Today's DUI and Its Evolution

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Driving under the influence (DUI) used to be simple—if you were drunk, you went to jail. But now the DUI has evolved to deal with an avalanche of recreational and prescription drugs that could be worse than hard liquor. But is the law changing for the better?

DUI laws started in New York in 1910. Alcohol was illegal under the prohibition, so the zero-tolerance policy should have been simple, but the lack of reliable tests meant convictions were often overturned.

There were no drugged driving laws, which meant patrons could buy heroin, cocaine chloroform, and morphine at the local drugstore. Drugged driving, then, has been with us since the Ford Model T.

Introducing the Drunkometer 

The first Blood Alcohol Content (BAC) level came into force in 1938 after Doctor Harger, the National Safety Council, and the American Medical Association created a machine called the Drunkometer. They set the legal limit at 0.15% (BAC), a number that has since come down.

The Breathalyzer followed in 1953 thanks to retired police officer Robert Borkenstein. Suddenly we had a roadside test, and yet still, to this day, some states solely stick with the field sobriety test. But, we now face a different landscape.

Tackling a Growing Problem

Drunk driving is just one part of the puzzle. Increased illegal, semi-legal, and prescription drug use is putting U.S. drivers at risk.

According to the 2014 National Survey on Drug Use and Health (NSDUH), 27.7 million people over the age of 16 drove under the influence of alcohol in the previous year, while 10.1 million people admitted to driving under the influence of drugs.

It’s difficult to determine how specific drugs affect driving because people tend to mix various substances, including alcohol, the National Institute on Drug Abuse says. What we do know, however, is that even small amounts of some drugs can have a measurable effect. As a result, some states have zero-tolerance laws for drugged driving. This means a person can face DUI charges if there is any amount of drug in the blood or urine. It's important to note that many states are waiting for research to better define blood levels that indicate impairment, such as those they use with alcohol.

Struggling to Set Limits

Just like in the early days of alcohol, separate states are struggling to define safe limits. Sixteen states have adopted a zero-tolerance policy. Five states have put firm limits on the amount of tetrahydrocannabinol (THC)—the primary psychoactive constituent of marijuana—that’s acceptable for a driver to have in his or her system, but there’s no common policy.

Some studies show that taking marijuana increases the likelihood of a crash, but the benchmark NHTSA study showed there was no significant risk attached to driving while high.

Since Washington state legalized possession of up to one ounce of marijuana, the AAA Foundation study revealed a sharp increase in drivers using it. The study also estimated that 10% of fatal incidents between 2010 and 2014 in Washington state involved marijuana.

There’s a definite spike, nine months after the drug was legalized. The only problem with drawing conclusions from this data is that 66% of the 303 drivers that lost their lives were on a cocktail of drugs. What that means: 39% had alcohol in their bloodstream, 16.5% had at least trace elements of other drugs, and 10.5% had both alcohol and other drugs in their blood.

Is Marijuana a Problem?

So, even with a limit on the THC or metabolytes in their system, some of these drivers would have slipped under the radar of the most reliable test. Singling out marijuana, then, doesn’t seem to be the answer.

With many states now legalizing marijuana, the DUI rules get even murkier. Massachusetts recently passed a bill allowing recreational use, but at the same time announced a crackdown on drug driving. It favors a Field Sobriety Test and is training officers to spot the signs of a driver under the influence of THC.

The state points to the 2.7% increase in accidents in Colorado, Washington, and Oregon as justification. That number comes from the Insurance Institute of Highway Safety, but the American Journal of Public Health conducted its own study and proved there was no correlation between marijuana legalization and the number of fatal accidents. So that’s something.

“What is clear from both studies is that marijuana legalization has not resulted in the immediate doomsday scenario that was predicted,” said Mason Tvert of the Marijuana Policy Project.

Could Drivers Challenge the Law?

Even if drivers are over the limit, they might be able to defend the DUI in court. In January 2017, a Colorado regular smoker successfully argued that he was not driving impaired, despite having more than 5ng/ml of THC in his bloodstream. The case was dismissed within an hour.

He was the second person to “beat” the system and we’re going to see more challenges as regular smokers could easily fail a test who could, theoretically, be fit to drive. One survey even found that people are safer drivers when they’ve used marijuana.

The DUI was pure and simple. Now it’s a complex and murky field of law enforcement that is only going to get more confusing. 

Read more about other commonly abused drugs and their health effects, which could impair driving, at