What is the primary function of an officer during Phase 3 of an OUI stop?

The primary function of an officer during Phase 3 of an OUI (Operating Under the Influence) stop is indeed pre-arrest screening. This phase involves assessing the driver's level of impairment and determining whether there is sufficient evidence to make an arrest for OUI. During this stage, the officer will typically conduct field sobriety tests to evaluate physical and cognitive functions impaired by alcohol or drugs. These tests help establish probable cause for arrest, allowing the officer to make an informed decision on whether to proceed with the arrest based on the driver's behavior and test results.

Conducting a breathalyzer test, while an important part of the overall OUI process, is typically done after the pre-arrest screening and is part of the evidentiary process rather than the initial assessment occurring in Phase 3. Issuing a citation and insurance verification are processes linked to different legal violations and are not the primary focus of an officer during the critical decision-making phase of assessing impairment. Therefore, pre-arrest screening stands out as the correct answer, as it directly pertains to the officer's responsibilities during that specific phase of the OUI stop.