Researchers have developed a variety of tests that are designed to determine whether a person is likely to be intoxicated. A police officer performs these tests on suspects after the officer has stopped a person on suspicion of drunk driving. These tests allow an officer to observe a suspect’s balance, physical ability, attention level, or other factors that the officer may use to determine whether the suspect is impaired. Officers often record a suspect’s performance of these tests, and this practice generally has been upheld on appeal.

In several states, authorities have set up checkpoints where officers can question drivers in an effort to catch drunk drivers. These checkpoints are often set up during holidays when people are more likely to drink, such as New Year’s Eve. Courts in the majority of states have upheld these checkpoints against challenges that these checkpoints are unconstitutional.