July-August 2012

10 myths about drugged driving

There are a lot of misconceptions about driving while impaired by drugs. Here are the facts to assist prosecutors in trying these increasingly common cases.

Warren Diepraam

Chief of Vehicular Crimes Division in Montgomery County

Impaired driving prosecution usually involves cases where alcohol is the substance causing impairment. The efforts of victim’s advocacy groups, police, traffic safety agencies, and prosecutors have made a difference in—rightly—bringing attention to alcohol and driving.

    Recently however, drug-impaired driving is—also rightly—receiving more attention from law enforcement agencies. Although this increased focus will ultimately have traffic safety benefits, there are many difficulties in handling these types of cases: Peace officers are generally not familiar with what may be subtle signs of drug impairment; if alcohol is combined with a drug, the focus is often on alcohol; and while blood alcohol quantitations can be related to impairment, drug quantitations (that is, the number of milligrams of drug per milliliter of blood) generally cannot. Because the incidence of drug-impaired driving is increasing, we as prosecutors must combat the most common myths associated with this crime.


The first myth is that hospitals will automatically take a blood sample from a driver if medical personnel or police suspect impairment. In truth, hospitals rarely take blood samples, even though one would think that doctors would want to know what drugs are affecting a person prior to administering treatment. But certain archaic financial reasons (health insurance often won’t pay claims if the patient is intoxicated) may prevent the hospital from taking these steps necessary for investigation and, later, prosecution. The remedy for this issue is to use a search warrant or other legal process to obtain the hospital blood samples and submit them to a forensic lab for testing, keeping in mind that time is of the essence as hospitals destroy their samples in as little as 24 hours.


The second myth is that if a hospital does obtain a sample, it will be checked for drugs. In fact, most hospitals will not test for drugs and if they do, they will search only for a limited class of drugs, such as cocaine, marijuana, phencyclidine, amphetamine, and LSD. This practice creates two problems for law enforcement: The first is that such testing will not detect a significant number of legal and illegal drugs. Secondly, the hospital’s tests are merely screening tests and not confirmatory tests. A screening test involves the use of chemicals that react with certain classes of drugs; the process is similar to the tests officers use to identify drugs on the street. Such screening tests have a fairly high false-positive rate, which is the reason for confirmatory testing with a gas chromatograph. Screening methods are generally reliable and therefore relevant, but the defense lawyer will still have a significant issue to advance in trial. Again, the remedy for this issue is to obtain the blood samples from the hospital, submit them to a forensic lab, and request a full toxicological screening.


Next is the common belief that the presence of drugs in hospital records means the subject is impaired. This notion is faulty for several reasons. Unlike with alcohol, there is little scientific support that equates certain drug dosing levels with impairment. As of now, alcohol is the only drug where such dosing levels can be scientifically supported and admitted in court. The presence of drugs in hospital records does not necessarily mean that the subject is impaired. Further compounding this problem is that hospitals rarely quantify blood-test results and are merely reporting the presence of the drugs. Because Texas law currently has no per se levels for drugged driving, prosecutors must prove impairment when drugs are involved. The driving facts, impressions of medical personnel and paramedics, and medical records may be helpful to prove impairment, but there is no substitute for a police officer trained in drug detection and impairment evaluating the suspect at the hospital.


Although there is little scientific support for quantitation relating to impairment, prosecutors should avoid the myth that dosing levels are not important. When combined with visual indicators of impairment through a trained police officer or other person, quantitation does have significant value because certain levels of a drug or its metabolite, combined with another person’s observations, makes it more likely that the drug is causing the impairment.

    Lastly, quantitation can be used to determine the general time of ingestion (as opposed to the general symptom of impairment), which is helpful to describe what symptoms a person would experience at that point in the metabolic process. Most forensic labs will perform this quantitative analysis, and the few labs that do not conduct it still have the instrumentation to do so.


If a quantitation is obtained, prosecutors then have to deal with the next myth, that an ingested drug in a therapeutic dose does not create impairment. In fact, many drugs taken in therapeutic doses are highly impairing. For example, anybody having surgery will rely on a therapeutic dose of anesthesia so the surgeons can operate. In such a case, the patient will be impaired and unconscious on a therapeutic dose. Although not an exhaustive list, some drugs that are highly impairing at therapeutic doses include LSD, Ambien, and Soma. Any prosecutor handling a drug-impaired driving case must dismantle this myth for the jury and emphasize the physical or mental signs of impairment.


