Raising a successful marijuana intoxication defense against an alleged work-related injury may have been complicated by recent legislation, but defendants can still make it a successful defense if they remember the finer points of proving proximate cause.

Donald R. Barthel

Recreational use of marijuana in California became legal for adults 21 and older on Nov. 9, 2016, when Proposition 64 (Adult Use of Marijuana Act) was approved by voters.

Even though recreational and medicinal marijuana use is legal under California state law, it remains illegal under federal law.

When raising an intoxication defense against an alleged work-related injury, the applicable statute, LC 3600(a)(4), specifically references the “unlawful use of a controlled substance.” This clearly applies to marijuana.

Courts have had to grapple with how to apply the “unlawful use” language to marijuana. In practice, the focus tends to remain on the employer’s ability to prove the two core elements: intoxication and proximate cause.

The legality of recreational and medical marijuana in California does not invalidate an otherwise successful intoxication defense. Because marijuana remains illegal under federal law, California courts have affirmed that employers may still terminate or discipline employees (and successfully defend a WC claim) for using marijuana in violation of a drug-free workplace policy.

The following are key points in an intoxication defense:

Burden of proof is on the defense

Defendants must prove two critical elements by a preponderance of the evidence:

• Employee was intoxicated at the time of the injury.
• Intoxication was the “proximate cause” of the injury.

Difficulty of proving marijuana intoxication

A positive THC test is generally not enough on its own to prove intoxication or impairment at the time of injury, especially with marijuana.

Here are some reasons why:

• THC lingers. Unlike alcohol, THC (the psychoactive component of pot) can remain detectable days or weeks after intoxicating effects have worn off. A positive test proves only past use, not impairment at the time of the accident.
• Need for corroborating evidence. To prove actual intoxication, the defense typically needs to provide additional evidence, such as:
  • Witness testimony regarding the employee’s behavior (slurred speech, poor coordination, impaired judgment) just before the injury.
  • Medical evidence from an expert, such as a toxicologist, demonstrating that the level of THC would have caused psychomotor impairment or significantly affected the employee’s judgment at the time of the injury.

Impacts of AB 2188 on proving proximate causation

Proving that the marijuana use was the proximate cause of the work-related injury is an essential part of an intoxication defense. However, this was complicated by Assembly Bill 2188, which took effect on Jan. 1, 2024.

Though not a court decision, AB 2188 will strongly influence future Workers' Compensation Appeals Board cases:

• Effect. It generally prohibits employers from discriminating against an employee based on a drug test that detects non-psychoactive cannabis metabolites (the inert byproduct of past use).
• Implications for workers’ compensation: If the defense cannot use a standard urine drug screen to justify termination due to off-duty use, it further weakens the already tenuous argument that a positive urine test alone proves active intoxication and causation for workers’ compensation.

Defendant’s focus will now be forced to rely on more costly and difficult-to-obtain evidence, like:

• Testing for active THC (often via blood or oral fluid).
• Extensive witness statements detailing visible impairment (stumbling, slurred speech, confusion).
• Toxicology experts, to connect the THC level to the injury.

Proving proximate causation

Although the intoxication defense is difficult to successfully employ, here are some fact patterns with a “high” (pun intended) likelihood of success:

• Example 1: Construction worker falls from a low wall while walking across a jobsite. Witnesses testify employee was staggering, smelled of marijuana and was “acting confused” just prior to the fall. A high level of active THC (parent compound in a post-accident blood test), combined with witness testimony, will likely be found to demonstrate that intoxication was the proximate cause of the fall.
• Example 2: Employee’s postinjury actions confirm an effort to hide impairment. After a slip and fall, employee refuses immediate emergency medical care on-site, stating that he doesn’t want to be drug tested because he smoked marijuana that morning. This admission (an exception to the hearsay rule), corroborated by the circumstances of the injury (a simple slip on flat ground), is evidence linking the self-admitted intoxication to the cause of the injury.

Takeaways

Have a positive marijuana test? It, like any other intoxication defense, is difficult to prove without scientific evidence and testimony, some of which hopefully comes from a toxicologist or other medical expert.

Don’t forget to:

• Prove intoxication.
• Prove proximate cause.
• Pass the chips (munchies, anyone?).

Don R. Barthel is a founding partner of Bradford and Barthel and is based in the firm’s Sacramento office. This entry from Bradford & Barthel's blog appears with permission.