For just a moment, forget about whether a drug is legal or illegal, prescribed medication or recreational substance. Any drug can impair a person enough to qualify for a Driving While Ability Impaired by a Single Drug (DWAI) charge, in New York, but the process for proving a DWAI is not nearly as straightforward as it is for a Driving While Under The Influence of Alcohol (DWI) charge.

Marijuana intoxication, for example, is wildly inconsistent from person to person. But when a drug’s effects cannot be systematically tracked for all people, then no one can develop a “minimum level” similar to blood alcohol content (BAC). Without a standard, the determination of “impairment” falls to police officers.

Why are drug intoxication levels inconsistent?

According to the CDC, the effects of marijuana vary among individuals based on many factors, including:

• Sex
• Family history
• Medical history

And even so, standard elements such as bodyweight don’t necessarily mean anything in this context. Logically, a very large person’s impairment level should be lower than a smaller person with a similar amount of THC in their system, but in practice, that is not necessarily the case.

This same principle largely applies to most illicit and prescription drugs. Science can tell us that they are present, but whether that presence has led to a more significant impairment than distractions from text messages or alcohol is unknown.

How would police determine intoxication then?

Police in a traffic stop would use the same methods they always use in determining intoxication: observation coupled with the standard field sobriety test. This method is flawed in that it finds its basis primarily in the officer’s opinion. If an officer believes that a person is too intoxicated to drive and under the influence of a drug, then even passing a field sobriety test may not end the police encounter. Most likely, that theoretical person gets arrested, charged with DWAI and faces fines, jail time and license suspension.

But is that fair?

That is the question, isn’t it? Is a process where one person’s opinion, regardless of evidence, can strip another person of their freedom, money and driving privileges fair? This is why defense attorneys exist. Until the law has filled the gap between opinion and science, anyone charged with a DWAI deserves a vigorous, aggressive defense.