The next myth is that drugged drivers are easy to identify. Highly impaired drugged drivers are obvious to most people, but those who are mildly impaired frequently escape arrest and prosecution. The alcohol equivalent is prosecuting a driver with a low alcohol blood result or a person who fails but does well on field sobriety testing. These individuals may not be “drunk,” but they are obviously a danger on the roads.

    The same principles apply to drug-impaired drivers. It is imperative that officers are trained on recognizing the signs of drug impairment by taking classes such the Drug Recognition Expert (DRE) or Advanced Roadside Impaired Driving Enforcement (ARIDE) courses. Additionally, the TDCAA forensic science project has several tools available to prosecutors and law enforcement to assist in impaired driving detection and apprehension. By being proactive and recognizing drug-impaired drivers, peace officers will arrest more offenders. The fear of apprehension and prosecution will increase as will deterrence.

    Even more myths arise post-arrest. Many suspects will offer a breath sample as an alcohol rule-out. After that, the question becomes what sample to collect: urine or blood?


An old myth is that a urine sample is best. While urine was once the preferred sample, blood is now the sample of choice. Urine is the body’s reservoir for expelled toxins and waste products; as a result, urine tests are less likely to be correlated to an opinion on impairment. Conversely, the amount of a drug in a person’s blood is more reflective of the substance’s effects on the nervous system because the substances are still being processed or metabolized. While blood samples are the general trend in drug cases, urine can still be useful and should not necessarily be discarded.


Once blood is obtained and the sample tested, drugs or their metabolites are sometimes not detected, leading to our next myth: that a negative blood result means the suspect ingested no drugs and the officer was wrong in his assessment of impairment. While that’s definitely a possibility, it is not always the case. There may be many other reasonable explanations for a negative result. For example, labs set cutoff levels on detecting drugs versus reporting drugs, and these levels vary from lab to lab. (A higher cutoff level can save a laboratory significant costs by precluding the need for further confirmations and testing.) If the lab obtains a result but the result is below its reporting level, the lab will send out a negative report. A prosecutor should check with the lab and inquire if there were drugs present that were not reported.

    Even if the test came up negative, many substances are extremely volatile and are metabolized before the blood is taken. Some substances can be quickly destroyed in the blood sample due to volatility, even with the preservative contained in the grey-top tube. In addition, there are literally thousands of intoxicating substances on the market and new ones being developed weekly. Labs are not able to develop protocols for detecting all of these substances. The explosion in designer drugs and synthetics such as salvia, bath salts, and K2 are but a few examples of new arrivals that need new testing protocols.


Another significant myth is that the increasing use of blood samples courtesy of a county’s no-refusal program and recent changes in the laws will minimize the need for the DRE or ARIDE programs. This could not be further from the truth. In states, including Texas, where there is no per se level for drug-impaired drivers, we need officers to testify about the subject’s level of impairment and whether it is consistent with any drugs. Evidence of physical and mental impairment is still necessary and must be proven beyond a reasonable doubt.


A related myth is that if an officer describes a class of drugs different from what the lab results show, the officer’s assessment of impairment is wrong. Again, this is not necessarily true. For example, many drugs can affect people differently and symptoms for one class of drugs may mimic symptoms from another, especially with poly-substance abusers. Additionally, some substances may not have been detected due to cutoff levels or lack of testing, even when they were present at the time of the DRE evaluation. Lastly, some drugs have a certain class of physical manifestations in one phase and another class in a different phase. For example, a person under the influence of a stimulant may show symptoms of a depressant when in the downside, or crash phase, of stimulant use. All these factors and more should be considered when the officer and the lab results conflict.

    In conclusion, the new focus on drug-impaired driving will require prosecutors to become more knowledgeable about the process of obtaining blood evidence, interpretation of lab analysis, and effects that different types of drugs can have on the human body. We have an ethical obligation to become familiar with these issues. Through increased awareness and focus on drugged driving and the myths associated with this crime, we can do a better job of making our roadways safer by ensuring that those in need of prosecution face the consequences of their actions and those that don’t are released from the system.