There are rules and regulations that law enforcement officers must follow when conducting a sobriety checkpoint. First of all, these checkpoints must be made known to the public before they are conducted, such as by posting a notice about them online or in the newspaper. Officers may not choose individuals to investigate, but instead must follow a strict pattern, such as every other car or every third car. They must also have adequate grounds to make a DUI arrest instead of arresting anyone with slightly slurred speech or the supposed smell of alcohol on their breath. Use of a breathalyzer machine or of field sobriety tests can help an officer determine whether an individual is under the influence of alcohol or drugs. If these measures are not taken or if the tests are improperly administered, then the DUI arrest may be unlawful.