DUI laws were created in 1906, when New Jersey became the first state to make it a crime to drive a motor vehicle while intoxicated. Massachusetts and New York followed by 1910, and California and other states adopted similar statutes shortly afterward. Every piece of modern drunk driving law, from breath tests to the 0.08 percent limit to ignition interlocks, traces back to that first short sentence of New Jersey law and the century of refinement that followed.
The 1906 New Jersey Statute
New Jersey’s law was blunt: “No intoxicated person shall drive a motor vehicle.” It set no blood alcohol threshold and left officers to judge impairment by watching a driver walk, listening for slurred speech, or smelling alcohol. Violators faced fines up to $500 and up to 60 days in county jail.
The early statutes in Massachusetts, New York, California, and elsewhere shared the same weakness. None of them defined what “intoxicated” actually meant in measurable terms. One officer might arrest a driver another would wave through, and prosecutors had little objective evidence to present in court.
When Blood Alcohol Limits Replaced Guesswork
The first objective standard arrived in 1938, when the American Medical Association and the National Safety Council recommended 0.15 percent blood alcohol concentration as the threshold for legal intoxication. That number sounds high today, but it gave courts and police an objective benchmark for the first time, and many states adopted it.
Research over the following decades showed impairment begins well below 0.15 percent, and states gradually lowered their limits. By the late 1990s the debate was between 0.10 and 0.08 percent. In 2000, only 19 states had adopted 0.08 percent. Congress then passed legislation requiring all states to adopt that limit by October 2003 or lose a portion of their federal highway construction funding.1Office of the Law Revision Counsel. 23 U.S. Code 163 – Safety Incentives to Prevent Operation of Motor Vehicles by Intoxicated Persons By 2004, every state had complied, making 0.08 percent the nationwide standard for drivers 21 and older.2The Community Guide. Lowering Legal Blood Alcohol Limits Saves Lives
The Drunkometer and the Breathalyzer
A BAC limit is only useful if police can measure alcohol in the field. Rolla N. Harger, a biochemistry professor at Indiana University, invented the Drunkometer in 1931 and patented it in 1936. A suspect blew into a balloon, and the breath passed through a chemical solution that changed color in the presence of alcohol. Crude, but it brought science into what had been a subjective process.
Robert Borkenstein, an Indiana State Police officer who had worked with Harger, built on the concept and invented the Breathalyzer in 1954. It was smaller, more portable, and more reliable, and Borkenstein demonstrated it publicly at the National Safety Congress in Chicago that year. The Breathalyzer became the standard roadside tool for decades. Modern evidential breath testing instruments have replaced it, but the basic principle traces directly to Borkenstein’s work.
Implied Consent Laws
Testing technology raised a follow-up question: what happens when a driver refuses? Starting in the 1950s and 1960s, states began passing implied consent laws. The premise is simple. By driving on public roads, you’ve already agreed to submit to chemical testing if an officer has reasonable grounds to suspect impairment. Refuse, and you face automatic administrative penalties, typically a license suspension of six months to a year for a first refusal and longer for repeat offenders. Those penalties are handled through the DMV rather than the courts, so they apply whether or not you’re ever convicted of a DUI.
The U.S. Supreme Court drew a line around implied consent in 2016. In Birchfield v. North Dakota, the Court ruled that states can require warrantless breath tests after a lawful DUI arrest but cannot criminalize a driver’s refusal to submit to a blood test without a warrant.3Justia Law. Birchfield v North Dakota, 579 US (2016) A blood draw is a more invasive search, which is why it gets different treatment. Every state now has some form of implied consent law, though specific penalties and procedures differ.
MADD and the Federal Funding Lever
Before 1980, DUI laws were almost entirely a state-by-state matter, and many states treated drunk driving as a minor traffic offense. That changed when Candy Lightner founded Mothers Against Drunk Driving in 1980, after her 13-year-old daughter Cari was killed by a repeat drunk driver in California. MADD organized volunteers nationwide, marched on state capitols, and made drunk driving a politically unavoidable issue. Within a few years, every state was tightening its laws.
Washington backed that momentum with money. In 1984, President Reagan signed the National Minimum Drinking Age Act, which threatened to withhold highway funding from any state that allowed people under 21 to purchase or publicly possess alcohol.4Office of the Law Revision Counsel. 23 USC 158 – National Minimum Drinking Age Every state eventually raised its drinking age to 21. Congress used the same playbook a decade later with the 0.08 percent BAC mandate and again in 1995 with zero-tolerance laws for young drivers.
