The Stages of DUI Detection Used By Police Officers

If you are stopped by a police officer who suspects you of driving under the influence of alcohol or drugs, events can seem like they’re happening at lightning speed. But the DUI detection process used by Florida law enforcement agencies involves a well-established series of steps that strongly influence the outcome of your criminal charge. 


The stages of a DUI investigation include these distinct activities: 


  1. Observing the vehicle in motion (establishing reasonable suspicion to a pull driver over) 
  2. Interacting personally with the driver (detecting signs of impairment) 
  3. Pre-arrest screening – field sobriety tests (to develop probable cause to arrest) 


When a driver observes the process, the course of activity looks spontaneous. But the officer is actually following a strict protocol that they’ve been trained to execute during any DUI investigation. Looking at each of the stages individually helps you understand precisely what the government needs to improve its likelihood of convicting the driver on a DUI charge. 



Observing the Vehicle in Motion 


The first step in a DUI investigation is the officer observing a vehicle in motion. The officer is trained to identify “suspicious” vehicle movements, such as speeding, moving too slowly, drifting between lanes, turning without signaling, and failing to comply with traffic control devices (red lights, stop signs, one-way streets, etc.). They also look for vehicles making dangerous maneuvers, tail gaiting, aggressive driving, cutting others off in traffic, and other scenarios that could threaten the lives or safety of others. 


Any one of these observations, and others too numerous to mention, could constitute “reasonable articulable suspicion” to stop the driver. The law requires that police have such a reasonable suspicion that a violation of the law is occurring before they have legal grounds to stop a motorist. The law considers a police officer pulling over a driver a “brief investigative detention.”  


At this early stage, the officer needs only a reasonable suspicion that some offense occurred. They need not yet suspect the driver is under the influence. Their suspicion for the stop could be based on any traffic infraction that violates a law or ordinance. 


An experienced DUI defense lawyer will find the grounds for the police stopping the driver to be extremely important. If the officer cannot articulate reasonable grounds for their suspicion of the driver, then the traffic stop can be ruled illegal, and evidence obtained through any illegal detention is inadmissible in court.  


If you have a skilled DUI defense lawyer, they will be able to identify insufficient legal grounds for a police traffic stop. The best criminal defense lawyers have a highly developed ability to “issue-spot.”  Spotting these subtle legal issues is what sets great criminal defense lawyers apart from those who recognize issues only after the case is over. 


Learn More > What is Probable Cause for a DUI in Florida  


Interacting Personally with the Driver 


Once an officer pulls over a driver, they still have work to do before they can arrest them for driving under the influence. So far, all the police may have is “reasonable suspicion.”  They need to have “probable cause” that a crime was committed before they can arrest the driver for DUI.  


During the police officer’s personal interaction with the driver, they will look for behavior or symptoms that confirm their initial suspicions. These could include a driver’s slurred speech, bloodshot eyes, unresponsive answers to questions, confusion about where they are or where they are going, a strong smell of alcohol or marijuana, clumsy handling of documents, or other noteworthy observations.  


These personal observations are important because the next stage in the DUI detection process will involve roadside field sobriety tests. But the officer needs a “reasonable suspicion” that the driver is under the influence before they can request that you perform these tests. It is during the personal interaction with the driver that the officer will gather the facts they need, if possible, to justify the field sobriety tests.  


Pre-Arrest Screening – Field Sobriety Tests 


If the officer develops enough evidence during the vehicle-in-motion and personal interaction with the driver to support a reasonable suspicion of DUI,  the officer will ask the driver to step out of the car and perform several physical tests known as Standardized Field Sobriety Tests (SFSTs).  


These tests were developed after years of research by experts at the National Highway Traffic Safety Administration (NHTSA). The tests were designed to determine if the driver could perform certain physical functions, including when their attention is divided. These divided attention tests require the person to use brain functions that are impaired when exposed to a certain quantity of alcohol in their bloodstream. 


Florida law does NOT require a driver to consent  

to any field sobriety tests. You can decline. 


The reason the officer wants to administer the field sobriety tests to a suspected drunk or drugged driver is to develop “probable cause” to arrest them. The SFSTs are generally accepted as evidence by courts in Florida and across the nation to establish probable cause to arrest a suspected driver under the influence of alcohol or drugs. 


The standard field sobriety tests include these: 

  • Walk and Turn Test 
  • One-Legged Stand Test 
  • Horizontal Gaze Nystagmus Test  


But there is more to these tests than you might think. Unless the officer administers each test according to the specific protocol set by the experts who designed the test, your lawyer can argue that the police officer’s scoring of the test is unreliable. These field sobriety tests are like scientific experiments, and if the experiment is not conducted in the same way each time, then the score is not valid. 


These tests actually begin before the driver thinks. The scoring includes whether the driver follows directions during the instruction period. That “divided attention” is key. But if the officer doesn’t give the proper instructions, then that portion of the test is invalid.  


Tampa Bay DUI Defense  


Only the most experienced DUI defense lawyers should be hired to defend your DUI charge. The veteran DUI defense lawyers at Stechschulte Nell, Attorneys at Law in Tampa have been concentrating on DUI law ever since Ben Stechschulte was a DUI prosecutor many years ago. Now he is one of the most experienced DUI defense lawyers in the Tampa – St. Petersburg area. 


Call us for a free DUI case review today at 813-280-1244. 


To learn more about how we can help

Contact us Today