A driver’s blood alcohol content is usually a central factor in his or her drunk driving charge. North Carolina police officers also rely on other information when making DWI arrests. For example, field sobriety tests are fairly common during traffic stops for suspected drunk drivers. Also referred to as roadside sobriety tests, field sobriety tests involve a series of tasks aimed at evaluating drivers’ physical ability, balance and level of attention. There are three steps to the Standardized Field Sobriety Test — the SFST — that the National Highway Traffic and Safety administration — NHTSA — endorses, which are:

  • Horizontal gaze nystagmus — HGN
  • Walk and turn — WAT
  • One leg stand — OLS

The HGN test measures any involuntary eye jerking as a person moves his or her gaze from side to side. This jerking happens naturally to a certain extent, but is exaggerated in those who are under the influence of alcohol. Officers usually look for impairment in both eyes, and it is often noted as an inability to smoothly follow some type of moving object.

The WAT test measures whether a person can complete a task with divided attention. This involves having him or her walk a straight line heel to toe. The individual must then turn on just one foot and walk back to where he or she started, still walking heel to toe.

The OLS test measures a person’s physical ability. In this test, an officer will ask the driver to stand and raise one foot roughly 6 inches above the ground for a period of 30 seconds. If the individual uses his or her arms for balance, hops, sways or places the foot down, it may indicate impairment.

Drivers who fail the SFST will usually be asked to take a Breathalyzer test, designed to determine their BAC. However, even if a driver declines a Breathalyzer or registers a BAC below the legal limit of .08%, he or she could still be arrested and charged with a DWI. Understanding how field sobriety tests factor into these types of charges in North Carolina can be helpful for asserting a strong defense.