Drunk driving in the United States

According to the Bureau of Justice Statistics, approximately 1.5 million drunk driving arrests were made nationwide in 1996. In 1997 an estimated 513,200 DUI offenders were under correctional supervision, down from 593,000 in 1990 and up from 270,100 in 1986.[3]

The Bureau of Justice Statistics estimated that in 1996 local law enforcement agencies made 1,467,300 arrests nationwide for driving under the influence of alcohol, 1 out of every 10 arrests for all crimes in the U.S., compared to 1.9 million such arrests during the peak year in 1983, accounting for 1 out of every 80 licensed drivers in the U.S.[4][5] This represented a 220% increase in DUI arrests from 1970 to 1986, while the number of licensed drivers increased by just 42% in the same period.[6]

The arrest rate for alcohol-related offenses among Native Americans was more than double that for the total population during 1996, and almost 4 in 10 Native Americans held in local jails had been charged with a public order offense, most commonly driving while intoxicated.[7] In 2012, 29.1 million people admitted to driving under the influence of alcohol.[8][9]

Recent analysis has shown cities in which ride sharing services operate show mixed results as to whether the availability of those services affects rates of impaired driving.[10]

Percentage of US traffic collision fatalities where driver blood alcohol level was 0.01 and above, 1999–2012

The risk of having a traffic collision increases with a higher BAC.[11][12]

The National Highway Traffic Safety Administration (NHTSA) estimates that about 18,000 people died in 2006 from alcohol-related collisions, representing 40% of total traffic deaths in the US. Over the decade 2001–2010, this rate showed only a 3% variation, and no trend.[13]

Drivers with a BAC of 0.10% are 6 to 12 times more likely to get into a fatal collision or injury than drivers without positive blood alcohol.[11][12][14] The NHTSA states 275,000 were injured in alcohol-related collisions in 2003.[15] Approximately 60% of the BAC values for motor vehicle collisions are missing or unknown. To analyze what they believe is the complete data, statisticians estimate BAC information.[16]

The NHTSA defines fatal collisions as "alcohol-related" if they believe the driver, a passenger, or non-motorist (such as a pedestrian or pedal cyclist) had a blood alcohol content (BAC) of 0.01% or greater. The NHTSA defines nonfatal collisions as alcohol-related if the crash report indicates evidence of alcohol present, even if no driver or occupant was tested for alcohol.[9] The NHTSA specifically notes that alcohol-related does not necessarily mean a driver or non-occupant was tested for alcohol and that the term does not indicate a collision or fatality was caused by the presence of alcohol.[9] If anyone involved in the crash (even a passenger) has a BAC of 0.01% or greater, then the NTHSA classifies the crash as alcohol-related.[9] Alcohol-related injuries were estimated at 275,000 in 2003.[15]

According to NTSB, 100,000 people have died in alcohol-impaired driving crashes between the NTSB issued its 2013 Reaching Zero report and 2022.[17]

1937 WPA drunk driving poster

New Jersey enacted the first law that specifically criminalized driving an automobile while intoxicated, in 1906. The New Jersey statute provided that "[n]o intoxicated person shall drive a motor vehicle." Violation of this provision was punishable by a fine of up to $500, or a term of up to 60 days in county jail.[18]

Early laws, such as that enacted in New Jersey, required proof of a state of intoxication with no specific definition of what level of inebriation qualified.[19] The first generally accepted legal BAC limit was 0.15%. New York, for example, which had enacted a prohibition on driving while intoxicated in 1910,[20] amended this law in 1941 to provide that it would constitute prima facie evidence of intoxication when an arrested person was found to have a BAC of 0.15 percent or higher, as ascertained through a test administered within two hours of arrest.[21]

In 1938, the American Medical Association created a "Committee to Study Problems of Motor Vehicle Accidents". At the same time, the National Safety Council set up a "Committee on Tests for Intoxication".

