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How Reliable is the Observed Impairment Method for Determining Marijuana Use?

Man vaping in car

The recreational use of marijuana is legal in California. California also legalized medical marijuana. However, driving under the influence of marijuana is a criminal offense if the marijuana impairs your ability to drive. 

Unlike alcohol, there is not a “per se” or legal limit for DUI of marijuana. Furthermore, sources disagree about the level of marijuana necessary to impair driving ability. Therefore, a key piece of evidence used in marijuana DUI cases is a police officer’s observation of a driver’s impairment. However, cases of DUI of marijuana based solely on observations of impairment may not stand up in court when challenged by a skilled California DUI defense attorney. 

What is the Observed Impairment Method for Determining Marijuana Use?

Since California does not set a legal limit for the amount of THC (delta-9-tetrahydrocannabinol) in a driver’s bloodstream, a chemical test alone is not generally sufficient to convict someone of driving under the influence of marijuana. Instead, you need evidence that the marijuana impaired the person’s ability to drive.

Many prosecutors use other evidence of driving under the influence of marijuana to obtain a DUID conviction. The evidence is based on observations of impairment by police officers and Drug Recognition Experts (DREs). DREs are police officers trained to recognize the signs of drug impairment in drivers.

Physical symptoms of drug impairment may include:

  • Rapid heart rate
  • Dilated pupils
  • Red eyes
  • The odor of marijuana on the person’s body
  • Rapid breathing
  • Slowed reaction time
  • Dry mouth (“cotton” mouth)

Additionally, police officers observe the driver’s performance on Field Sobriety Tests (FSTs) and the driving patterns immediately before a DUI stop. A driver’s statements to the police and the presence of drug paraphernalia are also observations police officers use to determine drug impairment.

Prosecutors use the combined observations of the police officers or DREs to argue that the driver’s ability to operate the motor vehicle safely was impaired. Therefore, they are guilty of DUID of marijuana.

Problems With the Observed Impairment Method

The observed impairment method has several problems. Studies have shown that marijuana use can affect several driving-related skills. Marijuana use can slow reaction time, decrease divided attention, and cause problems with road tracking. 

However, after reviewing the research on the effects of marijuana use on driving, the NHTSA concluded that there are currently no evidence-based methods to detect marijuana-impaired driving. Many of the “signs of impairment” could be caused by other drugs, alcohol, distraction, illness, drowsiness, and other conditions and driver activities. 

Therefore, it is not possible to know whether police officers could use a unique combination of cues to determine marijuana-impaired driving with any high degree of accuracy. The information was provided in a Report to Congress in July 2017.

Research supported by the National Institute of Justice found that biofluid levels of THC did not correlate with performance on field sobriety tests. In addition, researchers observed standardized FSTs were not effective in detecting marijuana intoxication.

Using observations to detect marijuana-impaired driving can be highly subjective. Someone charged with DUID of marijuana based solely on the observations made by police officers during a DUI stop should fight the charges with the help of a California DUI defense lawyer.

New Methods of Detecting Marijuana Impairment for Drivers

According to studies conducted by researchers at Massachusetts General Hospital, a noninvasive brain imagining procedure is a reliable method for identifying marijuana impairment. Brain activation patterns that correlate to impairment from THC are measured by imaging technology. The technology used is known as functional near-infrared spectroscopy (fNIRS).

The study did not include roadside assessments of impaired driving. However, it did cite the advantages of a portable brain imaging device using this technology to determine marijuana impairment. 

The lead author stated that they believe brain-based testing could provide an objective and practical solution to testing for marijuana-impaired driving. However, further study is required.

Do I Have to Take a Chemical Test if I Am Stopped for DUID of Marijuana? 

California’s implied consent law means that drivers are presumed to have consented to a chemical test for drugs and alcohol if they are arrested for DUI. However, drivers are not required to submit to pre-arrest chemical tests. You can refuse a hand-held breathalyzer test or saliva swab before you are arrested without penalty.

