Adding finger-to-nose test improved detection of cannabis-impaired drivers from 67% to 88%
Adding the Finger-to-Nose test and head movement observations to the standard field sobriety test increased detection of cannabis-impaired participants from 67% to 88% at a mean THC of 6.34 ng/mL.
Quick Facts
What This Study Found
Twenty minutes after vaping cannabis (mean THC 6.34 ng/mL), 67% met SFST criteria for suspected impairment. Adding the Finger-to-Nose test plus head movement/jerk observations increased detection by 33%, improving sensitivity from 0.67 to 0.88.
Key Numbers
Mean THC: 6.34 ng/mL at 20 minutes post-vaping. SFST alone: 67% detected. SFST + FTN + HMJ: 88% detected. Sensitivity improved from 0.67 to 0.88 (33% increase).
How They Did This
Observational study where participants used their own cannabis at a research facility. SFST plus supplementary tests administered by certified Drug Recognition Experts at baseline and four times during 150 minutes post-use. Physiological indicators, vital signs, and digit-symbol substitution also assessed.
Why This Research Matters
The standard field sobriety test was designed for alcohol and misses a third of cannabis-impaired individuals. Enhancing the test could significantly improve road safety without requiring blood tests.
The Bigger Picture
As cannabis legalization spreads, law enforcement needs practical, roadside tools to detect cannabis impairment. Unlike alcohol breathalyzers, there is no quick cannabis impairment test. Enhancing existing field sobriety assessments is a pragmatic approach while technology develops.
What This Study Doesn't Tell Us
Participants knew they were being tested (no blinding). Assessors knew participants had used cannabis. Observational design in a controlled setting, not actual roadside conditions. Small sample. Voluntary cannabis use, not dose-controlled.
Questions This Raises
- ?Would these results replicate in blinded, randomized trials?
- ?How does the enhanced SFST perform at lower THC levels or with edibles?
- ?What is the false-positive rate in sober individuals?
Trust & Context
- Key Stat:
- Sensitivity improved from 0.67 to 0.88
- Evidence Grade:
- Observational study with non-blinded assessors provides preliminary evidence but needs validation in randomized and field settings.
- Study Age:
- 2024 observational study of enhanced field sobriety testing for cannabis
- Original Title:
- Enhancing the Standardized Field Sobriety Test to detect cannabis impairment: An observational study.
- Published In:
- Traffic injury prevention, 25(1), 1-7 (2024)
- Authors:
- Beirness, Douglas J(4), Smith, D'Arcy, Brubacher, Jeff R
- Database ID:
- RTHC-05129
Evidence Hierarchy
Frequently Asked Questions
Can police detect cannabis impairment without a blood test?
The standard field sobriety test detected 67% of cannabis-impaired participants. Adding a Finger-to-Nose test and observing head movements improved detection to 88%, offering a practical roadside enhancement.
Why is detecting cannabis impairment harder than alcohol?
The SFST was designed for alcohol, which causes different impairment patterns. Cannabis affects coordination, timing, and attention differently. There is also no cannabis equivalent of a breathalyzer for quick roadside measurement.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-05129APA
Beirness, Douglas J; Smith, D'Arcy; Brubacher, Jeff R. (2024). Enhancing the Standardized Field Sobriety Test to detect cannabis impairment: An observational study.. Traffic injury prevention, 25(1), 1-7. https://doi.org/10.1080/15389588.2023.2262658
MLA
Beirness, Douglas J, et al. "Enhancing the Standardized Field Sobriety Test to detect cannabis impairment: An observational study.." Traffic injury prevention, 2024. https://doi.org/10.1080/15389588.2023.2262658
RethinkTHC
RethinkTHC Research Database. "Enhancing the Standardized Field Sobriety Test to detect can..." RTHC-05129. Retrieved from https://rethinkthc.com/research/beirness-2024-enhancing-the-standardized-field
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.