In the US, most of the laws and penalties were greatly enhanced starting in the late 1970s, and through the 1990s, largely due to pressure from groups like Mothers Against Drunk Driving (MADD) and Students Against Destructive Decisions (SADD) and activists like Candy Lightner whose 13-year-old daughter Cari was killed by a drunk driver. Zero tolerance laws were enacted which criminalized driving a vehicle with 0.01% or 0.02% BAC for drivers under 21. This is true even in Puerto Rico, despite maintaining a legal drinking age of 18.[22] Research in the American Economic Review suggests that sanctions imposed at BAC thresholds are effective in reducing repeat drunk driving.[23]

On May 14, 2013, the National Transportation Safety Board recommended that all 50 states lower the benchmark for determining when a driver is legally drunk from 0.08 blood-alcohol content to 0.05. The idea is part of an initiative to eliminate drunk driving, which accounts for about a third of all road deaths.[24]

In 2022, this BAC reduction was implemented by Utah with success when some states failed and other did not try to implement BAC reduction.[25]

After the passage of federal legislation, the legal limit for commercial drivers is now set at 0.04%. The Federal Motor Carrier Safety Administration (FMCSA) regulation prohibits those who hold a commercial driver's license from driving with an alcohol concentration of 0.04 or greater. A commercial driver with an alcohol concentration of 0.02 or greater, but less than 0.04, must be removed from duty for 24 hours.[26]

In 2016, the Supreme Court of the United States, in Birchfield v. North Dakota, held that both breath tests and blood tests constitute a search under the Fourth Amendment, concluding that requiring breath tests is constitutional without a search warrant; however, requiring more intrusive blood tests involving piercing the skin is not, as the goal of traffic safety can be obtained by less invasive means.[27]

In construing the terms DUI, DWI, OWI and OVI, some states make it illegal to drive a motor vehicle while under the influence or driving while intoxicated while others indicate that it is illegal to operate a motor vehicle. There is a split of authority across the country regarding this issue. Some states permit enforcement of DUI, DWI, and OWI/OVI statutes based on "operation and control" of a vehicle, while others require actual "driving". "The distinction between these terms is material, for it is generally held that the word 'drive,' as used in statutes of this kind, usually denotes movement of the vehicle in some direction, whereas the word 'operate' has a broader meaning so as to include not only the motion of the vehicle, but also acts which engage the machinery of the vehicle that, alone or in sequence, will set in motion the motive power of the vehicle." (State v. Graves (1977) 269 S.C. 356 [237 S.E.2d 584, 586–588, 586. fn. 8]

All states in the U.S. designate a "per se" blood or breath alcohol level as the threshold point for an independent criminal offense. This is often referred to as the "legal limit". It is a permissive presumption of guilt where the person's BAC is 0.08% or greater (units of milligrams per deciliter, representing 8 g of alcohol in 10 liters of blood).[28] Some states (e.g., Colorado) include a lesser charge, sometimes referred to as "driving while ability impaired" that may apply to individuals with a 0.05% or above, but less than the 0.08% per se limit for the more serious charge.[28]

All states have a "catch-all" provision designed to cover those circumstances where the person is below 0.08%, but the person still appears impaired by definition of law. These types of "catch-all" statutes cover situations involving a person under the influence of drugs or under the combined influence of alcohol and drugs. With the advent of the legalization of marijuana, these catch-all provisions cover those prosecutions pursuing those charged with driving under the influence of drugs or even drugs and alcohol.

All US states have implied consent laws which state that a licensed driver has given their consent to an evidential breathalyzer or similar manner of determining blood alcohol concentration;[29] however, in order to sustain a conviction based on evidence from a chemical test, probable cause for arrest must be demonstrated.

