I pulled onto the shoulder to check my GPS because I thought I missed my exit (knowing it was safer to stop and read it than drive down the road and read it). While I was reading the directions, an officer pulled up behind me and asked me to roll the window down. He saw me stopped and said that, “as a courtesy,” he stopped to check on me. He said he smelled alcohol when I put my window down and I was charged with a DWI. Can an officer just approach my car like that?
You did not mention in your question whether the police officer activated his blue lights. Police officers are allowed to be courteous, and we encourage that. Officers can casually approach people in public places and speak any time they want. They cannot, however, use the blue lights to detain you and start an investigation unless the Officer has Reasonable Articulateable Suspicion that a crime is being committed. However, if he is not making any show of Governmental Authority- no blue lights, no sharp knock on the window, nothing that differentiates the officer from a concerned citizen stopping to check on you, then there is no violation of the 4th Amendment.
If the Officer put on blue lights, then you have been detained under the 4th Amendment. Whether this is a violation depends largely on where you were. A limited entrance interstate highway, or any other highway that prohibits stopping on the shoulder or only allows stopping for emergencies, will have the presumption that there was an emergency and you as the driver needed the officer. Under the Public Caretaker Doctrine, the officer used blue lights to protect the motoring public, and there is no 4th Amendment violation.
If you were on a state highway where stopping on the shoulder is not prohibited or limited, then the use of blue lights detains you (you would have been charged if you had driven off and ignored the blue lights). An officer cannot use the show of Governmental Authority (blue lights) to impose his “courtesy” upon someone else. Be aware that the District Attorney will try to lead the officer into stating it was for “Public Safety,” but if the officer will be honest and testify that he was being courteous but did not see an immediate threat to the motoring public, your lawyer should be able to fight the stop.