Missouri police officers make traffic stops for various reasons, one of which might be suspected driver intoxication. If an officer sees a motorist veering over the yellow line, randomly applying brakes in a way that does not match current traffic flow or driving at night without headlights, that driver may be pulled over and asked the driver to exit the vehicle. What happens after that will determine whether the police officer makes a DUI arrest.
Missouri police must have probable cause to arrest a driver for suspected DUI. To determine if there is probable cause, it is common for a patrol officer to ask a motorist to take a field sobriety test. There are three tests that are most frequently administered during traffic stops — failing any one of them constitutes probable cause to arrest a driver for suspected intoxication.
Failing a walk-and-turn test may result in a DUI arrest
A police officer administering a walk-and-turn field sobriety test will ask a motorist to walk a straight line by placing the heel of one foot at the toe of the other with every step. It is also standard procedure to instruct the test taker to hold his or her arms out to the side at shoulder length while performing the test. Another type of field sobriety test police use to gauge balance and coordination is the one-leg stance test. While standing on one leg, a motorist may be told to tilt his or her head back and recite a series of numbers or letters while balancing on one leg.
Missouri police sometimes administer an eye test during a traffic stop
Intoxication can cause a person’s eyeballs to move erratically while tracking an object from left to right or vertically. When determining whether probable cause exists to make a DUI arrest, police may administer a horizontal gaze nystagmus test, during which the officer in question will closely monitor eye movements. Motorists are free to refuse to take field sobriety tests. If a driver takes a test and fails and is subsequently taken into police custody, he or she may request immediate legal assistance as the case is adjudicated in criminal court.