Every state has enhanced penalties for refusing to submit to an Implied Consent Test pursuant to the State's Implied Consent Laws. In California, refusing to submit to a test of one's breath or blood upon being arrested for driving under the influence carries an additional punishment of a one-year license suspension pursuant to California Vehicle Code Section 13558(c)(1).[30]

Approximately twenty to thirty states have criminalized impaired riding of a bicycle, whereas others have no sanctions relevant to cycling.[31][32] Most such laws extend driving laws to all vehicles ("all vehicles" as opposed to "motor vehicles"), but a few address impaired bike riding separately. In some states, enhanced penalties are automobile-specific. Some states, notably Oregon, do not extend the implied consent law to cyclists.[31] While police activities targeting impaired cyclists are rare, a cyclist could encounter police in a circumstance where the cyclist would otherwise be ticketed.[nb 1]

Six states require physicians to report patients who drive while impaired.[35] Another 25 states permit physicians to violate doctor-patient confidentiality to report impaired drivers, if they so choose.[35] The American Medical Association endorsed physician reporting in 1999, but deferred to the states on whether such notification should be mandatory or permissive.[35] Medical bioethicist Jacob Appel of New York University says physician reporting may deter some patients from seeking care, writing "Reporting may remove some dangerous drivers from the roads, but if in doing so it actually creates other dangerous drivers, by scaring them away from treatment, then society has sacrificed confidentiality for no tangible return in lives saved."[35]

The penalties for drunk driving vary among states and jurisdictions. It is not uncommon for the penalties to be different from county to county within any given state depending on the practices of the individual jurisdiction. Some jurisdictions require jail time and larger fines, even on a first offense. For instance, Ohio requires a mandatory 72-hour jail sentence for a first offense conviction; however, the jail time component is satisfied by attendance of the Ohio A.W.A.R.E. Program, which is a 72-hour alcohol-education program. Compared to many other countries, such as Sweden, penalties for drunk driving in the United States are considered less severe unless alcohol is involved in an incident causing injury or death of another, such as DUI, DWI or OWI with Great Bodily Injury (GBI) or Vehicular Manslaughter.

The State of Washington used to permit those charged with a first offense drunk driving to complete a diversion program that resulted in the charges being dismissed upon the completion of a Diversion Program. In 1975, under the revised code of Washington or RCW Section 10.05, the Washington State Legislature established a deferred prosecution option for offenders arrested for driving under the influence of alcohol or impairing drugs (DUI). It was intended to encourage individuals to seek appropriate treatment and, under this option, defendants with a significant alcohol or drug dependence problem could petition a court to defer disposition of their charge until they have completed intensive substance dependence treatment and met other conditions required by the court. If the defendant successfully completed the terms of the program, the charge was dismissed; for those who failed, the deferred status was revoked and the defendant was prosecuted for the original DUI charge. (RCW 10.05.010 and 10.05.020) In 1992, the University of Washington Alcohol and Drug Abuse Institute evaluated DUI deferred prosecution and concluded the program reduced DUI recidivism.[36] In 1998, the legislature modified the DUI statutes. Among other things, the length of deferred prosecution supervision was increased from two to five years and defendants were restricted to one deferred prosecution per lifetime.

These innovative courts use substance abuse intervention with repeat offenders who plead guilty to driving while intoxicated. Those accepted into the diversionary program are required to abstain from alcohol. Some are required to wear a device that monitors and records any levels of alcohol detected in their bloodstreams.

The federal Assimilative Crimes Act, which makes state law applicable on lands reserved or acquired by the Federal government when the act or omission is not made punishable by an enactment of Congress, recognizes collateral actions related to DUI convictions as punishments. According to 18 U.S.C. § 13:

… that which may or shall be imposed through judicial or administrative action under the law of a State, territory, possession, or district, for a conviction for operating a motor vehicle under the influence of a drug or alcohol, shall be considered to be a punishment provided by that law …

An SR-22 is an addendum to an insurance policy. It is an administrative form that attests to an insurance company's coverage, or the posting of a personal public bond in the amount of the state's minimum liability coverage for the licensed driver or vehicle registration. The SR in SR-22 stands for Safety Responsibility, and it is needed to reinstate a suspended driver's license after a DUI conviction in 49 states and the District of Columbia. It is submitted to the State's DMV by an auto insurance company to serve as proof that a driver has the minimum liability insurance that the states requires. They are essentially an agreement between a driver's insurance company and the respective State's DMV that requires the driver's insurance company to notify the respective State's DMV that the driver's insurance has either been terminated or lapsed; thus instituting a suspension of the driver's driving privileges until proof of insurance is re-filed with the State's DMV.

