Part 3: Cannabis and Driving - Empirical Evidence and Case Law

The relationship between cannabis use and driving safety remains a subject of debate. While there is evidence that 

cannabis can impair driving, it is far less conclusive than alcohol-related impairment.

Empirical Evidence:

- Moderate Risk Increase: Studies show cannabis can impair reaction time and coordination.

- Comparison to Alcohol: Cannabis effects are subtler and depend on individual tolerance.

- Real-World Data: States with legal cannabis show mixed results on crash rates.

Case Law:

- People v. Zuniga (2016): Smell of cannabis alone does not constitute probable cause for DUI arrest.

- Commonwealth v. Davis (2022): Charges against a medical cannabis user dismissed due to unreliable field sobriety tests.

- State v. Gerhardt (2017): Massachusetts Supreme Court calls for more scientifically valid methods.

Policy and Technological Challenges:

- Current methods fail to provide consistent results for cannabis impairment.

- Subjective evaluations disproportionately affect certain groups.

- THC breathalyzers hold promise for more accurate testing.

Conclusion:

This three-part series highlights the challenges in detecting and addressing cannabis impairment in drivers. While 

tests like FSTs, saliva swabs, and blood analysis provide some insights, they are often unreliable and open to bias. 

Case law underscores the importance of observable impairment over mere THC presence, emphasizing the need for better testing methods.