However, after a DUI arrest, refusing to take a chemical test results in an automatic one-year driver’s license suspension, even if the prosecution drops the DUI charges or the court finds you not guilty. In addition, if you are convicted of DUI, refusal of a chemical test adds an extra two days in jail and nine months of DUI school to your sentence. 

Chemical Tests Are Unreliable for Detecting Marijuana Impairment 

There are several problems with chemical tests for marijuana impairment. First, chemical tests do not indicate with any reliability when the driver used marijuana. Second, the tests do not tell officers how much marijuana the person used. Third, experts do not agree on how much marijuana is necessary to impair driving ability.

Another problem is that test results may vary depending on the test used. Blood tests are the most common chemical test used for DUID of marijuana. A blood test indicates the presence of THC in a person’s system. 

Some studies found THC may be detected in a blood test for up to a month after a person uses marijuana. Urine tests can detect the presence of marijuana in a person’s system for up to ten days for a casual user. However, people that use marijuana frequently can have a positive urine test for up to four weeks or longer. 

Saliva tests have not been ruled admissible as evidence in cases of driving under the influence. Therefore, police officers use saliva tests as preliminary screening. But, again, you do not have to agree to take any drug test before you are arrested for DUID in California.

It is important to remember that a positive chemical test shows that you have marijuana in your system. It does not indicate when you used marijuana or how much marijuana you consumed. It also does not prove that you were impaired.

Contact a California DUI defense lawyer to discuss potential defenses to DUI of marijuana. In addition to challenging whether the marijuana in your system impaired your driving, there could be other defenses to driving under the influence of marijuana.

What Are the Penalties for DUI of Marijuana?

California Vehicle Code §23152(f) states it is unlawful for anyone under the influence of any drug to drive a vehicle. Therefore, a person violates this law by:

  • Being under the influence of any drug, including marijuana
  • While driving a vehicle
  • And being unable to operate the vehicle with the ordinary care of a sober person because the drug impairs their mental and/or physical abilities

Medical marijuana is not a defense against DUI of marijuana. Therefore, you may have a prescription for medical marijuana, but you can still be arrested and convicted of driving under the influence of marijuana.

The penalties for DUID of marijuana are the same as DUI for alcohol. Most DUI marijuana cases are charged as misdemeanors. However, it is a wobbler offense. 

Wobbler offenses may be charged as felonies or misdemeanors. For example, if you cause an accident while driving under the influence of marijuana, the prosecutor may charge you with felony DUID of marijuana.

The penalties for a misdemeanor DUI of marijuana generally include:

  • A fine of $390 to $1,000
  • Six months driver’s license suspension
  • Three to five years of informal probation
  • Up to six months in county jail

DUI of marijuana is a priorable offense. Therefore, the penalties increase with each DUI conviction within ten years.

The prosecutor may charge you with felony DUID of marijuana if:

  • You injured someone while driving under the influence of marijuana
  • You have three or more wet reckless or DUI convictions within ten years
  • You have any felony convictions within ten years

The punishment for a felony DUID of marijuana can include substantial prison sentences, formal probation, and longer driver’s license suspension periods. 

What Should You Do if You Are Arrested for DUI of Marijuana in California?

Do not plead guilty to the charges without talking to a California DUI defense lawyer. It is possible to beat charges of driving under the influence of marijuana. You want to avoid a DUI conviction on your driving record if possible.

A DUID of marijuana on your criminal record could have serious consequences. If your employer requires you to drive for employment, you could lose your job. Potential employers may look unfavorably upon past DUI convictions. A criminal record could affect your ability to obtain scholarships and some government aid.

If there is no way to avoid a conviction for DUID, your DUI defense lawyer negotiates the best possible plea agreement for your case. Chemical tests do not show impairment. The observed impairment method for determining marijuana impairment is also subject to challenge.

A skilled attorney uses this information to challenge the prosecution’s case. The prosecutor may be more willing to negotiate a favorable plea deal when they know you have an experienced, knowledgeable California DUI defense attorney ready to argue these defenses in court. 

The post How Reliable is the Observed Impairment Method for Determining Marijuana Use? appeared first on Law Offices of Taylor and Taylor - DUI Central.

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