While SR-22s are typically filed with the respective State's DMV, some States require the driver to carry proof of the SR-22 or to carry it in the registered vehicle, (particularly if the driver has been cited for coverage lapses or other administrative infractions). SR-22s may attest coverage for a vehicle regardless of operator (owner liability coverage), or cover a specific person regardless of the specific vehicle operated (operator liability coverage).

As stated, the form is required in 49 states and the US District of Columbia in order to register a vehicle for usage on public roads. It is also required to redeem a license which has been suspended due to coverage lapse in these required states. These states also, generally, require that the issuing insurance company provide the relevant state's DMV with timely updates as to the status of such coverage. If the policy with the SR22 cancels, a form called an SR26 is issued and sent to the state DMV.[37] Upon notice that there has been a lapse in coverage, the state will suspend the driver's license again.[38] Another SR-22 filing will need to be submitted to regain driving privileges.

Every jurisdiction imposes the completion of alcohol education programs, commonly known as DUI programs, subsequent to a DUI/DWI/OWI conviction. Additionally, some states impose an additional requirement that a person attend a Victim Impact Panel (VIP) administered by Mothers Against Drunk Driving (MADD), which was established in 1982. Both DUI classes and Victim Impact Panels are available in some states for first offense DUIs dependent on the judge's decision.[39]

Ohio DUI plate

Minnesota drunk driver plate

By comparison, a regular Minnesota plate has colored graphics.

In 1967, Ohio began to issue special license plates to DUI offenders who are granted limited driving privileges such as work-related driving until a court can rule that they can have full privileges back. In 2004, the plates became mandated by state law to all DUI offenders.[40] Unlike Ohio's standard-issue plates (which as of 2008 have a picture of the Ohio countryside), the DUI plates are yellow with red writing with no registration stickers or graphics. They are commonly referred to as "party plates".[40]

Minnesota has a similar program, where the plates are white with either blue or black text. The plate number is a "W", followed by a letter and four numbers. These plates may be issued to drivers with at least two offenses in a five-year period; three offenses in a ten-year period; having a BAC twice the legal limit; or having a child in the car at the time of arrest.[41] In Minnesota, DUI plates are referred to as "whiskey plates",[42] whiskey being the name of the letter W in the NATO phonetic alphabet.

Most states impose the installation of ignition interlock devices (IID), with varying thresholds for installation requirements.[43][44] Criminal process thresholds for installation requirements vary between minimum BAC levels (e.g., 0.20%, or 0.15%) or repeat offense, with about half of the states requiring installation on first offense.

These ignition interlock sanctions are meant as punishment, but also as a deterrence. When required under a high BAC level or multiple offense threshold, ignition interlock requirements address a strong tendency of repeat offense by drivers with alcoholic use disorder (AUD or alcoholism).

Ignition interlock requirements are also imposed in some instances after positive chemical blood alcohol tests, as a physical deterrent for drivers with alcoholic use disorder, or as a pseudo-civil punishment. Ignition interlock requirements are also imposed in some instances after an implied consent refusal under similar forensic procedures.

In most US implementations, IIDs are set to a "zero tolerance" level (set to either levels consistent with culinary alcohol or measurement errors). Violations can occur from a driver exceeding the "zero tolerance" level, but can also occur from use by other drivers within legal limits, or from test anomalies. In some states, anomalies are routinely discounted, for example as not consistent with patterns of BAC levels or at levels incompatible with life (e.g., significant mouth alcohol - which as BAC would be fatal). In some states, "fail" readings not consistent with actual alcohol use can be cleared by a routine process, but other states automatically deem these "fail" readings as violations.

In operation, the driver blows into the IIDs to enable the car's starter. After a variable time period of approximately 20–40 minutes, the driver is required to re-certify (blow again) within a time period consistent with safely pulling off the roadway. If the driver fails to re-certify within the time period, the car will alarm in a manner similar to setting off the car's immobilizer (but mechanically independent of the immobilizer).

