Criminal Law Questions? Ask a Criminal Lawyer.
While an officer can prove a DUI in court without a breathalyzer test (based on observations only--bloodshot eyes, slurred speech, unsteady gait, smell of alcohol, etc.), it is unlikely that he is going to go forward against you at this point. First of all, it is much easier to prove a DUI with a breath result, so if he wanted to proceed against you, he would have asked you to take the test. And second, officers are not supposed to let drunk people get back in their cars and carry on driving as a matter of public safety. So if he truly thought you were drunk and wanted to pursue a DUI charge, he likely would not have let you go, because he could get in trouble with his job for that. Thus, I think at this point that while he possibly could charge you for a DUI later, it is highly unlikely.