Drug Based DWI Cases

By Collin County Criminal Defense Lawyer Jeremy Rosenthal

(972) 369-0577


What happens when someone gets arrested for Driving While Intoxicated but there is little or no alcohol detected?

The Legal Basis for DWI Arrests Without Alcohol Involved

Chapter 49 of the Texas Penal Code defines driving while Intoxicated as operating a motor vehicle in a public place while intoxicated.  Intoxication is further defined by Tex.Pen.C. 49.01.  Under that chapter “Intoxicated” means:

(A) not having the normal use of mental or physical faculties by reason of the introduction of alcohol, a controlled substance, a drug, a dangerous drug, a combination of two or more of those substances, or any other substance into the body; or (B) having an alcohol concentration of 0.08 or more.

So as you can see Texas recognizes a laundry list of things which could cause intoxication capped by the catch-all phrase “any other substance into the body.”  Taken literally this could mean sugar, coffee, or even water if it caused you to “not have the normal use of your mental or physical faculties.”

The Major Difference Between Drugs and Alcohol For DWI Arrests

There is a “per-se” definition of intoxication for alcohol but none for “street drugs” such as marijuana, cocaine, or even heroine… nor is there a per-se definition of intoxication for prescription medications such as hydrocodone, oxycontin, or xanax.

This is to say the scientific community agrees no one is safe to drive at 0.08 or higher BAC.  In other words, at 0.08, everyone is intoxicated.  There is no similar number or level for drugs.

Even the State’s most loyal toxicologists cannot say for certain that at any given amount of marijuana, for example, caused a specific person to be intoxicated on a specific occasion.  They may testify such a drug “affected” the driver but any lawyer’s ears should ring when they hear those words — because those probably aren’t legally sufficient to sustain a conviction for driving while intoxicated.

The Real Battle

Drug based DWI cases can be real dog-fights in the courtroom.  This is because it is at the intersection of science and bias.

Pharmacologists, toxicologists and people of science will tell you up and down just how difficult (if not impossible) it can be to tell whether a person has lost the normal use or about what caused a person not to have the normal use of mental or physical faculties based on drugs… but this doesn’t stop police officers, prosecutors, or jurors from from making knee-jerk reactions based on some of the drugs involved or based on the behavior they observe.

Prosecutors know many juries will convict a person for almost anything when they hear a person used marijuana or xanax.  This doesn’t make it legal.

In many cases police who may have had some training in the detection of drug impairment will attempt to testify as if they are a qualified physician able to diagnose highly complex situations of drug ingestion.  Also many officers claim to learn about the effects of drugs on the job through their “training and experience.”  This can often be a concocted phrase that makes them experts on everything from hydrocodone to tennis racquets to waffle irons.  They mean well but I’m pretty sure they’d get a 2nd opinion if a fellow officer diagnosed one of their loved ones with a life-altering disease (which a DWI diagnosis can be).

How Courts Struggle With Drug Related DWI Arrests

Courts are the ‘gatekeepers’ of evidence which juries receive to come to their verdicts.  The law school example is the Judge should exclude testimony from a witness who claims the moon is made of cheese.  In drug based DWI arrests, then, the issue is whether a judge should even allow a police officer with several hours of training (if any) on pharmacology or toxicology to speak as if they have post-graduate degree on the matter.

In Layton v. State, 280 S.W.3d 235 (Tex.Crim.App. 2009), the Court of Criminal Appeals ruled use of medications was not admissible in a case where alcohol was the main intoxicant unless the State could show the dosage of the medication taken, the time of ingestion and the half-life of the drug.  But, as always, Courts are constantly re-analyzing the edges of the issues and often reaching contrary conclusions.

What You Need to Do if You’re Charged with a Drug Based DWI

Don’t assume you’ll lose or that things are hopeless.  These cases can be real battles but they are highly complex and many are winnable.  Call an experienced lawyer.

*Jeremy Rosenthal is Board Certified in Criminal Law by the Texas Board of Legal Specialization and licensed by the Supreme Court of Texas. Nothing in this article is intended to be legal advice.  For legal advice about any situation you should contact an attorney directly.  Contact through this forum is not privileged nor confidential.


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