Various US states have different penalties for disabling IIDs. In some cases, the driver may be penalized if a family member or mechanic disables the IID when not in use by the sanctioned individual, or temporarily for servicing the vehicle. In some implementations, disabling by mechanics and others is either permitted or authorisation easily obtained, but some jurisdictions restrict or deny authorisation. (Such restrictions on mechanics can be problematic, for example, if limited to designated "licensed mechanics" or as applied to routine repair procedures requiring operation of the ignition and starter systems.) Some jurisdictions criminalize such temporary bypass of IIDs.

Proposals (none official) have been made to install IIDs on all new vehicles, set to the legal limit for the driver. Issues to be solved, besides consumer and voter acceptance, include difficulty in obtaining accurate measurements without inconvenience, and a need to achieve Six Sigma (6σ) reliability,[45] in order to not interfere with vehicle usability.

There are no present plans to introduce universal IID installation in the US.

Some states, such as California, allow for the impoundment and forfeiture of vehicles under certain conditions.[46][47]

Following are common procedures when a law enforcement officer has reason to suspect a driver is intoxicated. While local procedures vary under the tens of thousands of courts in the US having traffic jurisdiction, the basic procedure is:

1. reasonable suspicion

2. probable cause

3. arrest (including invoking the implied consent law)

4. criminal charge and "civil law" sanctions[48]

The legal stages are relevant because of the degree of evidence required at each stage. (For example, the police need not demonstrate guilt "beyond a reasonable doubt" in order to execute a traffic stop.)

The investigation and NHTSA "phases" are distinct from the legal stages of the police arrest process. Instead, the investigation has, as its purpose, to take the process from initial contact through all of the evidence stages, through to prosecution. The primary goals are to:

• Identify impaired drivers;
• Establish clear probable cause for arrest, which is necessary to sustain the use of chemical test results in court. Without probable cause, the chemical test results are subject to the exclusionary rule
• Proceed to obtain proof of intoxication, typically using chemical test results.

According to the National Highway Traffic Safety Administration, police officers should conduct DUI Investigations according to a specific protocol called phases. According to the NHTSA training, DUI Investigations are categorized by these phases:

• Phase 1 - "Vehicle in Motion"
• Phase 2 - "Personal Contact"
• Phase 3 - "Pre-Arrest Screening"

The "Vehicle in Motion" Phase deals with the law enforcement officers' observations of the suspect's driving maneuvers. The "Personal Contact" Phase is where the officer actually comes into contact with the suspected impaired driver. The "Pre-Arrest Screening" Phase is portion of the DUI Investigation that encompasses the Pre-Field Sobriety Test Questioning and the Field Sobriety Testing, including a Preliminary Alcohol Screening Test where applicable. This Phase also includes the post-arrest evidentiary chemical test despite that it occurs subsequent to a DUI arrest, not prior to a DUI arrest.

The officer will typically approach the driver's window and ask some preliminary questions. During this phase of the stop, the officer will note if they detect any of the following indicators of intoxication:

• Odor of an alcoholic beverage on the driver's breath or in the car generally
• Slurred speech in response to the questioning
• Watery, blood shot, or reddish eyes
• Flushed face
• Droopy eyelids
• Difficulty in understanding and responding intelligently to question
• Fumbling with his or her driver's license and registration
• The plain-view presence of containers of alcoholic beverages in the vehicle
• Admission of consumption of alcoholic beverage

If the officer observes enough to have a reasonable suspicion to legally justify a further detention and investigation, they will ask the driver to step out of the vehicle, and request that the driver submit to voluntary field sobriety tests.

Note: Local terminology will vary, but these general classifications fall under US Supreme Court guidelines.

Each stage has different requirements for establishing a basis for police or prosecutorial action. Without establishing that basis, the process is illegal and can cause a prosecution to fail under the exclusionary rule.

The police must have a reason to engage in a traffic stop. This typically involves either observing a traffic violation or observing behavior, such as weaving or lane departure, that would raise a "reasonable suspicion" of driving while impaired. The police must have an articulable reason for the stop, but does not need probable cause for an arrest.

One exception is a roadblock (where legal). Roadblocks do not involve reasonable suspicion, but must meet particular legal standards to avoid arbitrariness while still assuring randomness.

