If you are pulled over because a Massachusetts law enforcement officer suspects you of drunk driving, the officer may require you to undergo a number of field sobriety tests to determine if your level of intoxication is apparent enough to warrant a breathalyzer or potential arrest for driving under the influence. But what are field sobriety tests, and what do typical ones entail?

The latest edition of the Massachusetts standard field test sobriety manual lists three common field tests used. The first is the HGN, or horizontal gaze nystagmus. The term “nystagmus” refers to a jitter that occurs in the eyes when looking to one side, and can be an indicator of the effects of alcohol on the central nervous system. According to the manual, distinct nystagmus and lack of smooth pursuit can both cause test failure on presumed grounds of intoxication. You may be more familiar with this as the pen test, in which an officer moves a pen slowly from side to side and asks you to follow it with your eyes while they monitor your eye movement.

Other tests focus on physical dexterity, such as the walk and turn and the one leg stand. In the walk and turn, you are asked to walk a straight line heel to toe, arms extended, before reaching a specified point, turning, and retracing your path by the same means. Wobbling, loss of balance, or other erratic movement may indicate intoxication to the officer. In the one leg stand test you will be asked to stand in a specified position with one leg raised while you count from 1,000 to 1,030. Losing count or touching your foot down from the expected stance may be cause for further investigation with a breathalyzer or other tests.

This information is for reference purposes only and should not be considered legally actionable.