Missouri’s drugged driving law is located at Missouri Revised Statutes Section 577.010. It states, "A person commits the crime of "driving while intoxicated" if he operates a motor vehicle while in an intoxicated or drugged condition." A person is in an "intoxicated condition" when he is under the influence of alcohol, a controlled substance, or drug, or any combination. (Section 577.001)
In other words, in Missouri it’s a crime to drive while under the influence of a drug. No blood testing standard is established in Missouri – that is, there is no fixed amount of drugs within the blood system that determines conviction. Whether a driver is impaired is determined on a case-by-case basis and at the discretion of the prosecutor.
Missouri’s drugged driving law is directed at the prohibition of controlled substances or drugs. A listing of controlled substances regulated by federal law are found at the Drug Enforcement Administration website. It’s not an acceptable defense to a drugged driving charge to claim that the driver is legally entitled to use the controlled substance.
A driver arrested for drugged driving in Missouri while be charged with driving under the influence and subject to DUI penalties. A conviction for drugged driving will be considered as a prior offense for purposes of calculating punishment regardless of whether a subsequent offense is due to alcohol or drugs. Read more about Missouri’s DUI laws.
Yes, there is an implied consent rule for blood, saliva, and urine testing. The refusal to take the test can be admitted into evidence against the driver.