Under the influence is a term used to describe a state of intoxication which is criminal during certain activities, such as public intoxication or driving under the influence.
Laws and ordinances at the state and local levels, which vary by area, make public intoxication a crime. A person commits the crime of public intoxication if he appears in a public place under the influence of alcohol, narcotics or other drug to the degree that he endangers himself or another person or property, or by boisterous and offensive conduct annoys another person in his vicinity. A person may commit the offense of public intoxication by being under the influence of alcohol or drugs. This may include prescription drugs, over-the-counter medications or even aerosol sprays. It is a defense to prosecution for public intoxication that the alcohol or drugs were administered for therapeutic purposes and as part of the person's professional medical treatment by a licensed physician.
All states have laws against driving intoxicated, which vary by state. Legal intoxication is defined as a certain level of blood alcohol content (BAC), usually measurable at .10 or .08 percent. States that use the lower .08 BAC to define intoxication are eligible for more federal assistance, and therefore, there is a trend toward lowering the BAC limit.