Company Insights

Protecting Drivers from Misleading Data


Protecting Drivers from Misleading Data Resulting from Current Methods of Cannabis Testing

Breath Testing Is More Accurate and Also Reduces Wrongful Arrests


September 2016 – Safe roads require the right test for cannabis intoxication. The National Highway Traffic Safety Administration (NHTSA) has determined that smoking cannabis less than three hours prior to operating a motor vehicle impairs judgment and compromises driving performance. Robust, reproducible, reliable, and readily available results that measure recent cannabis intake are the foundation of any detection program. There are many possible detection methods for cannabis use, including those based on blood, urine, and – more recently – oral fluid (saliva). However, all of these detection methods suffer from the same pitfall: they can detect THC and its metabolites many days or even weeks after the last cannabis intake, making it difficult, if not impossible, to determine recent cannabis intake accurately.


Some device manufacturers have advocated oral fluid analysis as a roadside test, but the scientific literature shows that this method can still find high levels of THC in recent users 10 hours after use. Thus, people tested via oral fluid analysis could test positive for cannabis even if they have not engaged in the near-term (<3 hour) cannabis use considered dangerous by the NHTSA. This inability to determine recent use accurately leads to the potential for oral fluid testing to implicate many innocent drivers by mistake. In contrast, the scientific literature shows that breath analysis provides results that reliably detect near-term (<3 hours) cannabis intake. This approach works because THC and its metabolites only stay in breath for 2-3 hours, much shorter than blood, urine, and oral fluids, thus more accurately reflecting recent impairment and preventing false positives that could lead to wrongful arrests.


David N. Cornfield, MD

Stanford University

Board of Advisors – Hound Labs, Inc.

Download PDF