DWI – Developing Probable Cause To Arrest


The Driving While Impaired (DWI) arrest process involves three Phases. Each Phase is designed to help the investigating officer identify and gather evidence to determine whether there is probable cause to arrest the driver for DWI. These three Phases have been developed and designed by the National Highway Traffic Safety Administration.

Phase One – Vehicle In Motion.

  • The officer observes the vehicle in operation, determines whether to stop the vehicle, and observes the stopping sequence.
  • The officer is looking for motor vehicle violations (e.g. speeding, fail to stop for stop sign, stop light, crossing the centerline, etc.) or driving that suggest the driver may be under the influence of some impairing substance (e.g. weaving, swerving, driving below the speed limit, drifting, delayed reactions to stopping, starting inappropriately, unusual reactions to blue lights and officer’s authority, etc.).

Phase Two- Personal Contact.

  • The officer approaches the driver’s window and engages the driver face to face. The officer looks for signs of impairment that may include: red/glassy/glossy eyes, odors of alcohol/drugs, slurred/mumbled speech, slow reactions, etc., and open containers, controlled substances, or other contraband.
  • Based on these observations, the officer decides whether to ask the driver to exit the vehicle for further testing.
  • The officer observes how the driver exits and walks from the vehicle.

Phase Three – Pre-arrest Screening.

  • The officer administers standardized field sobriety tests (SFSTS) to determine whether there is probable causes to arrest the driver for DWI.
  • The SFSTS test the physical balance and coordination of the driver and whether the driver can mentally follow instructions. These tests are often referred to as “divided attention tests” because the driver has to focus on both mental (follow instructions) and physical tasks (perform the tests) at the same time.
  • The SFSTS include: One-Leg Stand; Walk and Turn; and Horizontal Gaze Nystagmus.
  • These tests should not be administered to drivers who are over the age of 65, have back, leg or inner ear problems, or who are overweight by 50 pounds or more.
  • The officer is looking for whether the driver follows the instructions as to how the test is performed and whether the driver physically performs each test correctly. Each failure to do so is noted as a “cue/clue” of impairment.
  • In addition to these three tests, the officer also may administer a preliminary breath test (PBT) using an Alco-sensor style device. Although a numerical figure is indicated after the driver submits a breath sample, the officer may only testify that he received a “+” or “-” result when establishing probable cause to arrest for DWI.

The officer uses the evidence gathered in each of these Phases to support the decision to arrest the driver for DWI.

Developments in North Carolina law enforcement techniques have made it easier for the State to obtain convictions in DWI cases. If you are arrested for DWI, it is vital to get an experienced DWI attorney to represent you. You need one who is familiar with the requirements in each Phase and how best to cross-examine and attack the officer’s opinion and decision to arrest for DWI. Often there is video evidence from in-car and body-cam recording devices that contradict the officer’s opinions. The officer and the State are reluctant to voluntarily share this type of evidence with the driver.

The Robinson Law Firm has over 30 years experience defending DWI cases.

Since 1995, Founder Les Robinson has been teaching other lawyers how to collect evidence and cross-examine officers to challenge and defeat the officer’s opinions on probable cause.

Contact The Robinson Law Firm immediately and get the help you need and deserve if you have been charged with DWI.

If you have any questions or inquiries about the process of a DWI charge, contact The Robinson Law Firm for a free consultation.

Categories: Blog, DWI, Law Enforcement, Probable Cause