Mouth Swab Tests in California DUI Cases

A mouth swab test (“MST”) is used by law enforcement personnel to check whether drugs are in a driver's system. The test is used in the field once an officer suspects that a driver is driving under the influence of drugs (DUID).

Drivers can refuse to take the test. If they do, they can still get arrested for DUID if the officer has probable cause that the driver is high.

The MST is used because other roadside tests -- such as a breathalyzer test or a blood test -- either do not detect the presence of drugs or are inefficient in doing so.

The mouth swab test can detect seven specific drugs (including marijuana and cocaine). However, it cannot detect the precise level of drugs in a person's system. Blood tests are used to determine this. A driver can face penalties if he refuses a blood test or other chemical tests.

A positive mouth swab test typically results in the driver getting arrested for DUID. He must submit to a blood test. A negative test can still result in an arrest if an officer suspects the driver is high,

Unlike driving under the influence of alcohol (DUI) cases, there is no “legal limit” for drugs and driving.

A California DUID can be charged either as a misdemeanor or a California felony. The crime is punishable by:

  • jail time,
  • fines, and/or
  • license suspension.

Our California DUI defense attorneys will highlight the following in this article:

mouth swab dui
A mouth swab test (“MST”) is used by law enforcement personnel to check whether drugs are in a driver's system

1. What is a mouth swab test?

A mouth swab test is used by law enforcement personnel to check whether drugs are in a driver's system. The test is used in the field once an officer suspects that a driver is under the influence of drugs.

The name of the MST device is the Drager Drug Test 5000. The machine is about the size of a small stereo system.

In conducting a test, an officer gives a driver a mouth swab and has the driver rub it inside his mouth for a few minutes. The officer then places the swab inside the device and adds a vial of testing solution. The device provides results in about six to eight minutes.

2. Can a driver refuse a test?

Drivers have the right to refuse a mouth swab test. Law enforcement personnel cannot force a driver to take a test. An officer can ask a driver to submit to a test if the officer suspects that the driver has been using drugs. The driver can say “no.”

Note, however, that if a driver refuses the test, he may still be arrested for DUID if the officer suspects him to be under the influence of drugs. If arrested, the driver would be required to submit to a blood test.

A few symptoms of drug impairment include:

  • unsafe driving actions,
  • bloodshot eyes, and
  • the odor of marijuana in a vehicle.

3. Why is the MST used?

The test is used because other roadside tests, such as a breathalyzer test or a blood test, either do not detect the presence of drugs or are inefficient in doing so.

California DUI breath tests are used when a police officer suspects a driver is driving under the influence of alcohol. However, breath tests do not work in detecting drug use.

DUI Blood tests are used in DUI cases involving both alcohol and drugs. A problem with the blood tests, though, in relation to drug use, is that they are inefficient. It can take several weeks for a law enforcement agency to get the results back.

nurse mouth swab california dui
A mouth swab test can detect the presence of seven specific drugs.

4. What does a mouth swab test specifically detect?

There are two important things to note when discussing an MST and the issue of detection. These are:

  1. The tests detect the presence of seven drugs; and,
  2. The test cannot detect the levels of drugs that a person used.

4.1. Drugs detected

A mouth swab test can detect the presence of seven specific drugs. These are:

  1. marijuana,
  2. cocaine,
  3. opiates,
  4. methamphetamine,
  5. amphetamine,
  6. methadone, and
  7. benzodiazepines.

As for marijuana detection, THC can remain in a driver's system long after the effects of marihuana have gone away. Note, however, that the mouth swab test only detects active THC (or, delta-9 THC), which only remains in a person's system for several hours.

This means if a person used marijuana 24 hours prior to driving, active THC probably would not be detected by an MST, even though inactive THC may still be in the person's system.

4.2. Presence of drugs vs. level of drugs

While a mouth swab test can determine if drugs are in a driver's system, they cannot detect the level of drugs that were used. Blood tests are used to measure for particular levels.

Therefore, if a mouth swab test comes back positive, a driver must submit to a blood test so the law enforcement agency can know what levels of drugs were in a person's system.

5. What happens if there is a positive/negative result?

If a mouth swab test is positive for drug use, then the driver will most likely be arrested for suspicion of driving under the influence of drugs. And, the driver would be required to submit to a blood test.

If an MST is negative, this does not necessarily mean that a driver is free and clear of any charges or an arrest. The driver can still be arrested for DUID and forced to take a blood test if the officer suspects that the driver is high.

Please note that if a driver refuses to submit to a blood test, the police can get a warrant that will allow them to collect a sample. The driver will also be arrested for refusing to submit to a chemical test.

man arrested dui
California law has no “legal limit” for drugs in a person's system.

6. Does California have a “legal limit” for drugs and driving?

California law has no “legal limit” for drugs in a person's system. This is unlike California DUI cases where there is a precise blood alcohol concentration (BAC) level that indicates when a driver is driving illegally.

There is no legal limit for DUID cases because experts cannot agree what concentration of drugs in the bloodstream makes someone too impaired to drive.1

As the National Highway Traffic Safety Administration reports:

“[A]t the current time, specific drug concentration levels cannot be reliably equated with effects on driver performance.”2

So, California law simply states that it is illegal for someone to drive:

7. What are the penalties for driving under the influence of drugs?

DUID is a crime under California Vehicle Code 23152(f) and Vehicle Code 23152(g).

DUID is usually a misdemeanor in California. The penalties for misdemeanor DUID are the same as for driving under the influence of alcohol.

DUI penalties can include:

California Vehicle Code 23152(f) and 23152(g) can be charged as a felony if the following are true:

  1. it is the defendant's fourth DUI or subsequent DUI offense,
  2. the defendant has one prior felony DUI conviction, or
  3. the DUI caused injury to a third party.

Felony DUID can be punished by:

  • up to three years in jail (or 4 years if a third party was injured); and/or,
  • a fine of up to $1,000 (or up to $5,000 if someone was injured).

Were you accused of driving under the influence of drugs in California? Call us for help…

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Call us at (855) LAW-FIRM

If you or someone you know has been accused of driving under the influence of drugs, per Vehicle Code 23152, we invite you to contact us for a free consultation. We can be reached 24/7 at 855-LAWFIRM.


Legal References

  1. See, e.g., National Highway Traffic Safety Administration, “Drug-Impaired Driving: Understanding the Problem and Ways to Reduce It—A Report to Congress,” p 3: “[A]t the current time, specific drug concentration levels cannot be reliably equated with effects on driver performance.”

  2. See same.

  3. Vehicle Code 23152(f).

  4. Vehicle Code 23152(g).

  5. See Vehicle Code 23152(c): “(c) It is unlawful for a person who is addicted to the use of any drug to drive a vehicle. This subdivision shall not apply to a person who is participating in a narcotic treatment program approved pursuant to Article 3 (commencing with Section 11875) of Chapter 1 of Part 3 of Division 10.5 of the Health and Safety Code.”

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