Can Police Arrest You for DUI Without Probable Cause in Arizona?
Being pulled over after having a drink does not automatically give police the right to arrest you for DUI.
Arizona law gives police officers considerable authority to investigate suspected impaired driving. But that authority has constitutional limits. An officer may have a lawful reason to pull you over. The officer may even have enough information to investigate whether you have been drinking. That does not necessarily mean the officer has probable cause to arrest you for DUI.
That distinction can become extremely important in a DUI case.
At AJB Law Firm, LLC, I represent people charged with DUI and other criminal offenses in Tucson and throughout Pima County. When reviewing a DUI arrest, I don't simply look at whether the police eventually obtained evidence suggesting alcohol or drug use. One of the questions I may ask is much more specific:
What did the officer actually know at the moment my client was arrested?
If the answer is "not enough," there may be a constitutional issue with the arrest and with evidence obtained as a result.
What Is Probable Cause for a DUI Arrest in Arizona?
The Fourth Amendment to the United States Constitution protects people against unreasonable searches and seizures. One of the protections flowing from the Fourth Amendment is the general requirement that police have probable cause before making an arrest.
Probable cause does not require police to already have enough evidence to prove a DUI beyond a reasonable doubt. That's the standard the prosecution ultimately faces at trial.
But probable cause requires more than a suspicion or hunch.
Generally speaking, the question is whether the facts and circumstances known to the officer would cause a reasonable person to believe that the suspect committed or was committing an offense.
In a DUI investigation, that means looking at the information available to the officer and asking whether it established probable cause to believe the driver was violating Arizona's DUI laws.
Importantly, courts generally look at the totality of the circumstances. There isn't necessarily one observation, one field sobriety test result, or one statement that automatically determines whether probable cause existed.
Reasonable Suspicion and Probable Cause Are Not the Same Thing
One of the most important concepts in evaluating a DUI arrest is the difference between reasonable suspicion and probable cause.
A DUI encounter can progress through several stages:
Traffic violation → traffic stop → DUI investigation → arrest
Different constitutional rules may apply at different stages.
For example, imagine an officer sees a driver commit a traffic violation. That observation may provide a lawful basis to stop the vehicle.
During the traffic stop, the officer smells alcohol.
That observation may lead the officer to investigate whether the driver has been drinking.
But here's the important part:
Evidence that justifies an investigation does not necessarily justify an arrest.
Alcohol itself is legal for adults to consume. A person can have a drink with dinner and legally drive home so long as that person is not impaired to the slightest degree and does not have an alcohol concentration prohibited by Arizona law.
The fact that an officer smells alcohol therefore doesn't necessarily answer the ultimate question.
The defense may need to examine what else the officer observed.
What Evidence Can Police Use to Establish Probable Cause for DUI?
There isn't a simple checklist that automatically establishes probable cause in every Arizona DUI case.
Depending on the circumstances, an officer might rely on evidence such as:
the person's driving behavior;
an accident or collision;
the odor of alcohol;
statements about drinking or drug use;
slurred speech;
bloodshot or watery eyes;
difficulty retrieving documents;
balance or coordination issues;
performance on field sobriety tests;
observations made while the driver exits or walks away from the vehicle;
a preliminary breath test, when applicable; or
other statements or observations during the investigation.
The important issue isn't simply how many observations appear in the police report.
The circumstances surrounding those observations matter.
For example, an officer may describe someone's eyes as red or watery. But that observation doesn't exist in a vacuum. Fatigue, allergies, environmental conditions, crying, contact lenses, or other circumstances may be relevant to evaluating what the observation actually proves.
Likewise, poor performance on a particular field sobriety exercise may look very different on body-camera footage than it sounds in a written police report.
That's one reason reviewing the actual evidence—not merely the officer's summary of it—can be so important in defending a DUI case.
When Does a DUI Investigation Become an Arrest?
This can be one of the most interesting issues in a DUI case.
Most people imagine an arrest occurring at a very specific moment:
"You're under arrest."
But constitutional law isn't necessarily that simple.
Courts look at the objective circumstances surrounding the encounter. A detention can potentially become the functional equivalent of an arrest before an officer formally announces the arrest.
Factors may include the extent to which the person's freedom has been restricted, the officer's display of authority, whether force or restraints were used, whether the person was moved to another location, and the overall circumstances of the encounter.
That can make the timeline extremely important.
Suppose an officer initially has reasonable suspicion sufficient to investigate a DUI. Police can't necessarily use that lesser standard to detain someone indefinitely while searching for enough evidence to eventually establish probable cause.
At some point, the nature of the detention may change.
And if the detention has effectively become an arrest, probable cause must already exist.
"But the Officer Said I Wasn't Under Arrest"
What happens if the officer tells someone:
"You're not under arrest."
That statement can certainly be relevant, but it doesn't necessarily resolve the constitutional question.
Courts generally look at what actually happened, rather than simply the terminology an officer used.
Imagine being told that you aren't under arrest while simultaneously being physically restrained, ordered to go somewhere with police, transported away from the scene, or otherwise subjected to restrictions normally associated with an arrest.
The question isn't merely what label police placed on the encounter.
The question is what a reasonable person in those circumstances would have understood was happening based upon the totality of the circumstances.
