Cannabis and impaired driving

Testing for metabolites of THC, versus the actual THC intoxicant, can result in DUID convictions of users who aren't actually impaired.[28] According to National Institute on Drug Abuse, "the role played by marijuana in crashes is often unclear because it can be detected in body fluids for days or even weeks after intoxication".[29]

According to a 2017 Report to Congress produced by the U.S. National Highway Traffic Safety Administration, many of the THC immunoassay screening tests used by law enforcement can give a false positive of THC metabolites. This is because these screenings tests "lack high specificity [and] are subject to cross-reactivity."[6] After this initial screening, it is typical for a more accurate, specific test to be conducted.[6]

In some areas, law enforcement uses on-site kits to collect oral fluid. (It is possible that law enforcement may be required to obtain a search warrant prior to taking this sample.) But it has not yet been shown whether these tests are accurate or reliable, and it is possible a false positive could result from environmental exposure.[6]

It is possible that prior users of chronic cannabis users can test positive for THC even months of years after they have stopped using cannabis; there is evidence that cannabis metabolites can become stored in fat tissue and then be released due to stress or weight loss.[30]

Fat solubility of THC also makes detection in body fluids, which are mostly water, problematic, leading to false indication of non-impairment for users.[28]

Germany's blood serum (not whole blood like most standards) THC-A limit is 1 ng/mL.[32][33]

Driving under the influence of drugs is kind of road safety traffic offense information which can exchanged by member states of the European Union in the scope of directive 2011/82/EU of 25 October 2011.[35]

In Uruguay, the first nation to legalize cannabis, "any THC detectable in the body will deem a motorist impaired to drive".[36] Reporting has indicated that blood tests would be utilized.[37] Canadian draft regulations proposed in 2017 (Bill C-46) had summary conviction offences starting at 2 nanograms per milliliter.[22][38]

Some legal scholarship has argued that per se cannabis-DUID laws violate the Due Process Clause under the Fourteenth Amendment of the Constitution because they "subject drivers to criminal prosecutions without any real culpability."[39]

At the federal level, the United States Department of Transportation regulates public transportation (e.g. pilots, bus drivers, and train operators) and commercial truckers.[40][41] 49 CFR Part 199 and 49 CFR Part 40 set maximum urine concentration levels of THC-A as the threshold for impairment for regulated transportation occupations.[41] As of January 1, 2018, the THC-A testing cutoffs were 50 ng/mL for an initial immunoassay test and 15 ng/mL for a confirmatory gas chromatography–mass spectrometry test.[42]

All fifty states criminalize driving while under the influence of drugs.[43] These state laws fall into three categories: (1) "zero tolerance" laws, which criminalizes driving with any amount of THC and/or its metabolites in the body; (2) "per se" laws, which criminalize driving with a certain level of THC in the body; (3) laws that focus on whether the driver was actually impaired or affected by THC; and (4) "permissible inference" laws, which allow an inference of impairment if the THC blood level is at least 5 ng/ml.[44]

Arizona Revised Statute § 28-1381(A)(3)[45] makes it illegal to drive or be in actual physical control of a vehicle while there is cannabis or its metabolite in the body. The statute was challenged as violating the equal protection clauses of the federal and Arizona constitutions in State v. Hammonds,[46] but the Court of Appeals of Arizona upheld the statute on the grounds that the "presence of an inactive and nonimpairing metabolite of an illicit drug in a driver's urine does not necessarily mean that there is no active component of that drug present in the driver's blood." In a law review article, attorney Joshua Snow argues that the court's reasoning is flawed because "there is no way of knowing when, how, or where the metabolite entered the body,"; thus, "the state cannot prove that an individual was operating a motor vehicle with the active controlled substance in the body."[30]

Medical marijuana patients are not subject to prosecution under § 28-1381(A)(3) unless actual impairment can be shown.[47] In 2010, Arizona passed the Arizona Medical Marijuana Act, § 36-2802,[48] which provides that a "registered qualifying patient shall not be considered to be under the influence of marijuana solely because of the presence of metabolites of components of marijuana that appear in insufficient concentration to cause impairment."

In State ex rel. Montgomery v. Harris (2013),[49] the Supreme Court of Arizona held that § 28-1381 applies only to metabolites capable of causing impairment. In this case, the defendant's blood tested positive for Carboxy-THC, a non-impairing metabolite of cannabis.

