I was recently arrested for DUI. The officer never witnessed me driving and was not in control of the vehicle. Do I have a chance of winning the case?

I was drinking with a group of friends. We became hungry so I decided to drive to a local grocery store. I went in with them, we bought our food, and walked out. We sat in my car, without the keys in the ignition, and ate the food we had just bought. About 5 min. later, police drove up to my car and told me the head of security at the store called them; I was told later the security called them because I allegedly almost rear-ended someone. I don't recall that almost happening. The officer put me through field sobriety tests and asked me to submit to the breathalyzer test - I refused. They searched my car and found an open container of alcohol (They didn't charge me for that). I didn't answer a single question he asked. He arrested me for DUI saying that because there was video footage of me driving into the lot that he had enough proof. Is that enough proof? Can I pose a defense stating that I started drinking after leaving the store and before the police arrived?