Why aren’t cannabis breathalyzers the right solution?
Cannabis legalization is proceeding rapidly, largely as a result of social pressure, high costs associated with prohibition, and clear misclassification by the Federal Government. However, legalization is proceeding despite the lack of a safe pathway to legalization when testing for impairment is considered. As a result, the legalization of cannabis has created new challenges for law enforcement and businesses with workers in positions requiring safety or security.
Several alternatives to confront the challenge of cannabis impairment have been developed by companies and researchers. These include two broad categories of device - those that measure the amount of THC, the impairing molecule in cannabis, in a user’s body, and those devices that seek to directly determine impairment through measuring the physiological symptoms of impairment. In the former category, tests exist that measure the amount of THC in blood, saliva, hair, and urine. Several devices are also seeking to come to market that are seek to measure THC in the breath. While this would be an attractive method of measuring impairment given the familiarity with alcohol breath testing devices, there’s simply no scientific evidence that it’s accurate or valid. Despite many studies that have attempted to find such a correlation, none of them have shown that active cannabis impairment can be measured by determining the amount of THC in the body.
The studies below are examples of those that have evaluated bodily THC content and found no correlation to experienced impairment:
Cannabinoid Markers in Biological Fluids and Tissues: Revealing Intake, Marilyn A. Huestis and Michael L. Smith, 2017, https://www.cell.com/pb-assets/journals/trends/molecular-medicine/TRMOME%201304.pdf
Do Δ9-tetrahydrocannabinol concentrations indicate recent use in chronic cannabis users?, Erin L. Karschner et. al., 2009, https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1360-0443.2009.02705.x
The Uneasy Case for Marijuana as Chemical Impairment Under a ScienceBased Jurisprudence of Dangerousness, Andrea Roth, 2015, https://safeandsmartpolicy.org/wp-content/uploads/2015/02/2.5.15-version-DUI-marijuana.pdf
Should Per Se Limits Be Imposed For Cannabis? Equating Cannabinoid Blood Concentrations with Actual Driver Impairment: Practical Limitations and Concerns, Paul Armentano, 2013, https://norml.org/wp-content/uploads/pdf_files/per_se_limits_for_cannabis.pdf
To understand the basis of the need for the Gaize device, it is important to understand the differences in how THC behaves in the body relative to alcohol. The alcohol impairment testing paradigm has been built on measuring the amount of alcohol in the body to determine impairment. This is an accurate way to test alcohol impairment because alcohol is linearly metabolized and expelled by the body over the course of the window of impairment experienced by the user. Blood alcohol content has therefore been reliably correlated with impairment, which has led to the 0.08% blood alcohol limit that the United States has universally adopted. Blood alcohol levels are easily correlated with breath alcohol levels, which is the basis for breathalyzer devices. Using the linear and predictable nature of alcohol metabolization therefore, it is possible to accurately measure alcohol impairment using blood, and breath testing devices.
Unfortunately, THC from the consumption of cannabis doesn’t behave the same way in the body that alcohol does. Delta-9-Tetrahydrocannabinol (THC), is rapidly expelled by the body or stored in fat. As the chart below shows, it can drop to all but undetectable levels within 30 minutes of smoking, while the experienced high of the user persists for several hours. The amount of THC in the body and the experienced impairment are therefore uncorrelated in the available bodily fluids (blood, saliva, urine), as well as in breath. One can easily contrast the THC curve to the extremely linear one for alcohol and understand this important difference.
Given these characteristics, it’s easy to see why no study has found a correlation between impairment and THC concentrations in the body. The chart below adds the dimension of the subjective high as experienced by users. This line shows a rapid onset, peaking within about 15 minutes, then plateauing before slowly declining starting around 90 minutes.
Breathalyzers can only detect smoked cannabis within a two hour window of use. As is shown by the chart below, and as can be learned through any cannabis experience or by interviewing cannabis users, the experienced high lasts long after this window. A cannabis user is still experiencing significant levels of motor function and reaction time impairment when THC breathalyzers are no longer able to detect the substance.
THC is also lipophilic, or fat soluble. It is stored by fat in the body after use and then slowly released over time. This THC is non-psychoactive, but is still detectable and therefore is problematic for THC tests. In a heavy cannabis user, non-psychoactive THC will be present in levels that could exceed the per se limits for cannabis set by some states, even when the individual is not impaired. That, of course, further confounds efforts to measure impairment by measuring bodily THC content.
Another problem is the differences in metabolism from the various methods of ingesting THC. As the chart below demonstrates, smoked cannabis and oral (ingested/edible) cannabis differs greatly in terms of onset time, duration of subjective high, and metabolite present.
The experienced high from smoked cannabis rises rapidly, while it comes on very slowly for edible cannabis. Both smoked and ingested cannabis users experience a plateau in their experienced high, lasting for several hours. However, whereas smoked cannabis has a remarkable spike in the body immediately after consumption, the THC content in the body from ingested cannabis stays very (almost undetectably) low. Meanwhile, the precipitous drop in THC after smoking is clearly uncorrelated with the high experienced. These differences in detectable THC and experienced impairment totally invalidate the legal utility of per se laws in states that have adopted them. The quote below from a cannabis researcher is illuminating:
“Current research also indicates that biological THC concentrations are not strongly correlated with impair- ment, so per se laws that criminalize driving above spe- cific thresholds do not appear to be justified as stand- alone policy.”
In states where cannabis is legal, it is no longer sufficient to determine the simple presence of THC to determine if a crime has been committed. That is, states must prove beyond a reasonable doubt that a cannabis user was impaired - a challenging burden of proof. Breathalyzers, like bodily fluid tests are therefore not useful tools for law enforcement. Leaders in the space, from researchers, policy advocates, legislators, and even the International Association of Chiefs of Police has been opposed to cannabis breathalyzers for exactly this reason.
Rather than attempt to measure bodily THC content, Gaize determines the experienced impairment of cannabis users though measuring involuntary micromovements of the eye. This is the basis of the existing Standardized Field Sobriety Tests (SFST), which have been repeatedly validated as reliable measurements of impairment in alcohol, cannabis, and some other drugs.
Originally researched and developed from 1975 to 1981 by the National Highway Traffic and Safety Administration (NHTSA), the Standardized Field Sobriety Tests are intended to allow an officer with no tools other than their observations to determine if a subject is impaired. They are based on the scientific understanding of how alcohol, cannabis and other drugs impact a user’s ability to conduct basic tests of balance and dexterity, and importantly, how these substances impact involuntary eye movement. These tests give officers “probable cause” to arrest a vehicle operator for driving while impaired (DWI) or driving under the influence (DUI). Drug Recognition Expert (DRE) officers are the best trained law enforcement officers at determining drug impairment. They go to a special school where they learn to recognize these indicators, among others.
While proven to be reasonably accurate at establishing whether or not a vehicle operator is under the influence of an intoxicating substance (65-85% depending on the study), Drug Recognition Expert officers who conduct Standardized Field Sobriety tests are subject to inescapable opportunities for inaccuracy. Those include: human error in conducting or interpreting tests, subjectivity of interpretation in test results, and a distinct lack of corroborating evidence generated in the process to validate an officer’s determination. Further, there are far too few DRE officers in the United States.
The Gaize product is an automated eye tracking test that utilizes advanced sensors to collect extremely accurate eye movement data throughout the test process. The eye tracking data captured by the device is then immediately evaluated using a proprietary machine learning algorithm to determine real-time impairment. Further, eye video is captured and made available to customers for interpretation by expert witnesses or simply as a record of the eye characteristics at the time of testing.
