAC of .08% or higher as shown by chemical analysis (VTL §1193[2][e][7][a]).

The Zero Tolerance Law is spelled out in VTL §1192-a and provides that it is unlawful for a person under the age of 21 to operate a motor vehicle after having consumed any alcohol (as shown by a BAC of .02% or more). While drivers under 21 remain fully subject to all of the DWI and DWAI provisions and penalties set forth in VTL §1192, a violation of VTL §1192-a is not a criminal offense and subsequent findings and penalties for violation are administrative in nature. These penalties include a civil fine and a license suspension or revocation action.

Leandra's Law is named after Leandra Rosado, an eleven year old girl who was killed in a car crash after the driver, who had allegedly been drinking for several hours prior to the crash, lost control of her vehicle on the Henry Hudson Parkway. Leandra's Law, which became effective December 18, 2009, sets some of the toughest DWI provisions in the country. Under Leandra's Law:

• First time offenders driving while intoxicated or impaired by drugs with a child less than 16 years old in the vehicle may be charged with a class E felony, punishable by up to four years in State prison.
• Courts must order all drivers convicted of driving while intoxicated or aggravated driving while intoxicated to install and maintain an ignition interlock on any vehicle owned and operated by such driver for at least six months.
• Drivers who drive while intoxicated or impaired by drugs and cause the death of a child less than 16 years of age in the vehicle may be charged with a Class B felony, punishable by up to 25 years in State prison.
• Drivers who drive while intoxicated or impaired by drugs and cause serious physical injury to a child less than 16 years of age in the vehicle may be charged with the Class C felony, punishable by up to 15 years in State prison.
• Police must make a notation in the form of "C.I.V." in the "Description of Violation" section of a simplified traffic information if a child less than 16 years of age was present in the vehicle of the person charged with driving while intoxicated, aggravated driving while intoxicated, or driving while ability impaired by drugs. The failure to make such notation, however, does not in any way affect a charge for a violation of the VTL provisions regarding driving while intoxicated.
• Police must report a parent or guardian who is charged with driving while intoxicated or while impaired by alcohol or drugs while their child is a passenger in the vehicle to the Statewide Central Register of Child Abuse and Maltreatment.