What is the primary focus of phase three of the DUI investigation?

The primary focus of phase three of the DUI investigation is the pre-arrest screening process. During this phase, the law enforcement officer assesses the suspect's level of impairment based on a variety of observable behaviors, such as physical coordination, speech, and overall demeanor. This phase typically follows the initial observations made during the prior phases, where the officer evaluates driving patterns and then interacts with the driver.

In the pre-arrest screening process, officers often administer standardized field sobriety tests which help determine whether there is sufficient evidence of impairment to justify an arrest. This step is crucial as it directly informs the officer's decision regarding whether to proceed with an arrest for driving under the influence. Collecting reliable evidence at this stage can be foundational for any subsequent legal proceedings related to the DUI charge.

The other options, while related to traffic enforcement, do not encompass the primary focus of this specific phase in the DUI investigation. Traffic citations and vehicle inspections pertain to compliance with traffic laws and vehicle condition, while field sobriety checkpoints involve a systematic approach to identifying impaired drivers but are not focused on the individual assessment required in phase three. Thus, the emphasis in this phase lies squarely on evaluating the signs of intoxication and determining the need for arrest.