A cop pulls a guy over one night for swerving in and out of lanes on the highway. He tells the guy to blow into a breathalyzer. "I can't do that, officer, I'm an asthmatic. I could get an asthma attack if I blow into that tube."
"OK, we'll just get a urine sample down at the station." "Can't do that either, officer. I'm a diabetic. I could get low blood sugar if I pee in a cup."
"Alright, we'll take a blood sample." "Can't do that either, officer. I'm a hemophiliac. If I give blood, I could die."
"Fine then, just walk this white line." "Can't do that either, officer." "Why not?"
"Because I'm drunk."