Answer :
Final answer:
Officers need a reasonable suspicion to stop a vehicle but must establish probable cause to require a chemical test for DUI, except in the case of implied consent, which presumes consent to such tests as a condition of driving.
Explanation:
A DUI stop, an officer does not need probable cause or reasonable suspicion to administer a chemical test based on implied consent laws; these laws generally infer driver consent to such tests as a condition of operating a vehicle on state roads. However, for a police officer to legally stop a vehicle in the first place, they must have reasonable suspicion that the driver has violated a traffic law or is driving under the influence.
Once the vehicle is stopped, if the officer develops probable cause to believe that the driver is under the influence, they may then require a chemical test. The key difference here is that probable cause is a higher threshold than reasonable suspicion, and is needed for a more invasive search or seizure.
The relevant case law established by Terry v. Ohio (1968) indicates that police may stop and frisk individuals if they have reasonable suspicion, but probable cause is required to proceed further with searches or to justify an arrest for a DUI.
Moreover, anything in plain view, such as open containers of alcohol, may contribute to establishing probable cause. Chemical tests for DUI, under the implied consent precept, are considered a permissible seizure under the Fourth Amendment when an individual has been lawfully arrested for driving under the influence.
