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Marijuana Behind the Wheel.

FEDERAL LAW PROVIDES a system of classifying both prescription and recreational drugs based on their harm to users and harm to society. (1) The ultimate purpose of this drug classification system is public safety. The Controlled Substances Act (CSA) defines a Schedule 1 drug as one that has a high potential for abuse, has no currently accepted medical use in treatment in the United States, and lacks accepted safety for use under medical supervision. (2) Marijuana is a Schedule 1 drug. (3)

In 2015, over 35,000 people were killed in traffic crashes. (4) Nearly a third of those involved an impaired driver. (5) The National Roadside Survey conducted by the National Highway Traffic Safety Administration (NHTSA) demonstrates the increased use of marijuana by our nation's drivers. In the 2013-2014 roadside survey of weekend nighttime drivers, 8.3 percent had some alcohol in their system and 12.6 tested positive for THC (6)--up 48 percent from the number in 2007. (7) Since a majority of states have legalized marijuana for medical and/or recreational use, (8) marijuana-impaired driving cases will continue to present unique challenges for prosecutors and law enforcement.

Marijuana is the most commonly used illicit substance (9) and has become the most commonly detected non-alcohol substance among drivers in the United States. (10)

Generally, impaired driving statutes allow for prosecution of a person who drives (1) while impaired by alcohol, drugs, or any combination thereof, (2) while having a specified level of alcohol in his or her system, or (3) while having any measurable amount of alcohol or drugs in his or her system (e.g., zero tolerance).

Numerous scientific studies demonstrate the relationship between alcohol and the impairment of driving function supporting these "per se" laws. There are challenges, how "per se" laws.

It is difficult to parse out statistical information about impaired driving prosecutions in which marijuana was the impairing substance or even the broader category of drugs in general. This is largely the result of how impaired driving laws are written. Generally, a prosecutor does not need to "prove" what the impairing substance is, only that it impaired the driver. This can be done with circumstantial evidence as well. For example, a driver who exhibits clues of impairment and is found to have a "bong" in his or her car as well as a bag containing a green leafy substance could be successfully prosecuted for DUI even without any chemical test to prove marijuana in his or her system. To change current laws to add a separate charge for drug-impaired driving generally, or marijuana-impaired driving specifically, for purely statistical reasons would likely complicate prosecutions by requiring proof of the impairing substance. Prosecutors may be able to obtain this information from toxicology labs, but may not collect all data for other reasons (e.g., private laboratory not subject to governmental rules or laws, suspect refusal to submit sample for chemical testing, etc.).

As mentioned, a suspect's refusal to submit to chemical testing presents a significant challenge to data collection. Other limitations on data collection include the availability of resources for officer training to detect the signs and symptoms of drug or marijuana impairment, toxicology testing, and the lack of widely available roadside testing mechanisms for drugs or marijuana. Additionally, if an impaired driving suspect submits to a breath test and the results reveal a level of alcohol above the legal limit, there is frequently no further testing performed for drugs and results in the underreporting of drug or marijuana-impaired cases.

While marijuana use has been shown to impair cognitive or executive function, driving performance, and increase crash risk, scientific studies have not yet demonstrated support for marijuana "per se" levels similar to alcohol in impaired driving legislation. Marijuana contains tetrahydrocannabinol (THC), more specifically Delta 9 THC, which is the psychoactive component of marijuana that causes impairment. Delta 9 THC can only be detected in blood. 73-90 percent of this is eliminated in as little as 45 minutes to approximately an hour and a half."

On the other hand, marijuana metabolites, the byproducts in the blood as a result of the body metabolizing the marijuana, remain in the blood for a much longer period of time. Detection of the metabolites may be the result of marijuana consumption several days or weeks prior to the sample collection and may not scientifically equate to impairment.

Some of the issues surrounding the challenges to studies that would scientifically support a marijuana "per se" level include:

* Varying concentrations of THC in marijuana. Generally, the concentrations used in studies are much lower than what is available in real-life settings. Additionally, concentrations vary depending on the form of marijuana ingested.

* Differences between users of marijuana. A chronic, frequent user may develop tolerance to some effects of marijuana but not all effects, including the impairing effect. The effect of THC consumption on impairment of driving performance may be higher for occasional, recreational users than for frequent users.

* Differences in ingestion of marijuana. Smoked marijuana leads to a different absorption rate and release rate of the psychoactive ingredient than does eating marijuana edibles.

* Combined use of marijuana and alcohol or marijuana and other drugs. Various studies have demonstrated that the combined use is associated with significantly greater cognitive impairment and crash risk than the use of one alone. (12)

In terms of marijuana-impaired driving, legislative change has occurred more quickly than the pace of the scientific research on the issue. (11) This leaves fundamental questions about a standard for determining whether an individual's ability to operate a vehicle safely is impaired by marijuana as well as the means which the individual's present status may be measured.

Some practical items to consider prior to setting a "per se" level for marijuana impairment:

* Lack of scientific research.

There is little scientific research supporting marijuana "per se" levels similar to alcohol. Setting a limit for marijuana is strictly based on public policy and in no way means an individual testing below the level is not impaired at the time of driving.

