From the Guidelines
The process for issuing a THC DUI citation typically begins when law enforcement officers observe signs of impaired driving and initiate a traffic stop. Officers first look for behavioral indicators of impairment such as erratic driving, weaving between lanes, or delayed reactions at traffic signals. Upon contact with the driver, they assess for physical signs of marijuana use including bloodshot eyes, the odor of cannabis, slurred speech, or poor coordination. If impairment is suspected, officers conduct standardized field sobriety tests (SFSTs) such as the walk-and-turn, one-leg stand, or horizontal gaze nystagmus tests. Some jurisdictions also employ specially trained Drug Recognition Experts (DREs) who conduct more detailed evaluations. Chemical testing may then be performed, either through blood tests, oral fluid tests, or in some areas, breath tests designed to detect THC. The legal threshold for THC impairment varies by jurisdiction, with some states using per se limits (specific nanogram levels in blood) while others rely on evidence of actual impairment regardless of THC concentration. If sufficient evidence exists, officers issue a citation for driving under the influence of THC, which typically includes confiscation of the driver's license, potential vehicle impoundment, and a court summons. This process aims to identify drivers whose cognitive and motor skills are compromised by THC, as marijuana can significantly impair reaction time, judgment, and coordination, making driving dangerous, as noted in studies such as 1. Key factors in determining THC DUI include the presence of THC in the driver's system, observed impairment, and the results of field sobriety tests, highlighting the importance of public health information campaigns related to driving under the influence of cannabis, as discussed in 1. Moreover, the National Highway Traffic Safety Administration has called for research into the development of an impairment standard for driving under the influence of cannabis, as mentioned in 1, emphasizing the need for evidence-based approaches to addressing THC-related impaired driving. Overall, the process for issuing a THC DUI citation is designed to protect public safety by identifying and removing impaired drivers from the road, as supported by the findings in 1 and 1.
From the Research
THC DUI Process
The process for issuing a tetrahydrocannabinol (THC) driving under the influence (DUI) citation involves several steps, including:
- Observation of driver behavior by law enforcement officers
- Administration of field sobriety tests, such as the one leg stand, walk and turn, and finger to nose tests 2
- Collection of blood or saliva samples for THC testing
- Analysis of blood or saliva samples using techniques such as gas chromatography-mass spectrometry or electrochemical biosensors 3, 4
- Determination of THC concentrations in the blood or saliva, with consideration of factors such as the time of sample collection and individual variability in THC metabolism 5, 4
Factors Considered in THC DUI Cases
In determining whether a driver is impaired by THC, several factors are considered, including:
- Blood THC concentrations, with higher concentrations generally indicating greater impairment 5, 2
- Presence of other drugs or substances that may interact with THC or contribute to impairment 6
- Driver behavior and performance on field sobriety tests, such as swaying, stumbling, or difficulty with coordination and balance 2
- Time of sample collection, with earlier collection times generally providing more accurate estimates of THC concentrations at the time of driving 4
Challenges in THC DUI Cases
There are several challenges in THC DUI cases, including:
- Variability in individual responses to THC, with some people experiencing greater impairment than others at the same blood THC concentration 5, 4
- Lack of a widely accepted threshold for THC impairment, with different jurisdictions using different criteria to determine impairment 5, 2
- Limited understanding of the effects of THC on driving performance, particularly at low to moderate blood THC concentrations 6, 4