During the traffic stop, the police will attempt to obtain sufficient evidence to support "probable cause". This includes asking questions, and requesting further evidence or confession.

There are several situations in which the officer will come into contact with a driver, some examples are:

• The officer on patrol has observed erratic, suspicious driving, or a series of traffic infractions indicating the possibility that the driver may be impaired. This is by far the most common reason for stopping a suspect.
• A police officer has stopped a vehicle for a lesser traffic offense, notices the signs of intoxication, and begins the DUI investigation.
• The driver has been involved in an automobile collision; the officer has responded to the scene and is conducting an investigation.
• The driver has been stopped at a sobriety checkpoint (also known as roadblocks).
• The police have received a report, possibly from an anonymous citizen, that a described car has been driving erratically. The officer should verify the erratic driving before pulling the driver over. In some cases, the driver will no longer be in the vehicle.

The following list of DUI symptoms, from a publication issued by the National Highway Traffic Safety Administration (DOT HS-805-711),[49] is widely used in training officers to detect drunk drivers. After each symptom is a percentage figure which, according to NHTSA, indicates the statistical chances through research that a driver is over the legal limit.

If the officer observes enough evidence to have a "Reasonable Suspicion" to legally justify a further detention and investigation, they will ask the driver to step out of the vehicle.

"Probable cause" is established by obtaining evidence from the police encounter sufficient to meet the "probable cause" standard for arrest. "Probable cause" is not necessarily sufficient to obtain a conviction, but is a prerequisite for arrest. Examples of "probable cause" for a drunk driving arrest includes:

1. Observation

The NHTSA outlines several indicators of impairment, commonly referred to as “impairment cues.” These cues encompass behaviors like tightly gripping the steering wheel, driving with a closely positioned face to the windshield, slouching in the seat, and maintaining a fixed stare straight ahead. Certain officers regularly observe the facial expressions of drivers in opposing traffic, seeking signs of impairment.[50]

2. Confession of having consumed alcohol in the recent past. Relevant examples of confessions:

• "I had a glass of wine."
• "I was at a friend's party."
• "I was at the Stone Balloon."

The confession is the easiest way to establish "probable cause", and police know that social convention encourages people to respond to police questions. While it is inadvisable to lie to police, the suspect has the option to "respectfully decline" to answer questions.[51][52]

The suspect is typically not given Miranda warnings at this time because the encounter legally has not gone from "investigatory" to "accusatory", and because the police want the suspect to believe the questions are not being made to gather "probable cause" evidence. At this point, the suspect is not required to provide more than identification and vehicle information.

3. Documented test results, such as

• Preliminary breath test (PBT) evidence
• Pseudo-scientific test results from field sobriety tests

Main article: Field sobriety testing

Police administer a one-leg-stand test after a crash.

One of the most controversial aspects of a DUI stop is the field sobriety test (FSTs). The National Highway Traffic Safety Administration (NHTSA) has developed a model system for managing Standardized Field Sobriety Test (SFST) training.

The NHTSA have published numerous training manuals associated with FSTs.[53] As a result of the NHTSA studies, the walk-and-turn test was determined to be 68% accurate, and the one-leg stand test is only 65% accurate when administered to people within the study parameters. The tests were not validated for people with medical conditions, injuries, 65 years or older, and 50 pounds or greater overweight. The officer will administer one or more field sobriety tests. FSTs are considered "divided attention tests" that test the suspect's ability to perform the type of mental and physical multitasking that is required to operate an automobile. However, these tests can be problematic for people with non-obvious disabilities affecting proprioception (the awareness of the body's movement), such as Ehlers-Danlos syndrome.