Zero Tolerance for Drivers Under 21
The National Highway Systems Designation Act of 1995 required states to set a BAC limit of 0.02 percent or lower for drivers under 21, or lose federal highway funds beginning in fiscal year 1999. Since it’s already illegal for someone under 21 to drink, any detectable alcohol while driving should trigger a DUI charge. All 50 states now have zero-tolerance laws, and many set the limit at 0.00 or 0.01 percent rather than the federal floor of 0.02.
Standardized Field Sobriety Tests
Even with breath testing devices, officers still needed reliable ways to assess impairment on the roadside before making an arrest. In the late 1970s, the National Highway Traffic Safety Administration funded research to develop a standardized battery of tests. Between 1978 and 1981, researchers validated three as the most reliable indicators of impairment: horizontal gaze nystagmus (watching for involuntary eye movement), the walk-and-turn, and the one-leg stand. NHTSA adopted them as the Standardized Field Sobriety Test battery, and they remain the foundation of roadside impairment assessment today. Administered correctly, they give officers both probable cause for arrest and evidence that holds up in court.
The Push Toward 0.05 Percent
The 0.08 percent standard may not be the final word. In 2018, Utah became the first state to lower its limit to 0.05 percent. An NHTSA study found that in 2019, the first full year under the new limit, Utah’s fatal crash rate dropped 19.8 percent, far outpacing the 5.6 percent reduction seen across the rest of the country.5NHTSA. Utah’s .05% Law Shows Promise to Save Lives, Improve Road Safety Neighboring states with unchanged laws didn’t see comparable improvements. Alcohol-related arrests in Utah actually declined slightly, suggesting the lower limit changed drinking-and-driving behavior rather than simply catching more people.
No other state has followed yet, though several have introduced bills. The National Transportation Safety Board has recommended 0.05 percent as a national standard, and more than 100 countries already use it.
Drug-Impaired Driving Laws
Alcohol isn’t the only substance that impairs drivers, and the spread of marijuana legalization has forced states to confront a problem that doesn’t have a clean solution. Unlike alcohol, there’s no universally accepted BAC-equivalent for THC or other drugs. States have taken widely different approaches. Sixteen states impose zero-tolerance rules for one or more drugs. Five states set specific per se concentration limits. Eighteen states have some form of zero-tolerance or per se limit targeting marijuana specifically.6Governors Highway Safety Association. Drug-Impaired Driving
Enforcement is difficult. THC metabolites can linger in blood and urine for weeks after the impairing effects have worn off, so a positive test doesn’t necessarily mean the driver was high at the time. Several states are experimenting with oral fluid roadside testing, which screens saliva for six drug categories including THC, opiates, and amphetamines. These devices are newer than breath testing for alcohol and face ongoing legal challenges about their admissibility.
Ignition Interlocks and Continuous Monitoring
The most significant recent shift has been the move from punishing impaired driving after the fact to physically preventing it. Ignition interlock devices require a driver to blow into a breath sensor before the vehicle will start. If the device detects alcohol above a preset limit, the car won’t turn on. As of 2024, 31 states and the District of Columbia require interlocks for all convicted DUI offenders, including first-time offenders.7NCSL. State Ignition Interlock Laws The federal government encourages the trend by allocating grant money to states that adopt interlock programs through the national priority safety programs under federal highway safety law.8Office of the Law Revision Counsel. 23 USC 405 – National Priority Safety Programs
Courts also increasingly order continuous alcohol monitoring bracelets for DUI offenders on probation. These ankle-worn devices measure alcohol in sweat around the clock and transmit data to a monitoring center. If the system detects a drinking event, it alerts the court or probation officer. Violations can lead to anything from a warning to jail time, depending on the terms of the court order.
Alcohol-impaired driving killed roughly 25,000 Americans a year in 1980; by 2023, that number had dropped to about 12,429, still accounting for 30 percent of all traffic fatalities.9NHTSA. 2023 Data: Alcohol-Impaired Driving Each generation of DUI law since 1906 has addressed a weakness in the last, and the direction has been consistent: tighter thresholds, better evidence, and now technology that stops impaired driving before the car moves.