That distinction matters because police cannot avoid the probable-cause requirement merely by calling something an "investigative detention" if the actual circumstances have crossed the constitutional line into an arrest.
Why the Exact Timing of Probable Cause Matters
When analyzing a potential unlawful arrest, chronology matters.
A DUI defense attorney may need to identify:
When did the traffic stop begin?
What information did the officer have at that point?
When did the officer begin investigating DUI?
What observations occurred during that investigation?
When was the driver's freedom substantially restricted?
When did the detention become an arrest?
What facts did the officer know at that precise moment?
That final question can be critical.
Police generally cannot justify an arrest based upon information they obtained after the arrest occurred.
In other words, evidence discovered later cannot necessarily travel backward in time and provide probable cause that didn't exist when the arrest happened.
This is one reason timestamps, body-camera footage, dispatch records, and other evidence can matter considerably in DUI litigation.
The Police Report Isn't the Entire DUI Case
Police reports are important evidence, but they are written from the perspective of the investigating officer.
Whenever possible, I want to see the underlying evidence.
Depending on the case, that can include:
body-worn camera footage;
dash-camera footage;
dispatch and CAD records;
911 calls;
photographs;
field sobriety test video;
breath-testing records;
blood-testing records;
search warrants;
medical records when relevant; and
statements from witnesses.
A report might say that a driver "swayed" during a field sobriety test.
The video might allow the defense to evaluate how much the person actually moved.
A report might describe a driver as confused.
Body-camera footage might show the driver appropriately answering questions, following instructions, locating documents, and communicating normally.
Or the video might support what the officer wrote.
The point isn't to assume that a police officer is wrong.
It's to verify the evidence.
A useful principle in DUI defense is:
The police report tells us what the officer says happened. The video and timestamps may help establish what actually happened—and when.
What Happens If a DUI Arrest Was Not Supported by Probable Cause?
An unconstitutional arrest does not necessarily mean a DUI charge automatically disappears.
The appropriate remedy depends upon the circumstances of the case and the evidence at issue.
One important remedy for a Fourth Amendment violation is suppression of evidence.
Under what is commonly called the exclusionary rule, evidence obtained through an unconstitutional search or seizure may potentially be excluded from trial. Evidence subsequently discovered as a result of unlawful police conduct may also sometimes be challenged as "fruit of the poisonous tree."
That can matter significantly in a DUI prosecution.
For example, if evidence obtained after an unlawful arrest includes statements, test results, or other evidence the prosecution needs to establish its case, successfully suppressing that evidence could dramatically change the strength of the prosecution.
In some cases, suppression of critical evidence may leave the State unable to proceed.
But every case is different. The existence of a constitutional violation, the appropriate remedy, and its effect on the remaining charges require an individualized legal analysis.
What Does a Tucson DUI Attorney Look for When Reviewing Probable Cause?
A DUI defense shouldn't begin and end with the question:
"Was my client's BAC over the legal limit?"
There can be important issues long before a blood or breath result enters the picture.
When reviewing a DUI investigation, I may reconstruct the encounter from the beginning and examine questions such as:
Why was the vehicle stopped?
Did the officer actually observe the alleged traffic violation? Was there another lawful basis for the stop?
What caused the officer to expand the investigation?
What specific observations caused a routine traffic stop to become a DUI investigation?
What did the officer observe before the arrest?
It's important to distinguish evidence obtained before an arrest from evidence obtained afterward.
What does the video show?
Does body-camera or dash-camera footage support the officer's description of the driver's behavior and performance?
How long did the investigation last?
The duration and nature of the detention may matter when determining whether an investigatory detention became an arrest.
When exactly did the arrest occur?
The formal announcement isn't necessarily the only relevant moment.
What did the officer know at that time?
Ultimately, this may be the most important probable-cause question of all.
A DUI Arrest Is Not the Same Thing as a DUI Conviction
Being arrested for DUI can make it feel as though the important decisions have already been made.
They haven't.
An arrest is the beginning of a criminal case—not proof of guilt.
Arizona DUI cases can involve questions about the initial traffic stop, reasonable suspicion, probable cause, field sobriety testing, blood draws, breath testing, search warrants, laboratory procedures, constitutional rights, and the prosecution's ability to prove impairment or alcohol concentration beyond a reasonable doubt.
Sometimes the most important issue isn't what happened at the end of the investigation.
It's whether police had the legal authority to get there in the first place.
Arrested for DUI in Tucson or Pima County?
If you've been arrested for DUI, don't assume that an officer's decision to arrest you means the arrest was legally justified.
At AJB Law Firm, LLC, Tucson criminal defense attorney Amanda Bynum represents people accused of DUI and other criminal offenses. A DUI defense may involve reviewing the police reports, body-camera footage, field sobriety testing, officer observations, blood or breath evidence, and—critically—the timeline leading from the initial traffic stop to the eventual arrest.
The facts of every DUI case are different. Identifying potential defenses requires looking beyond the charge itself and examining how the evidence was actually obtained.
If you have been arrested for DUI in Tucson, Oro Valley, Marana, Sahuarita, Green Valley, or elsewhere in Pima County, contact AJB Law Firm to schedule a consultation and discuss the specific circumstances of your case.
This article is provided for general informational purposes only and is not legal advice. Reading this article does not create an attorney-client relationship.