The three validated tests by NHTSA are:

1. The Horizontal Gaze Nystagmus Test, which involves following an object with the eyes (such as a pen) to determine characteristic eye movement reaction.[54]
2. The Walk-and-Turn Test (heel-to-toe in a straight line). This test is designed to measure a person's ability to follow directions and remember a series of steps while dividing attention between physical and mental tasks.
3. The One-Leg-Stand Test

According to NHTSA, these tests were not designed to measure impairment, but rather to give a probability that a driver is at or above a 0.08% BAC. However, studies have shown that there are reasons to doubt the tests' usefulness in helping an officer to make such a determination. In 1991, Dr. Spurgeon Cole of Clemson University conducted a study of the accuracy of FSTs. His staff videotaped people performing six common field sobriety tests, then showed the tapes to 14 police officers and asked them to decide whether the suspects had "had too much to drink and drive" (sic). The blood-alcohol concentration of each of the 21 DUI subjects was 0.00, unknown to the officers. The result: the officers gave their opinion that 46% of these innocent people were too drunk to be able to drive. This study showed the possible inaccuracy of FSTs.[55]

Alternative tests, which have not been scientifically validated, include:

• Romberg test, or the Modified-Position-of-Attention Test, (feet together, head back, eyes closed for thirty seconds).
• The Finger-to-Nose Test (tip head back, eyes closed, touch the tip of nose with tip of index finger).
• The Alphabet Test (recite all or part of the alphabet).
• The Finger Count Test (touch each finger of hand to thumb counting with each touch (1, 2, 3, 4, 4, 3, 2, 1)).
• The Counting Test (counting backwards from a number ending in a number other than 5 or 0 and stopping at a number ending other than 5 or 0. The series of numbers should be more than 15).
• The Preliminary Alcohol Screening Test, PAS Test or PBT, (breathe into a "portable or preliminary breath tester", PAS Test or PBT).

FSTs and SFSTs are promoted as, "used to determine whether a subject is impaired",[56][57] but FST tests are widely regarded having, as their primary purpose, establishing tangible evidence of "probable cause for arrest".[58][59][60][57] Probable cause is necessary under US law (4th Amendment) to sustain an arrest and (significantly) to invoke the implied consent law.

A secondary purpose is to provide supporting corroborative tangible evidence for use against the suspect for use at trial in jurisdictions that permit such evidence.[61]

In all US jurisdictions, participation in a Field Sobriety Test (FST) is voluntary, and not required under implied consent laws.[29] (Police are not obliged to advise the suspect that participation in a FST or other pre-arrest procedures is voluntary. In contrast, formal evidentiary tests given under implied consent requirements are considered mandatory.)[62]

A suspect requested to participate in a FST is likely to be told that the purpose is to determine whether the suspect is impaired;[56][57] however, FST tests are widely regarded having, as their primary purpose, gaining tangible evidence for use against the suspect in the establishment of probable cause for arrest.[59][60]

An increasingly used field sobriety test involves having the suspect breathe into a small, handheld breath testing device. These are often referred to as PAS Tests, or "Preliminary Alcohol Screening" Tests", or a PBT, "Preliminary Breath Test" and precede the actual arrest and subsequent requirement to submit to an evidentiary chemical test of the suspect's breath or blood. These breath testing devices used are smaller, inexpensive versions of the larger, more sophisticated instruments at the police stations, commonly known as an Evidentiary Breath Test using an EBT device, or Evidentiary Breath Test device. An increasing number jurisdictions began using Portable Evidentiary Breath Test devices, or PEBT devices, that are more sophisticated versions of the smaller, inexpensive versions of the larger, larger instruments at the police stations. Another distinction is that, while the larger EBTs usually employ infrared spectroscopy, the PEBT and PAS devices use a relatively simple electrochemical (fuel cell) technology. When used for purposes of a Preliminary Alcohol Screening Test, or PAS Test, their purpose, along with the other FSTs, is to assist the officer in determining whether he/she has probable cause for arrest.