California Vehicle Code §23152(f)[50] makes it unlawful for a person under the influence of any drug to drive a vehicle. For a person to be convicted under this statute, the drug or drugs "must have so far affected the nervous system, the brain, or muscles as to impair to an appreciable degree the ability to operate a vehicle in a manner like that of an ordinarily prudent and cautious person in full possession of his faculties."[51] In People v. Torres, the defendant's urine tested positive for methamphetamine, and there was expert testimony that established that methamphetamine could impair a person's "judgment, focus, and psychomotor skills" so as to make driving unsafe; however, there was no evidence that the defendant's methamphetamine use actually impaired his driving ability the night he was arrested.[51] Thus, the California Court of Appeal held there was insufficient evidence to support the defendant's conviction.[51]

Colorado has a "permissive inference" DUI law; Colorado statute § 42-4-1301(6)(a)(IV) provides that if "the driver's blood contained five nanograms or more of delta 9-tetrahydrocannabinol per milliliter in whole blood, as shown by analysis of defendant's blood, such fact gives rise to a permissible inference that the defendant was under the influence of one or more drugs."[52]

Delaware Statute § 4177(a)(2)[53] makes it a crime to drive under the influence of any drug. §4177(a)(6)[53] makes it a crime to drive when the blood contains, within 4 hours of driving "any amount of an illicit or recreational drug that is the result of the unlawful use or consumption of such illicit or recreational drug or any amount of a substance or compound that is the result of the unlawful use or consumption of an illicit or recreational drug prior to or during driving." Subsection 3(a) of §4177 provides that no person shall be convicted under (a)(6) when they did not ingest the drug prior to or during driving but only after they ceased driving—and only that post-driving ingestion caused their blood to contain the drug.[53] Subsection 3(b) provides that no person shall be convicted under (a)(6) when they "consumed the drug or drugs detected according to the directions and terms of a lawfully obtained prescription for such drug or drugs; however, nothing in 3(a) or 3(b) prevent a driver from being prosecuted under § 4177(a)(2).[53]

Georgia Statute § 40-6-391[54] makes it to drive while there is "any amount of marijuana . . . present in the person's blood or urine, or both, including the metabolites and derivatives of each or both . . . ." Subsection (b) of the statute provides that being legally entitled to use a drug is not a defense to the statute if the person is still "rendered incapable of driving safely as a result" of using that drug.[55]

Illinois Vehicle Code 625 § 5/11-501[56] makes it a crime to drive or be in actual physical control of a vehicle while under the influence of any drug "to a degree that renders the person incapable of safely driving," (subsection (a)(3)) or while "there is any amount of a drug, substance, or compound in the person's breath, blood, other bodily substance, or urine resulting from the unlawful use or consumption of a controlled substance listed in the Illinois Controlled Substance Act..." (subsection (a)(6)). 11-501(a)(6) creates a strict liability offense (meaning the State does not need to prove anything regarding mental state)--but it does not create criminal liability for a person who ingests cannabis inadvertently or unknowingly.[57] In People v. Gassman, 622 N.E.2d 845, appeal denied 642 N.E.2d 1291, defendant argued that 11-501(a)(6) violated due process and the equal protection clause, but the Appellate Court of Illinois, Second District, rejected his arguments.[57] In People v. McPeak, a police officer smelled cannabis around defendant, found drug paraphernalia in his car, and defendant admitted to smoking "two hits" of cannabis one hour prior. But the Appellate Court of Illinois, Second District, found that the evidence was insufficient to sustain a conviction because there was no evidence that consuming that amount of cannabis would result in cannabis being left in his breath, blood, or urine one hour later, there was no evidence of odor of cannabis on his breath, and there was no evidence that defendant was impaired.[58]

Indiana Statute 9-30-5-1[59] makes it a crime to drive with cannabis or its metabolite in the body.

Iowa Code section 321J.2(1)(c)[60] criminalizes the operation of a motor vehicle while "any amount of a controlled substance is present" in the driver's blood or urine. In State v. Comried,[61] the Iowa Supreme Court interpreted this statutory language to mean "any amount greater than zero"—even if that amount is nonimpairing. In State v. Childs,[62] the defendant argued that Comried should be overruled because it relied on an Arizona decision[63] that had since been overruled by State ex rel. Montgomery v. Harris, 322 P.3d 160 (2014), which held that the presence of a non-impairing metabolite of cannabis is not sufficient for a DUI conviction. The Iowa Supreme Court, however, declined to adopt the Harris rule and instead reaffirmed Comried.[64]

Section 257.625[65] of the Michigan Vehicle Code criminalizes driving a motor vehicle with "any amount of a controlled substance listed in schedule 1 under section 7212 of the public health code." (Cannabis is listed as a controlled substance.)[66] In People v. Koon, 832 N.W.2d 724, the Supreme Court of Michigan held that drivers who possess a valid Michigan Medical Marijuana Act card are not subject to prosecution under § 257.625 unless the state can show they were "under the influence" while driving.[67][47]

Minnesota Statute § 169A.20 makes it a crime for any person to drive while "under the influence of a controlled substance."[68] According to the standard jury instructions, "There is no set standard as to the quantity of a controlled substance a person must ingest before [they are] regarded as being 'under the influence.' When a person is so affected by a controlled substance that the person does not possess that clearness of intellect and control of [themselves] that [they] otherwise would have, that person is under the influence of a controlled substance. If, as a result of consuming a controlled substance, the person's ability or capacity to [drive] is impaired, the statute has been violated."[69] These standard jury instructions were cited by the Court of Appeals of Minnesota in an unpublished case, State v. Suber, 2008 WL 942622.[70] In Suber, the Court of Appeals of Minnesota overturned the defendant's conviction, finding lack of sufficient evidence. The defendant admitted he had consumed cannabis about 17 hours before his arrest; police testified that defendant performed poorly on field sobriety tests; police testified that defendant's eyes appeared red and watery; and defendant's urine tested positive for cannabis. But the court still held that this evidence was not sufficient because the state's drug recognition expert testified that cannabis could bed detectable in urinalysis for seven to ten days after ingestion, the state did not have any direct proof that the defendant ingested cannabis in the hours leading up to him driving, and there was evidence to support defendant's story of innocence: that his eyes were red and watery due to lack of sleep, and that his performance on field sobriety tests was affected by the fact that he had Asperger's syndrome.[70]

