Legality of the Stop

A DUI cannot properly be premised on an illegal stop. For a stop to be legal the police need a legitimate basis for stopping the vehicle. In general, police need to be on duty and in proper police uniform to make a legal DUI stop (PSP troopers do not have to wear a hat). Accordingly, analyzing the stop is the starting point to evaluating all DUI cases. It is a fact specific analysis. Here, also, is where the complexity begins — determining if the police need probable cause or mere reasonable suspicion to stop a vehicle.

1. Probable Cause Traffic Stops - Speeding

​If it is not necessary to stop the vehicle to establish that a violation of the Vehicle Code has occurred, an officer must possess probable cause to stop the vehicle. Speeding stops are an example of a traffic stop requiring probable cause.
If a vehicle is stopped for speeding, the officer must possess probable cause to stop the vehicle. This is so because when a vehicle is stopped, nothing more can be determined as to the speed of the vehicle when it was observed while traveling upon a highway. Commonwealth v. Salter, 121 A.3d 987, 993 (Pa.Super. 2015).

2. Reasonable Suspicion Traffic Stops – Most DUI Stops

Where a violation is suspected, but a stop is necessary to further investigate whether a violation has occurred, an officer need only possess reasonable suspicion to make the stop.​

For example, if an officer possesses sufficient knowledge based upon behavior suggestive of DUI (e.g., swerving) the officer may stop the vehicle upon reasonable suspicion of a Vehicle Code violation, since a stop would provide the officer the needed opportunity to investigate further if the driver was operating under the influence of alcohol or a controlled substance.

3. Welfare Checks

A DUI case is sometimes charged following a welfare check. This happens when the police contact a person inside a vehicle to see if they need assistance or medical attention. For example, the police may check the status of a vehicle located in an otherwise empty parking lot, at night, with its headlights illuminated for a prolonged period.

4. Crash Investigations

Many DUI cases do not include a traffic stop or even a welfare check. DUI crashes are rarely observed by the police. In these cases, the initial police contact often occurs when the accused is in an ambulance or being treated on-scene by EMS. The police may make a request for a BAC test after observing clues of intoxication. Even when the police do not see the accused on-scene, the may request BAC testing upon observations made at the hospital. The police may also apply for a search warrant to test blood taken at a hospital or subpoena an accused’s medical records for prosecution.

5. Miranda Warnings

It is very common for those accused of a DUI to mention that they were not “read my rights” or given Miranda warnings prior to being arrested for suspicion of DUI. First, Miranda safeguards an accused from making incriminating statements, while in custody, during police interrogation. Statements made prior to an accused being held in custody typically fall outside Miranda’s protection. Second, even when Miranda is violated, the remedy is suppression of the statement at issue; not suppression of all the evidence (evidence of failed SFSTs or of BAC results would remain even if a Miranda violation occurred), nor dismissal of the case. Accordingly, Miranda does not offer relief in most DUI cases. While drivers have the right to remain silent, and may refuse to answer an officer’s questions or a request to perform SFSTs, drivers are required to display upon an officer’s demand: a driver’s license, registration documents, and proof of insurance. Further, in stops where only a citation is issued (non-DUI stops) a driver must write their name in the presence of the officer in order to provide identity.