How Do Police Determine Whether A Driver Is Under The Influence Of Drugs Or Alcohol?

Police officers in Pennsylvania must have reasonable suspicion that a driver is committing a traffic violation or a crime before they can stop them. After an officer pulls you over, the officer will make observations and will investigate the reason for your stop.

If the officer suspects that you may be driving under the influence of alcohol or drugs, he or she might ask you several questions and perform tests.

These observations, questions, and tests are designed to help the officer establish probable cause to place you under arrest. Knowing how an officer determines that you are under the influence of alcohol or drugs is important and can help you to avoid making mistakes if you are pulled over.

If you have been charged with driving under the influence of drugs or alcohol in West Chester, DiCindio Law can advise you of the options that might be available to you.

Reasonable Suspicion For A Stop

Other than at a DUI checkpoint, a police officer cannot stop you unless he or she has a reasonable suspicion that you have violated a traffic law or have committed a crime. Reasonable suspicion must be based on objective facts and cannot be based on the officer’s hunch.

In other words, an officer can’t stop you for any reason but must have a good one. Some examples of what might provide a reason for an officer to make a DUI stop include the following:

  • Erratic driving
  • Speeding
  • Driving too slowly
  • Crossing the center line
  • Failing to maintain your lane
  • Failing to obey traffic control devices
  • Driving the wrong way
  • Striking objects on the side of the road

Officers can also stop your vehicle for any type of traffic violation and subsequently develop a reasonable suspicion that you might be under the influence of alcohol or drugs. For example, an officer might pull you over because of a burned-out headlamp.

After the officer walks up to your window and starts talking to you, he or she might decide to investigate you for a possible DUI if he or she makes observations that lead him or her to believe that you are under the influence.

Some of these types of observations might include the following:

  • Odor of alcohol, marijuana, or other drugs
  • Nervous or odd behavior
  • Fumbling when trying to retrieve your driver’s license
  • Bloodshot, watery eyes
  • Disheveled appearance
  • Alcohol bottles that are visible from the outside of the vehicle
  • Drug paraphernalia that is visible from the outside of the vehicle
  • Statements that you make
  • Slurred speech

Police officers commonly try to initiate a conversation as soon as they approach the window of a vehicle after a traffic stop. During this conversation, the officers will be listening, looking, and observing.

An officer will try to assess your ability to speak, keep eye contact, and exercise motor control. If he or she notices any of the signs that indicate that you might be under the influence of alcohol or drugs, the officer will take additional investigatory steps to develop probable cause to support your arrest.

Police Officers Need To Establish Probable Cause Before Making DUI Arrests

If an officer has a reasonable suspicion that you are driving under the influence of alcohol or drugs from your driving and other observations that he or she has made, the officer will start by asking specific questions. You might be asked if you have had anything to drink or if you have used drugs. The officer will then ask you to perform some field sobriety tests.

These are standardized tests that are administered by officers at the roadside and include the one-legged stand, the horizontal gaze nystagmus, and the walk and turn. If you agree to perform these tests, the officer will write down notes about your performance on each test.

You may be asked to submit to a preliminary breath test, which is a test of your breath performed by the officer using a portable device at the side of the road. If your PBT results indicate the presence of alcohol, the officer might then place you under arrest for a DUI. The probable cause to support your arrest will be based on the observations the officer made, your statements, your performance on the SFSTs, and your PBT results.

If your PBT results show that you are not under the influence of alcohol, the officer might call a drug recognition expert to the scene. This is a specially trained officer who has received training in recognizing the sciences of impairment by drugs.

That officer might perform some tests, and if you perform poorly on them, you may be placed under arrest. In that case, the officer’s probable cause to arrest you will be based on the officer’s observations of you and your driving and your performance on the DRE tests.

If the officer believes that you are under the influence of alcohol, the officer will take you to the jail or police station and ask you to submit to a breathalyzer test after your arrest. If the officer believes that you are under the influence of drugs, the officer will take you to a hospital to have your blood drawn.

When you drive in Pennsylvania, you are deemed to have given your implied consent for a breath or blood test. If you refuse these tests, you will face civil penalties and increased criminal penalties if you are convicted of a DUI offense.

Should You Answer An Officer’s Questions?

When you are pulled over, you are required to provide the officer with your driver’s license, registration, insurance information, and name. Beyond the basic details, you are not required to answer any questions. Resist the urge to try to talk yourself out of being arrested.

This does not work, and the statements that you make can be used against you at trial. If the officer asks you if you have had anything to drink, you can politely refuse to answer and tell the officer that you want an attorney. The fact that you choose to remain silent cannot be used against you in court.

While the officer might place you under arrest based on his or her other observations, the prosecutor will not have any incriminating statements to use against you.