Nevada Revised Statute § 484C.110(4) makes it unlawful to drive with 2 ng/mL of delta-9-tetrahydrocannabinol (cannabis) or 5 ng/mL of 11-OH-tetrahydrocannabinol (cannabis metabolite) present in their blood or urine.

New York's Vehicle and Traffic Law § 1192(4)[71] provides that "[n]o person shall operate a motor vehicle while the person's ability to operate such a motor vehicle is impaired by the use of a drug." Courts apply a four-step process in determining whether there is a prima facie case for a violation of § 1192(4): (1) defendant ingested a drug; (2) the drug is one proscribed by Public Health Law § 3306; (3) defendant drove after ingesting the drug; and (4) while driving, defendant's driving ability was impaired by the drug.[72][73][74] But there is a qualification to this test where the ingested drug is cannabis: there must be a showing of substantial impairment. In People v. Shakemma,[73] a police officer's observation of defendant's car swerving off of the road and onto the road shoulder by half a car width, of the smell of cannabis on her car, and of her red eyes and pinpoint pupils, did not rise to the level of showing substantial impairment.[73] The District Court of New York dismissed state's case for lack of probable cause.[73]

Ohio Statute § 4511.19[75] makes it unlawful to drive with a concentration of cannabis of at least 10 ng/ml in their urine or 2 ng/ml in their blood or blood serum or plasma. If the person is the under the influence of alcohol, a drug of abuse, or a combination of them, then it is unlawful to drive with a concentration of cannabis metabolite of at least 15 ng/ml in their urine, or 5 ng/ml in their blood or blood serum or plasma. It is also unlawful to drive with a concentration of cannabis metabolite of 35 ng/ml in their urine or 50 ng/ml in their blood or blood serum or plasma.

Oklahoma Statute 47 § 11-902 makes it unlawful to drive or be in actual physical control of a vehicle who has any amount of cannabis or one of its metabolites or analogs in their "blood, saliva, urine or any other bodily fluid at the time of a test . . . within two hours after [their] arrest."[76]

Pennsylvania Statute § 3802(d)(1) makes it a crime to drive if there is any amount of cannabis, or cannabis metabolite, in the blood. The statute was constitutionally challenged as violating equal protection in Com v. Etchison, 916 A.2d 1169, appeal granted in part 935 A.2d 1267, affirmed 943 A.2d 262, but the Superior Court of Pennsylvania upheld the statute as constitutional.[77]

Tennessee does not have a per se law for drug impaired driving;[78] rather, Tennessee courts take a totality of the circumstances approach, examining factors such as erratic driving, performance on field sobriety tests, presence of drugs or paraphernalia, and observed behavior such as slurred speech and unsteadiness.[79]

Utah Code Section 41-6a-502 criminalizes driving "under the influence of alcohol, any drug, or the combined influence of alcohol and any drug to a degree that renders the person incapable of safely operating a vehicle."[80] Where a person is not under the influence of cannabis to the extent sufficient to be convicted under this DUI code section, but still has a detectable level of THC in their system, they can still be convicted under section 41-6a-517,[81] which criminalizes driving with "any measurable controlled substance in the body." (THC is listed as a "controlled substance" under Section 58-37-4's.[82]) In a law review article, attorney Joshua Snow has argued that this statute violates the Eighth Amendment to the U.S. Constitution as well as the Utah Constitution's Uniform Operation of Laws Clause.[30]

Revised Code of Washington § 46.61.502[83] provides that a person is guilty of driving under the influence if, within two hours of driving, they have a THC concentration of 5.00 or higher as shown by analysis of their blood. The state legalized cannabis for recreational use in 2014.[84] The research director of the Washington Traffic Safety Commission has called the 5.00-nanogram threshold "completely arbitrary," saying that it "wasn't backed by scientific theories then, and it's not backed by scientific theories now."[85]

Wisconsin Statute § 346.63(1)(am)[86] makes it a crime to drive with "a detectable amount of a restricted controlled substance in his or her blood." (Delta-9-tetahydrocannabinol is a "restricted controlled substance" under Wis. Stat. § 340.01(50m).)[87] § 346.63(1)(d) provides that it is a defense to (1)(am) if defendant proves by a preponderance of the evidence that at the time of the incident they had a valid prescription for delta-9-tetrahydrocannabinol.[88] In State v. Smet, the defendant argued that § 346.63(1)(am) violated due process and the equal protection clause, but the Court of Appeals of Wisconsin rejected his arguments.[89]

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