The Preliminary Breath Test (PBT) or Preliminary Alcohol Screening test (PAS) is sometimes categorised as part of field sobriety testing, although it is not part of the series of performance tests. The PBT (or PAS) uses a portable breath tester. While the tester provides numerical blood alcohol content (BAC) readings, its primary use is for screening and establishing probable cause for arrest, to invoke the implied consent requirements. In US law, this is necessary to sustain a conviction based on evidential testing (or implied consent refusal).[62] Regardless of the terminology, in order to sustain a conviction based on evidential tests, probable cause must be shown (or the suspect must volunteer to take the evidential test without implied consent requirements being invoked).[62]

Police are not obliged to advise the suspect that participation in a FST or other pre-arrest procedures is voluntary. In contrast, formal evidentiary tests given under implied consent requirements are considered mandatory.[62]

Refusal to take a preliminary breath test (PBT) in Michigan subjects a non-commercial driver to a "civil infraction" penalty, with no violation "points",[63] but is not considered to be a refusal under the general "implied consent" law.[64] In some states, the state may present evidence of refusal to take a field sobriety test in court, although this is of questionable probative value in a drunk driving prosecution.

Different requirements apply in many states to drivers under DUI probation, in which case participation in a preliminary breath test (PBT) may be a condition of probation, and for commercial drivers under "drug screening" requirements. Some US states, notably California, have statutes on the books penalizing PBT refusal for drivers under 21; however the Constitutionality of those statutes has not been tested. (As a practical matter, most criminal lawyers advise not engaging in discussion or "justifying" a refusal with the police.)

If the officer has sufficient probable cause that the suspect has been driving under the influence of alcohol, they will make the arrest, handcuff the suspect and transport them to the police station. En route, the officer may advise them of their legal implied consent obligation to submit to an evidentiary chemical test of blood, breath or possibly urine depending on the jurisdiction.

Laws relating to what exactly constitutes probable cause vary from state to state. In California it is a refutable presumption that a person with a BAC of 0.08% or higher is driving under the influence. However, section 23610(a)(2) of the California Vehicle Code states that driving with a BAC between 0.05% and 0.08% "shall not give rise to any presumption that the person was or was not under the influence of an alcoholic beverage".

An arrestee will be offered a chemical test of breath, blood or, much less frequently, urine. Breath test results are usually available immediately; urine and blood samples are sent to a lab for later analysis to determine the BAC or possible presence of drugs. Some states sought to impose criminal punishment for a refusal to submit to a chemical test of his/her breath or blood; however, in Birchfield v. North Dakota, the United States Supreme Court visited the issue of whether states can criminalize a refusal to submit to a chemical test. The United States Supreme Court decided that states may criminalize a refusal to submit to a breath test; but not a refusal to submit to a blood test absent a McNeely warrant, named after Missouri v. McNeely (2013). This was a case decided by United States Supreme Court, on appeal from the Supreme Court of Missouri, regarding exceptions to the Fourth Amendment to the United States Constitution under exigent circumstances.[65] The United States Supreme Court ruled that police must generally obtain a warrant before subjecting a drunken-driving suspect to a blood test, and that the natural metabolism of blood alcohol does not establish a per se exigency that would justify a blood draw without consent.

Regarding blood tests, some commentators, such as Brown University's Jacob Appel, have criticized the role of medical personnel in this process. According to Appel, "If physicians acquiesce today in the removal of a resistant patient's blood, soon they may be called upon to pump the contents of an unwilling patient's stomach or even to perform involuntary surgery to retrieve an evidentiary bullet."[66]

While chemical tests are used to determine the driver's BAC, they do not determine the driver's level of impairment. However, state laws usually provide for a rebuttable legal presumption of intoxication at a BAC of 0.08% or higher (see blood alcohol test assumptions).

If it is determined after arrest that the person's BAC is not at or above the legal limit of 0.08%, they will probably be released without any charges. One may, however, still be charged with driving under the influence of alcohol on the basis of driving symptoms, observed impairment, admissions or performance on the field sobriety tests. And if there is suspicion of drug usage, a blood or urine test is likely, or at least the testimony of a specially trained officer called a Drug Recognition Expert (DRE). Assuming sufficient evidence of impaired driving from drugs, the arrested may face charges of driving under the influence of drugs or the combined influence of alcohol and drugs.

Most of the time, the driver will either be kept in a holding cell (sometimes referred to as the "drunk tank") until they are deemed sober enough to be released on bail or on his "own recognizance" (OR). A date to appear in court for an arraignment will be given to them. If they cannot make bail or is not granted OR, they will be kept in jail to wait for the arraignment on remand.