What is Appreciable Impairment?

In order to prove a DWI charge, the state of North Carolina must prove three things: that the person charged with the crime of driving while impaired was, on the date alleged:


  1. first, driving a vehicle
  2. second, driving the vehicle upon a street, highway, or public vehicular area
  3. and third,
    1. either had any amount of a Schedule I substance in his system
    2. or had at a relevant time after the driving had a .08 BAC such that the alcohol had been consumed during or prior to driving,
    3. or had consumed a sufficient quantity of an impairing substance such that the person’s bodily or mental faculties had been appreciably impaired at the time of the driving.


Note that North Carolina law does not make it a crime to consume alcohol and drive, assuming the person is at least 21 years of age. And North Carolina law does even make it a crime to be impaired and drive, if that impairment is slight.

North Carolina law makes it a crime to be appreciably impaired and operate a vehicle on a street, highway, or other public vehicular area. Indeed, there is no conflation of driving under the influence and appreciable impairment, except that driving under the influence has always been defined, in North Carolina, as driving while appreciably impaired.

What is “appreciable impairment”? Case law in North Carolina defines appreciable impairment. The quintessential case is State v. Harrington, 336 SE 2d 852 (1985).

The facts are these: State Highway Patrol Trooper Davis saw Edward Harrington drive by at about 1:00 a.m. and began following him, originally because he saw a “state-owned” license plate on Harrington’s car. Davis followed Harrington about one-quarter of a mile, and observed him come to an abrupt stop, make a wide left turn, and weave between two southbound lanes. The defendant failed all four field sobriety tests, and had a blood alcohol concentration of .14 when tested 40 minutes later. Trooper Davis testified that the defendant told him he had four or five mixed drinks within four hours of the stop, and admitted being under the influence.

The Court of Appeals held that the State need not prove gross impairment or that the defendant is falling down drunk. But by the same token, the consumption of alcohol alone is not sufficient to indicate appreciable impairment. Nor is the mere smell of alcohol.

Impairment must be appreciable. Appreciable has been defined as noticeable and measurable.

Damon Chetson

Damon Chetson is a Board Certified Specialist in State and Federal Criminal Law. He represents people charged with serious and minor offenses in Raleigh, Wake County, and the Eastern District of North Carolina. Call (919) 352-9411.