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Enhancing the SFST to Detect Cannabis Impairment

Author(s): Beirness, Porath, Smith, Beasley

Slidedeck Presentation Only:

3A_Beirness

Abstract:

Background/Context: The Standardized Field Sobriety Test (SFST) was developed to driver assess alcohol impairment and has been shown to have an accuracy of 91% in the detection of drivers with a blood alcohol concentration (BAC) of at least 80 mg/dL. Although often used to assess drivers suspected of drug impairment, the SFST has never been validated as a test of drug impairment. In fact, the sensitivity of the SFST in identifying drivers impaired by cannabis is considerably lower than its sensitivity in detecting alcohol impairment. Research shows that almost 60% of drivers impaired by cannabis will be missed by the existing SFST battery. As more jurisdictions move towards legalized cannabis, there is a need to find a simple means to quickly and easily assess impairment due to cannabis.

Aims/Objectives: The present study sought to find a simple, easy to administer test to supplement the SFST and enhance its ability to detect impairment by cannabis.

Methods/Targets: A database of over 5000 evaluations conducted by Drug Recognition Experts was used to examine the performance on other tests conducted on persons who had used drugs. Scores on the three component tests that comprise the SFST were combined with scores on other tests (e.g., Finger to Nose (FTN), Romberg Balance) to predict cannabis impairment. Measure of sensitivity and specificity were calculated to assess test performance.

Results/Activities: Adding the number of misses on the FTN test and the presence of eyelid tremors to scores on the SFST increased the sensitivity in detecting cannabis from 41% to 85%.

Discussion/Deliverables: Further efforts to enhance the value of the FTN test as a supplemental indicator of cannabis impairment requires the development of a standardized scoring system. Validation studies are also required to provide the evidence required for the FTN to supplement the SFST as a reliable index of cannabis impairment.

Conclusions: The value of the SFST in detecting drug impairment can be improved considerably by adding the FTN test to the protocol. The FTN test is already part of the Drug Evaluation and Classification program and could be easily adapted and incorporated into an enhanced SFST to improve the ability of police officers to detect drug impairment at roadside.