* Even a low "per se" level will miss significant numbers of impaired drivers. Based on the THC concentration distribution in the larger population data set of arrested drivers and similar observations by other groups, indiscriminate selection of a 5 ng/mL threshold for per se laws virtually guarantees that approximately 70 percent of all cannabis using drivers, whose actions led to them being arrested, will escape prosecution under a 5 ng/mL per se standard. (14)

* Sample collection and toxicology testing. Blood testing is the most effective testing method for marijuana, but is the most invasive and costly. Securing a blood sample requires a search warrant that may add a significant delay in specimen collection. This in turn may inhibit the ability to secure information about marijuana in the blood at the time of driving (and the inference of impairment at driving) because of how quickly marijuana transfers from blood to lipid soluble tissues in body. Further, obtaining a search warrant in a routine impaired driving case takes valuable time from the necessary duties of a law enforcement officer.

* Standardized protocols needed. Standardized testing protocols would need to be developed for each type of sample secured.

* Required additional resources. Dedicated resources would likely be needed to train law enforcement officers in the signs and symptoms of marijuana impairment and how to properly document it and train and certify officers as Drug Recognition Experts (DRE). Most police officers that make traffic stops are not trained to become experts in drug recognition due to the costs involved and the requirement that officers respond to numerous types of crimes on any given shift. One-way is to train officers to detect the signs and symptoms of cannabis use in drivers stopped at roadside. Initial suspicion of cannabis use would lead to a field sobriety test (SFST). This process could be coupled with rapid, on-site oral fluid screening for evidence of drug use. The technology to detect certain drugs (including cannabis) in a specimen of oral fluid quickly at roadside is improving and could be used in a manner comparable to preliminary breath testing devices currently used to test for alcohol. The suspect would then be taken for a complete drug evaluation by a DRE. This approach requires enhancing the complement of DRE officers available to conduct assessments for impairment. (15)

Also, additional resources would likely be needed for new laboratory equipment, training, laboratory technicians, and toxicologists since many state laboratories may not be equipped or prepared to conduct THC blood testing. Funding may also be required for other experts to support the prosecution at trial.

* "Per se" limit for marijuana when combined with alcohol or other drugs. If a "per se" limit is to be established, consider legislative change establishing strict liability for an individual found to have any level of marijuana (THC) in his blood at the time of testing when combined with any level of alcohol or the presence of any other drug. Including "time of testing" language may help minimize the problem created by the quick dissipation ofTHC out of the blood as well as avoid attempts to relate amounts back to the time of driving.


Brian Thiede is the Mecosta County, Michigan Prosecuting Attorney. Kenneth Stecker is a Michigan Traffic Safety Resource Prosecutor. An excerpt of this article is in the National District Attorneys Association April 20, 2011 White Paper captioned "Marijuana Policy: The State and Local Prosecutors' Perspective."

(1) Controlled Substance Act, 21 USC [section]801 et seq.

(2) 21 USC [section]812(b)(l).

(3) 21 USC [section]812(c) Schedule 1 (c)(10).

(4) NHTSA press release, "Traffic fatalities up sharply in 2015," https: // accessed February 23, 2017. See also Traffic Safety Facts: Research Note. 2015 Motor Vehicle Crashes: Overview, DOT HS 812 318, August 2016.

(5) Traffic Safety Facts: Research Note. 2015 Motor Vehicle Crashes: Overview, DOT HS 812 318,August 2016.

(6) THC is Delta 9 Tetrahydrocannabinol and is the psychoactive substance in marijuana.

(7) Traffic Safety Facts: Research Note. Results of the 2013-2014 National Roadside Survey of Alcohol and Drug Use by Drivers, by Amy Berning, Richard Compton, and Kathryn Wochinger, DOT HS 812 118, February 2015.

(8) accessed February 23, 2017.

(9), accessed February 23, 2017

(10) "Establishing legal limits for driving under the influence of marijuana," Injury Epidemiology 1:26, Kristin Wong, Joanne E Brady and Guohua Li (2014).

(11) "Effect of Blood Collection Time on Measured Delta-9-Tetrahydrocannabinol Concentrations: Implications for Driving Interpretation and Drug Policy," Clinical Chemistry 62:2, Rebecca L. Hartman, Marilyn A. Huestis, et al. (2016).

(12) See "Establishing legal limits for driving under the influence of marijuana," Injury Epidemiology 1:26, Kristin Wong, Joanne E Brady and Guohua Li (2014).

(13) "Cognitive and Clinical Neuroimaging Core," Marijuana Investigations for Neuroscientific Discovery, Dr. Staci Gruber,,accessed on February 23, 2017.

(14) AAA "An Evaluation of Data from Drivers Arrested for Driving Under the Influence in Relation to per se Limits for Cannabis," May 2016, p. 25.

(15) Id., at p. 27.
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Author:Thiede, Brian; Stecker, Kenneth
Publication:Prosecutor, Journal of the National District Attorneys Association
Date:Nov 1, 2017
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