The Field Sobriety Tests And The Preliminary Breath Test

Many people think that they have to perform the field sobriety tests when they are asked to do so by the police. You have the right to refuse the field sobriety and preliminary breath tests. You should avoid these tests because they are simply used by the officer to build probable cause and to add circumstantial evidence of your impairment.

If you refuse to talk, to perform field sobriety tests, and to submit to a preliminary breath test, the officer might still place you under arrest based on other observations that he or she has made, such as your driving, any odors that the officer smelled, your appearance, and your motor control when retrieving your license.

However, it will be more difficult for the prosecutor to meet the burden of proving your case beyond a reasonable doubt based solely on the initial observations made by the officer.

Searches Of Your Vehicle

If an officer sees alcohol bottles or drug paraphernalia from outside of your car, he or she can confiscate them as evidence since they were in plain view. If an officer does not have probable cause to believe that evidence of the crime for which you have been stopped will be discovered by searching your car, the officer will have to develop probable cause before searching or obtaining a search warrant.

If you are placed under arrest, the officer can search your person as a search incident to a lawful arrest. If an officer asks for your permission to search your vehicle, you do not have to agree. Consenting to a search is an exception to the warrant requirement. Officers sometimes ask for permission to search vehicles when they do not have sufficient probable cause to arrest people or to believe that evidence of crimes will be found inside of their cars.

Understanding Your Miranda Rights

Some people think that police officers must read their rights to them before asking any questions. The police do not have to Mirandize people that they have pulled over until after they take them into custody. Any statements that you make can be used against you, so be sure to avoid making incriminating statements to the officer.

After your arrest, assert your rights to remain silent and to have an attorney. Any questioning by the officer will then have to stop.

Submitting To Breath And Blood Tests

Unlike the preliminary breath and standardized field sobriety tests, you do not have the right to refuse a post-arrest breath, urine, or blood test. If you refuse, your license will be suspended for at least 12 months or longer if you have prior convictions.

People who are convicted of DUIs after refusing breath or blood tests will also face penalties for the highest BAC level. The prosecutor can also use your refusal of a breath or blood test against you at trial.

What Are The Police Allowed To Do During A Pennsylvania DUI Stop?

Police officers have the right to stop you if they witness you committing a traffic offense or if they reasonably believe that you are driving under the influence of drugs or alcohol or have committed another crime. Officers have the right to investigate whether you are driving while impaired, but they must also respect your rights.

Officers can stop motorists when they have a reasonable suspicion that they might be impaired or have committed a traffic violation. After the stop, officers can investigate further to determine whether to charge and arrest the motorists. Some of the permissible actions that an officer can take during an investigation include the following:

  • Ask for your driver’s license, name, registration, and insurance card
  • Ask about the reason why you were stopped
  • Ask if you have taken drugs or consumed alcohol
  • Ask where you are coming from
  • Ask your permission to search your car
  • Ask you to submit to a preliminary breath test and perform field sobriety tests
  • Ask you to submit to a post-arrest breath, blood, or urine test
  • Arrest you if the officer develops probable cause

While officers have numerous rights during investigations to allow them to secure evidence, they are required to follow certain laws and guidelines in how they carry out their actions. An experienced criminal defense lawyer at DiCindio Law can review how the officer investigated your case to determine whether the investigation was conducted properly. If there were problems, your lawyer might file motions to seek the suppression of some of the evidence against you.

Get Help From DiCindio Law

If you are charged with a DUI involving alcohol or drugs, you have legal rights. Criminal charges are not evidence that you have committed a crime, and there may be defenses that are available to you. Getting help from an experienced criminal defense and DUI attorney at DiCindio Law can allow you to learn about your rights and your legal options.

Michael DiCindio is a former prosecutor who understands how prosecutors and police build their cases. This helps him to anticipate what the prosecutor might argue and build strong defenses against the DUI charges that have been filed against his clients.

Contact Our DUI Law Firm in West Chester, PA

If you are facing criminal charges and need legal help, contact the West Chester, PA DUI lawyers at DiCindioLaw, LLC to schedule a free initial consultation.

DiCindio Law, LLC

29 S Walnut St
West Chester, PA 19382
(610) 430-3535

***This blog article is made available by the law firm publisher for educational purposes and to provide general information, not to provide specific legal advice. By reading, you understand that there is no attorney client relationship between you and the publisher. The above listed information does not include the entire crimes code, annotations, amendments or any recent changes that may be relevant. The information provided is for informational purposes only and may not reflect the most current legal developments. These materials are not intended, and should not be taken, as legal advice on any particular set of facts or circumstances. Please contact DiCindio Law, LLC for a consultation and to discuss what law is relevant to your case. ***