Drug-impaired driving, in the context of its legal definition, is the act of driving a motor vehicle while under the influence of an impairing substance. DUID, or Driving Under the Influence of Drugs, is prohibited in many countries. Several American states and European countries now have "per se" DUID laws that presume a driver is impaired if they are found to have any detectable quantity of controlled substances in their body while operating an automobile and that the driver has no doctor's prescription for the substance. This is similar to the "per se" DUI/DWI laws that presume a driver is impaired when their blood alcohol content is above a certain level (currently 0.08% in most of the United States and 0.05% in Utah). There is some controversy with "per se" DUID laws in that a driver with any detectable quantity of controlled substances may not in fact be impaired and the detectable quantity in blood or sweat may be only the remnants of drug use in days or weeks past. It is against road traffic safety. Research on factors associated with engaging in DUID is receiving increasing attention to develop more effective countermeasures.
United States
According to the US National Highway Traffic Safety Administration's Drug Evaluation and Classification program (DEC), a drug is "any substance that, when taken into the human body, can impair the ability of the person to operate a vehicle safely." Under this definition, alcohol would be classified as a drug. For the purposes of this article, drug impaired driving is the use of drugs other than alcohol and the effect on driving.
Detection
Testing for alcohol concentration is performed using three methods – blood, breath, or urine. For law enforcement purposes, breath is the preferred method, since results are available almost instantaneously. Drug testing screens are typically performed in scientific laboratories so that the results will be admissible in evidence at trial.
Due to the overwhelming number of impairing substances that are not alcohol, drugs are classified into different categories for detection purposes. Drug impaired drivers still show impairment during the battery of standardized field sobriety tests, but there are additional tests to help detect drug impaired driving.
The Drug Evaluation and Classification program is designed to detect a drug impaired driver and classify the categories of drugs present in their system.
The DEC program breaks down detection into a 12-step process that a government-certified Drug Recognition Expert (DRE) can use to determine the category or categories of drugs that a suspect is impaired by. The 12 steps are
Breath Alcohol Test
Interview with Arresting Officer
Preliminary Evaluation
Evaluation of the Eyes
Psychomotor Tests
Vital Signs
Dark Room Examinations
Muscle Tone
Injection Sites
Interrogation of Suspect
Opinion of the Evaluator
Toxicological Examination
DREs are qualified to offer expert testimony in court that pertains to impaired driving on drugs. The use of the 12-step process is scientifically validated by numerous field studies.
Drug categories
The DEC program recognizes seven separate categories of impairing drugs:
CNS depressants – Drugs such as alcohol, barbiturates, and benzodiazepines fit in this category CNS stimulants – Drugs such as cocaine and amphetamines fit in this category Hallucinogens – Drugs such as LSD, peyote, and MDMA fit in this category Dissociative anesthetics – drugs such as PCP and Ketamine fit in this category Narcotic analgesics – synthetic and derivative opiates fit in this category Inhalants – volatile solvents, anesthetic gases and aerosol sprays fit in this category Cannabis – marijuana fits in this category
Laws
In the United States, 19 states have laws in effect that punish drug impaired driving. All states excluding West Virginia have a Drug Recognition Expert program. The following states have drug statutes enacted:
Alaska – Statute 28.35.030 – "(a) A person commits the crime of driving while under the influence of an alcoholic beverage, inhalant, or controlled substance if the person operates or drives a motor vehicle or operates an aircraft or a watercraft while under the influence of an alcoholic beverage, intoxicating liquor, inhalant, or any controlled substance, singly or in combination"